const std = @import("std");
const pardes = @import("pardes");
const panes = pardes.panes;
const layout = pardes.layout;
const Pardes = pardes.Pardes;
const Pane = pardes.Pane;
const Key = pardes.Key;
const config = pardes.config;
const modal = pardes.modal;
const dump = pardes.dump;
const image = pardes.image;
const syntax = pardes.syntax;
const filesystem = pardes.filesystem;

const TagNavigationTests = struct {
    fn key(p: *Pardes, cp: u21) void {
        p.update(.{ .key = .{ .cp = cp } });
    }

    fn enterNormal(p: *Pardes) *Pane {
        key(p, ':');
        return p.panes[p.active].?;
    }

    test "tag navigation retains each pane cursor and mouse placement overrides memory" {
        const p = try Pardes.init(std.testing.allocator, .{ .tty_only = true, .cols = 100, .rows = 20 });
        defer p.deinit();
        const first = try p.setTestFile("body\n");
        p.presentation.enabled = false;
        try std.testing.expect(p.executeBuiltinLine(0, "New"));
        const second_id = p.active;
        const second = p.panes[second_id].?;
        try std.testing.expect(layout.splitColumn(p, second_id, second_id, false));
        p.update(.tick);
        p.active = 0;
        key(p, ':');
        key(p, Key.home);
        for (0..3) |_| key(p, Key.right);
        const first_col = first.tag_col;
        key(p, Key.escape);
        p.active = second_id;
        key(p, ':');
        key(p, Key.home);
        for (0..5) |_| key(p, Key.right);
        const second_col = second.tag_col;
        key(p, Key.escape);
        p.active = 0;
        key(p, ':');
        try std.testing.expectEqual(first_col, first.tag_col);
        key(p, Key.escape);
        p.active = second_id;
        key(p, ':');
        try std.testing.expectEqual(second_col, second.tag_col);
        key(p, Key.escape);
        var frame = std.heap.ArenaAllocator.init(p.gpa);
        defer frame.deinit();
        _ = try p.render(frame.allocator());
        const rect = p.rects[0];
        const y = if (p.settings.tag_bottom) rect.y + rect.h - pardes.BOX_H else rect.y;
        ClickCursorTests.click(p, .left, rect.x + config.GUTTER + 6, y);
        try std.testing.expectEqual(@as(usize, 0), p.active);
        try std.testing.expectEqual(@as(u16, 6), first.tag_col);
        key(p, Key.escape);
        p.startPrompt(first, .{ .search = config.search_marker });
        key(p, Key.escape);
        key(p, ':');
        try std.testing.expectEqual(@as(u16, 6), first.tag_col);
        key(p, Key.escape);
        try std.testing.expectEqualStrings("body\n", first.file.?.content);
    }

    test "tag navigation clamps remembered columns to renamed graphemes and shorter tags" {
        const p = try Pardes.init(std.testing.allocator, .{ .tty_only = true, .cols = 80, .rows = 14 });
        defer p.deinit();
        const pane = try p.setTestFile("body\n");
        key(p, ':');
        key(p, Key.home);
        for (0..3) |_| key(p, Key.right);
        key(p, Key.escape);
        p.gpa.free(pane.file.?.path);
        pane.file.?.path = try p.gpa.dupe(u8, "/界.zig");
        key(p, ':');
        try std.testing.expectEqual(@as(u16, 1), pane.tag_col);
        key(p, Key.end);
        key(p, Key.escape);
        p.gpa.free(pane.file.?.path);
        pane.file.?.path = try p.gpa.dupe(u8, "/é");
        pane.tag_tail_len = 0;
        key(p, ':');
        try std.testing.expectEqual(@as(u16, 3), pane.tag_col);
        try std.testing.expectEqualStrings("body\n", pane.file.?.content);
    }

    test "tag navigation J and K restore cursors in stacked panes" {
        for ([_]bool{ false, true }) |bottom| {
            const p = try Pardes.init(std.testing.allocator, .{ .tty_only = true, .cols = 80, .rows = 24 });
            defer p.deinit();
            const first = try p.setTestFile("body\n");
            p.presentation.enabled = false;
            p.settings.tag_bottom = bottom;
            try std.testing.expect(p.executeBuiltinLine(0, "New"));
            const second_id = p.active;
            const second = p.panes[second_id].?;
            p.update(.tick);
            p.active = 0;
            _ = enterNormal(p);
            key(p, Key.home);
            key(p, 'l');
            key(p, 'l');
            key(p, 'J');
            try std.testing.expectEqual(second_id, p.active);
            try std.testing.expect(!first.tag_edit and second.tag_edit);
            key(p, Key.home);
            for (0..4) |_| key(p, 'l');
            key(p, 'K');
            try std.testing.expectEqual(@as(usize, 0), p.active);
            try std.testing.expectEqual(@as(u16, 2), first.tag_col);
            key(p, 'J');
            try std.testing.expectEqual(second_id, p.active);
            try std.testing.expectEqual(@as(u16, 4), second.tag_col);
        }
    }

    test "tag navigation uses uppercase pane and header keys while lowercase stays local" {
        for ([_]bool{ false, true }) |bottom| {
            const p = try Pardes.init(std.testing.allocator, .{ .tty_only = true, .cols = 100, .rows = 20 });
            defer p.deinit();
            _ = try p.setTestFile("body\n");
            p.presentation.enabled = false;
            p.settings.tag_bottom = bottom;
            p.settings.column_tags = true;
            try std.testing.expect(p.executeBuiltinLine(0, "New"));
            const right = p.active;
            try std.testing.expect(layout.splitColumn(p, right, right, false));
            p.update(.tick);
            p.active = 0;
            const pane = enterNormal(p);
            key(p, Key.home);
            key(p, 'l');
            try std.testing.expectEqual(@as(u16, 1), pane.tag_col);
            key(p, 'h');
            key(p, 'k');
            try std.testing.expectEqual(@as(u16, 0), pane.tag_col);
            try std.testing.expectEqual(@as(usize, 0), p.active);
            try std.testing.expect(pane.tag_edit and p.topbar_col == null);
            key(p, 'L');
            try std.testing.expectEqual(right, p.active);
            try std.testing.expect(!pane.tag_edit and p.panes[right].?.tag_edit);
            key(p, 'H');
            try std.testing.expectEqual(@as(usize, 0), p.active);
            key(p, 'K');
            try std.testing.expect(p.topbar_col != null and p.header_column != null);
            try std.testing.expect(!pane.tag_edit);
            key(p, 'l');
            const column_cursor = p.topbar_col.?;
            key(p, 'K');
            try std.testing.expect(p.topbar_col != null and p.header_column == null);
            key(p, 'l');
            key(p, 'l');
            const workspace_cursor = p.topbar_col.?;
            key(p, 'J');
            try std.testing.expect(p.topbar_col != null and p.header_column != null);
            try std.testing.expectEqual(column_cursor, p.topbar_col.?);
            key(p, 'K');
            try std.testing.expectEqual(workspace_cursor, p.topbar_col.?);
            key(p, 'J');
            key(p, 'J');
            try std.testing.expect(p.topbar_col == null and pane.tag_edit);
            key(p, 'j');
            try std.testing.expect(!pane.tag_edit and p.topbar_col == null);
            try std.testing.expectEqual(@as(usize, 0), p.active);
            _ = enterNormal(p);
            key(p, 'K');
            key(p, 'j');
            try std.testing.expect(p.topbar_col == null and !pane.tag_edit);
            key(p, ':');
            key(p, 'i');
            key(p, Key.end);
            const before = pane.tag_tail_len;
            try std.testing.expect(pane.tag_edit and pane.mode == .insert);
            for ("hjklHJKL") |letter| {
                const text = [_]u8{letter};
                p.update(.{ .key = .{ .cp = letter, .text = &text } });
                try std.testing.expect(pane.tag_edit and pane.mode == .insert);
            }
            try std.testing.expectEqualStrings("hjklHJKL", pane.tag_tail[before..pane.tag_tail_len]);
            try std.testing.expect(pane.tag_edit and pane.mode == .insert and p.topbar_col == null);
            try std.testing.expectEqual(@as(usize, 0), p.active);
        }
    }
};

const BodyHitTests = struct {
    fn mouse(layer: *const pardes.BodyLayer, row: u16, col: u16, kind: pardes.Mouse.Kind) pardes.Mouse {
        const width: f32 = if (row < layer.context_rows) 8 else 10;
        const x = @as(f32, @floatFromInt(layer.viewport.x)) * 10 + (@as(f32, @floatFromInt(col)) + 0.5) * width;
        const y = layer.rowTop(row, 20, 10) + layer.rowHeight(row, 20, 10) / 2;
        return .{ .button = .left, .kind = kind, .col = @intFromFloat(x / 10), .row = @intFromFloat(y / 20), .body_hit = layer.hitAt(x, y, 10, 20, 8, 10).? };
    }

    test "compact TreeContext mouse follows source rows in reclaimed space" {
        if (!syntax.enabled) return error.SkipZigTest;
        const p = try Pardes.init(std.testing.allocator, .{ .tty_only = true, .cols = 64, .rows = 18 });
        defer p.deinit();
        p.row_metrics = .{ .body_w = 10, .body_h = 20, .tagline_w = 8, .tagline_h = 10 };
        const pane = try TreeContextTests.setZigFile(p, "const Box = struct {\n    pub fn work(\n        value: usize,\n    ) void {\n" ++ "        // body\n" ** 60 ++ "    }\n};\n");
        try std.testing.expect(p.executeBuiltinLine(0, "TreeContext"));
        pane.scrollBy(10);
        var frame = std.heap.ArenaAllocator.init(p.gpa);
        defer frame.deinit();
        _ = try p.render(frame.allocator());
        const layer = &p.surface.body_layers[0];
        try std.testing.expect(layer.context_rows >= 4);
        try std.testing.expect(layer.rows > pane.rows);
        const first = mouse(layer, 0, 2, .press);
        const second = mouse(layer, 1, 2, .press);
        try std.testing.expectEqual(first.row, second.row);
        const top = pane.scroll();
        for ([_]u16{ 0, 1 }) |row| {
            const expected = pane.wrapAt(row).line;
            p.update(.{ .mouse = mouse(layer, row, 2, .press) });
            p.update(.{ .mouse = mouse(layer, row, 2, .release) });
            try std.testing.expectEqual(expected, pane.cur_row);
            try std.testing.expectEqual(top, pane.scroll());
        }
        const last = pane.body_visible_rows - 1;
        try std.testing.expect(last >= pane.rows);
        const expected = pane.wrapAt(last).line;
        const prefix = panes.File.gutterWidth(pane);
        p.update(.{ .mouse = mouse(layer, last - 1, prefix + 11, .press) });
        // Release at a different source row without an intermediate drag event.
        p.update(.{ .mouse = mouse(layer, last, prefix + 14, .release) });
        try std.testing.expectEqualStrings("body\nbody", pardes.test_api.heldSelection(p, 0).?);
        p.update(.{ .mouse = mouse(layer, last, 10, .press) });
        p.update(.{ .mouse = mouse(layer, last, 10, .release) });
        try std.testing.expectEqual(expected, pane.cur_row);
        var stale = mouse(layer, 0, 2, .press);
        stale.body_hit.?.serial +%= 1;
        p.update(.{ .mouse = stale });
        try std.testing.expectEqual(expected, pane.cur_row);
        p.update(.{ .key = .{ .cp = 'i' } });
        p.update(.{ .key = .{ .cp = 'X', .text = "X" } });
        try std.testing.expect(std.mem.indexOfScalar(u8, modal.lineSlice(pane.file.?.content, @intCast(expected)), 'X') != null);
    }
};

const TreeContextTests = struct {
    const source = "const Box = struct {\n" ++
        "    pub fn work(\n" ++
        "        value: usize,\n" ++
        "    ) void {\n" ++
        "        _ = value;\n" ++
        "        // one\n" ++
        "        // two\n" ++
        "        // three\n" ++
        "        // four\n" ++
        "        // five\n" ++
        "        // six\n" ++
        "    }\n" ++
        "};\n";

    fn setZigFile(p: *Pardes, content: []const u8) !*Pane {
        const pane = try p.setTestFile(content);
        p.gpa.free(pane.file.?.path);
        pane.file.?.path = try p.gpa.dupe(u8, "/tree-context.zig");
        p.presentation.enabled = false;
        return pane;
    }

    test "TreeContext Look to an open file discards the old viewport extent" {
        for ([_]bool{ false, true }) |context| {
            if (context and !syntax.enabled) continue;
            const p = try Pardes.init(std.testing.allocator, .{ .tty_only = true, .cols = 64, .rows = 18 });
            defer p.deinit();
            const pane = try setZigFile(p, "pub fn work() void {\n" ++ "    // body\n" ** 100 ++ "}\n");
            if (context) try std.testing.expect(p.executeBuiltinLine(0, "TreeContext"));
            var frame = std.heap.ArenaAllocator.init(p.gpa);
            defer frame.deinit();
            _ = try p.render(frame.allocator());
            try std.testing.expectEqual(@as(i32, 0), pane.scroll());
            p.lookAt(0, "/tree-context.zig:60");
            try std.testing.expectEqual(@as(usize, 0), p.active);
            try std.testing.expectEqual(@as(i32, 59), pane.cur_row);
            const surface = try p.render(frame.allocator());
            const visible = pane.wrapRow(pane.cur_row, pane.cur_col);
            try std.testing.expect(visible.row >= pane.context_rows);
            try std.testing.expect(visible.row < pane.rows);
            try std.testing.expectEqual(@as(i32, 59), pane.wrapAt(visible.row).line);
            const cursor = surface.cursor orelse return error.MissingLookCursor;
            const rect = p.rects[0];
            const y = if (p.settings.tag_bottom) rect.y else rect.y + pardes.BOX_H;
            try std.testing.expectEqual(y + @as(u16, @intCast(visible.row)), cursor.y);
        }
    }

    test "TreeContext sticky declarations preserve the body while clicked and edited" {
        if (!syntax.enabled) return error.SkipZigTest;
        const p = try Pardes.init(std.testing.allocator, .{ .tty_only = true, .cols = 64, .rows = 18 });
        defer p.deinit();
        const pane = try setZigFile(p, source);
        var frame = std.heap.ArenaAllocator.init(p.gpa);
        defer frame.deinit();
        pane.scrollBy(7);
        _ = try p.render(frame.allocator());
        try std.testing.expectEqual(@as(u16, 0), pane.context_rows);
        try std.testing.expect(p.executeBuiltinLine(0, "TreeContext"));
        _ = try p.render(frame.allocator());
        try std.testing.expectEqual(@as(u16, 4), pane.context_rows);
        for (0..4) |row| try std.testing.expectEqual(@as(i32, @intCast(row)), pane.wrapAt(@intCast(row)).line);
        try std.testing.expectEqual(@as(i32, 7), pane.wrapAt(pane.context_rows).line);
        const rect = p.rects[0];
        const x = rect.x + config.GUTTER + panes.File.gutterWidth(pane);
        const y = if (p.settings.tag_bottom) rect.y else rect.y + pardes.BOX_H;
        ClickCursorTests.click(p, .left, x + 6, y);
        try std.testing.expectEqual(@as(i32, 0), pane.cur_row);
        try std.testing.expectEqual(@as(i32, 6), pane.cur_col);
        try std.testing.expectEqual(@as(i32, 7), pane.scroll());
        const cursor = (try p.render(frame.allocator())).cursor orelse return error.MissingContextCursor;
        try std.testing.expectEqual(x + 6, cursor.x);
        try std.testing.expectEqual(y, cursor.y);
        p.update(.{ .key = .{ .cp = 'i' } });
        p.update(.{ .key = .{ .cp = 'Z', .text = "Z" } });
        try std.testing.expect(std.mem.startsWith(u8, pane.file.?.content, "const ZBox = struct {"));
        try std.testing.expectEqual(@as(i32, 7), pane.scroll());
        _ = try p.render(frame.allocator());
        try std.testing.expectEqual(@as(u16, 4), pane.context_rows);
        p.update(.{ .key = .{ .cp = Key.escape } });
        var previous: u16 = pane.context_rows;
        while (pane.scroll() > 0) {
            pane.scrollBy(-1);
            _ = try p.render(frame.allocator());
            try std.testing.expect(pane.context_rows <= previous);
            previous = pane.context_rows;
            try std.testing.expectEqual(pane.scroll(), pane.wrapAt(pane.context_rows).line);
        }
        try std.testing.expectEqual(@as(u16, 0), pane.context_rows);
        try std.testing.expectEqual(@as(i32, 0), pane.wrapRow(0, pane.cur_col).row);
        try std.testing.expect(p.executeBuiltinLine(0, "TreeContext"));
        pane.scrollBy(7);
        _ = try p.render(frame.allocator());
        try std.testing.expectEqual(@as(u16, 0), pane.context_rows);
    }

    test "TreeContext unwrapped headers map Unicode and survive source replacement" {
        if (!syntax.enabled) return error.SkipZigTest;
        const p = try Pardes.init(std.testing.allocator, .{ .tty_only = true, .cols = 48, .rows = 14 });
        defer p.deinit();
        const pane = try setZigFile(p, "pub fn @\"界name\"(\n\tvalue: usize,\n) void {\n" ++ "    _ = value;\n" ** 12 ++ "}\n");
        p.settings.wrap = false;
        p.settings.colors = false;
        try std.testing.expect(p.executeBuiltinLine(0, "TreeContext"));
        pane.scrollBy(8);
        pane.hscroll = 4;
        var frame = std.heap.ArenaAllocator.init(p.gpa);
        defer frame.deinit();
        const surface = try p.render(frame.allocator());
        try std.testing.expectEqual(@as(u16, 3), pane.context_rows);
        const rect = p.rects[0];
        const y = if (p.settings.tag_bottom) rect.y else rect.y + pardes.BOX_H;
        var glyph_x: ?u16 = null;
        for (0..surface.cols) |col| {
            if (std.mem.eql(u8, surface.at(@intCast(col), y).grapheme(), "界")) glyph_x = @intCast(col);
        }
        const x = glyph_x orelse return error.MissingContextUnicode;
        ClickCursorTests.click(p, .left, x + 1, y);
        try std.testing.expectEqual(@as(i32, 0), pane.cur_row);
        try std.testing.expectEqual(@as(i32, 9), pane.cur_col);
        try std.testing.expectEqual(@as(i32, 8), pane.scroll());
        const cursor = (try p.render(frame.allocator())).cursor orelse return error.MissingContextCursor;
        try std.testing.expectEqual(x, cursor.x);
        try std.testing.expectEqual(y, cursor.y);
        panes.File.setContent(p, &pane.file.?, try p.gpa.dupe(u8, "// no enclosing declaration\n" ** 18));
        _ = try p.render(frame.allocator());
        try std.testing.expectEqual(@as(u16, 0), pane.context_rows);
        try std.testing.expectEqual(pane.scroll(), pane.wrapAt(0).line);
    }

    test "TreeContext clipped headers leave wrapped body cursor coordinates intact" {
        if (!syntax.enabled) return error.SkipZigTest;
        const p = try Pardes.init(std.testing.allocator, .{ .tty_only = true, .cols = 24, .rows = 12 });
        defer p.deinit();
        const body = "    // 012345678901234567890123456789界tail";
        const pane = try setZigFile(p, "pub fn aLongDeclarationNameThatCannotFit() void {\n    // before\n" ++ body ++ "\n}\n");
        p.settings.wrap = true;
        try std.testing.expect(p.executeBuiltinLine(0, "TreeContext"));
        pane.scrollBy(2);
        var frame = std.heap.ArenaAllocator.init(p.gpa);
        defer frame.deinit();
        const surface = try p.render(frame.allocator());
        try std.testing.expectEqual(@as(u16, 1), pane.context_rows);
        try std.testing.expectEqual(@as(i32, 2), pane.wrapAt(1).line);
        try std.testing.expectEqual(@as(i32, 2), pane.wrapAt(2).line);
        var target: ?struct { x: u16, y: u16 } = null;
        for (0..surface.rows) |row| for (0..surface.cols) |col| {
            if (std.mem.eql(u8, surface.at(@intCast(col), @intCast(row)).grapheme(), "界"))
                target = .{ .x = @intCast(col), .y = @intCast(row) };
        };
        const glyph = target orelse return error.MissingWrappedContextBody;
        ClickCursorTests.click(p, .left, glyph.x + 1, glyph.y);
        try std.testing.expectEqual(@as(i32, 2), pane.cur_row);
        try std.testing.expectEqual(@as(i32, @intCast(std.mem.indexOf(u8, body, "界").?)), pane.cur_col);
        const cursor = (try p.render(frame.allocator())).cursor orelse return error.MissingContextBodyCursor;
        try std.testing.expectEqual(glyph.x, cursor.x);
        try std.testing.expectEqual(glyph.y, cursor.y);
    }
};

const TtySelectionTests = struct {
    fn noChildInput(p: *Pardes) !void {
        while (p.nextEffect()) |effect| {
            if (effect == .write) return error.UnexpectedChildInput;
            if (effect == .set_clipboard) p.perform(effect);
        }
    }

    test "tty selection yields to a new modal cursor selection" {
        if (comptime !panes.Terminal.enabled) return error.SkipZigTest;
        const p = try Pardes.init(std.testing.allocator, .{ .tty_only = true, .cols = 40, .rows = 12 });
        defer p.deinit();
        p.presentation.enabled = false;
        const pane = p.panes[0].?;
        pane.tty_filter = false;
        while (p.nextEffect()) |_| {}
        p.update(.{ .output = .{ .pane = 0, .bytes = "alpha" } });
        var frame = std.heap.ArenaAllocator.init(p.gpa);
        defer frame.deinit();
        _ = try p.render(frame.allocator());
        const rect = p.rects[0];
        const x = rect.x + config.GUTTER;
        const y = if (p.settings.tag_bottom) rect.y else rect.y + pardes.BOX_H;
        JumpSelectionTests.drag(p, x + 1, y, x + 3, y);
        try std.testing.expectEqualStrings("lph", p.yank orelse return error.MissingAutomaticTtyYank);
        p.update(.{ .key = .{ .cp = p.opts.tty_toggle, .ctrl = true } });
        p.update(.{ .key = .{ .cp = 'l' } });
        try std.testing.expectEqual(@as(i32, 4), pane.cur_col);
        p.update(.{ .key = .{ .cp = 'y' } });
        try std.testing.expectEqualStrings("a", p.yank.?);
        try noChildInput(p);
    }

    test "tty selection preserves exact rectangle through yank clipboard and mode changes" {
        if (comptime !panes.Terminal.enabled) return error.SkipZigTest;
        for ([_]bool{ false, true }) |prompt| {
            const p = try Pardes.init(std.testing.allocator, .{ .tty_only = true, .cols = 40, .rows = 12 });
            defer p.deinit();
            const pane = p.panes[0].?;
            pane.mode = .tty;
            pane.tty_filter = false;
            p.presentation.enabled = false;
            while (p.nextEffect()) |_| {}
            p.update(.{ .output = .{ .pane = 0, .bytes = if (prompt)
                "\x1b]133;A\x07$ \x1b]133;B\x07abc"
            else
                "alpha\r\nbravo" } });
            var frame = std.heap.ArenaAllocator.init(p.gpa);
            defer frame.deinit();
            _ = try p.render(frame.allocator());
            const rect = p.rects[0];
            const x = rect.x + config.GUTTER;
            const y = if (p.settings.tag_bottom) rect.y else rect.y + pardes.BOX_H;
            JumpSelectionTests.drag(p, x + @as(u16, if (prompt) 0 else 1), y, x + 3, y + @as(u16, if (prompt) 0 else 1));
            const expected = if (prompt) "$ ab" else "lph\nrav";
            try std.testing.expectEqual(Pane.Mode.tty, pane.mode);
            try std.testing.expectEqualStrings(expected, pardes.test_api.heldSelection(p, 0).?);
            try std.testing.expectEqualStrings(expected, p.yank orelse return error.MissingAutomaticTtyYank);
            try noChildInput(p);

            try std.testing.expect(p.executeBuiltinLine(0, "ClipYank"));
            try noChildInput(p);
            try std.testing.expectEqualStrings(expected, p.fallback.clipboard.items);
            p.update(.{ .key = .{ .cp = p.opts.tty_toggle, .ctrl = true } });
            try std.testing.expectEqual(Pane.Mode.normal, pane.mode);
            const normal = try p.render(frame.allocator());
            if (!prompt) {
                const selection_bg: pardes.Color = .{ .rgb = p.theme().sel_bg };
                try std.testing.expect(!std.meta.eql(selection_bg, normal.at(x + 4, y).style.bg));
                try std.testing.expect(!std.meta.eql(selection_bg, normal.at(x, y + 1).style.bg));
            }
            try std.testing.expectEqualStrings(expected, pardes.test_api.heldSelection(p, 0).?);
            p.update(.{ .key = .{ .cp = 'y' } });
            try std.testing.expectEqualStrings(expected, p.yank.?);
            try noChildInput(p);
            p.update(.{ .key = .{ .cp = p.opts.tty_toggle, .ctrl = true } });
            try std.testing.expectEqual(Pane.Mode.tty, pane.mode);
            try noChildInput(p);
            _ = try p.render(frame.allocator());
            try std.testing.expectEqualStrings(expected, pardes.test_api.heldSelection(p, 0).?);
            p.update(.{ .output = .{ .pane = 0, .bytes = "\x1b]133;C\x07" ++ "\r\nnew output" ** 30 } });
            _ = try p.render(frame.allocator());
            try std.testing.expectEqual(Pane.Mode.tty, pane.mode);
            try std.testing.expectEqualStrings(expected, pardes.test_api.heldSelection(p, 0).?);
            try std.testing.expectEqualStrings(expected, p.yank.?);
            try noChildInput(p);
        }
    }

    test "tty selection pastes across panes once with existing bracket and mouse protocols" {
        if (comptime !panes.Terminal.enabled) return error.SkipZigTest;
        for ([_]bool{ false, true }) |bracketed| {
            for ([_]bool{ false, true }) |reports_mouse| {
                const p = try Pardes.init(std.testing.allocator, .{ .tty_only = true, .cols = 40, .rows = 24 });
                defer p.deinit();
                p.presentation.enabled = false;
                p.spawnTty(0);
                for (p.panes[0..2]) |slot| {
                    slot.?.mode = .tty;
                    slot.?.tty_filter = false;
                    slot.?.greet = false;
                    slot.?.vweight = 1;
                }
                p.update(.tick);
                while (p.nextEffect()) |_| {}
                p.update(.{ .output = .{ .pane = 0, .bytes = "alpha\r\nbravo" } });
                p.update(.{ .output = .{ .pane = 1, .bytes = "target> " } });
                if (bracketed) p.update(.{ .output = .{ .pane = 1, .bytes = "\x1b[?2004h" } });
                if (reports_mouse) p.update(.{ .output = .{ .pane = 1, .bytes = "\x1b[?1000h\x1b[?1006h" } });
                var frame = std.heap.ArenaAllocator.init(p.gpa);
                defer frame.deinit();
                _ = try p.render(frame.allocator());
                const source = p.rects[0];
                const sx = source.x + config.GUTTER;
                const sy = if (p.settings.tag_bottom) source.y else source.y + pardes.BOX_H;
                JumpSelectionTests.drag(p, sx + 1, sy, sx + 3, sy + 1);
                try std.testing.expectEqualStrings("lph\nrav", p.yank orelse return error.MissingAutomaticTtyYank);
                try noChildInput(p);

                const target = p.rects[1];
                const tx = target.x + config.GUTTER + 2;
                const ty = if (p.settings.tag_bottom) target.y else target.y + pardes.BOX_H;
                p.update(.{ .mouse = .{ .button = .left, .kind = .press, .col = tx, .row = ty } });
                p.update(.{ .mouse = .{ .button = .right, .kind = .press, .col = tx, .row = ty } });
                p.update(.{ .mouse = .{ .button = .right, .kind = .release, .col = tx, .row = ty } });
                p.update(.{ .mouse = .{ .button = .left, .kind = .release, .col = tx, .row = ty } });
                var written: std.Io.Writer.Allocating = .init(p.gpa);
                defer written.deinit();
                while (p.nextEffect()) |effect| {
                    if (effect == .write) {
                        try std.testing.expectEqual(@as(u8, 1), effect.write.pane);
                        try written.writer.writeAll(effect.write.bytes.slice());
                    }
                }
                const expected = try std.fmt.allocPrint(p.gpa, "{s}{s}", .{
                    if (reports_mouse) "\x1b[<0;3;1M\x1b[<0;3;1m" else "",
                    if (bracketed) "\x1b[200~lph\nrav\x1b[201~" else "lph\rrav",
                });
                defer p.gpa.free(expected);
                try std.testing.expectEqualStrings(expected, written.written());
                try std.testing.expectEqual(Pane.Mode.tty, p.panes[0].?.mode);
                try std.testing.expectEqual(Pane.Mode.tty, p.panes[1].?.mode);
                try std.testing.expectEqualStrings("lph\nrav", pardes.test_api.heldSelection(p, 0).?);
            }
        }
    }
};

const ClickCursorTests = struct {
    fn click(p: *Pardes, button: pardes.Mouse.Button, x: u16, y: u16) void {
        p.update(.{ .mouse = .{ .button = button, .kind = .press, .col = x, .row = y } });
        p.update(.{ .mouse = .{ .button = button, .kind = .release, .col = x, .row = y } });
    }

    test "click cursor and insertion agree beyond line and file ends" {
        for ([_]bool{ false, true }) |already_insert| {
            for ([_]bool{ false, true }) |bottom_tag| {
                for ([_]struct { text: []const u8, click_row: u16, row: i32, col: i32, result: []const u8 }{
                    .{ .text = "abc\nxy", .click_row = 0, .row = 0, .col = 3, .result = "abcZ\nxy" },
                    .{ .text = "abc\nxy", .click_row = 5, .row = 1, .col = 2, .result = "abc\nxyZ" },
                    .{ .text = "abc\n", .click_row = 5, .row = 1, .col = 0, .result = "abc\nZ" },
                    .{ .text = "", .click_row = 5, .row = 0, .col = 0, .result = "Z" },
                }) |case| {
                    const p = try Pardes.init(std.testing.allocator, .{ .tty_only = true, .cols = 40, .rows = 12 });
                    defer p.deinit();
                    p.settings.tag_bottom = bottom_tag;
                    const pane = try p.setTestFile(case.text);
                    p.presentation.enabled = false;
                    if (already_insert) p.update(.{ .key = .{ .cp = 'i' } });
                    var frame = std.heap.ArenaAllocator.init(p.gpa);
                    defer frame.deinit();
                    _ = try p.render(frame.allocator());
                    const rect = p.rects[0];
                    const x = rect.x + config.GUTTER + panes.File.gutterWidth(pane);
                    const y = if (bottom_tag) rect.y else rect.y + pardes.BOX_H;
                    click(p, .left, x + 15, y + case.click_row);
                    try std.testing.expectEqual(case.row, pane.cur_row);
                    try std.testing.expectEqual(case.col, pane.cur_col);
                    const clicked = (try p.render(frame.allocator())).cursor orelse return error.MissingClickCursor;
                    try std.testing.expectEqual(x + @as(u16, @intCast(case.col)), clicked.x);
                    try std.testing.expectEqual(y + @as(u16, @intCast(case.row)), clicked.y);
                    if (!already_insert) p.update(.{ .key = .{ .cp = 'i' } });
                    try std.testing.expectEqual(Pane.Mode.insert, pane.mode);
                    const insert = (try p.render(frame.allocator())).cursor orelse return error.MissingInsertCursor;
                    try std.testing.expectEqual(clicked.x, insert.x);
                    try std.testing.expectEqual(clicked.y, insert.y);
                    p.update(.{ .key = .{ .cp = 'Z', .text = "Z" } });
                    try std.testing.expectEqualStrings(case.result, pane.file.?.content);
                }
            }
        }
    }

    test "click cursor snaps tab and wrapped wide glyph cells before insertion" {
        for ([_]bool{ false, true }) |already_insert| {
            for ([_]bool{ false, true }) |wrap| {
                const source = if (wrap) "012345678901234567890123456789界tail\n" else "\t界tail\n";
                const p = try Pardes.init(std.testing.allocator, .{ .tty_only = true, .cols = 24, .rows = 12 });
                defer p.deinit();
                const pane = try p.setTestFile(source);
                p.settings.wrap = wrap;
                p.presentation.enabled = false;
                if (already_insert) p.update(.{ .key = .{ .cp = 'i' } });
                var frame = std.heap.ArenaAllocator.init(p.gpa);
                defer frame.deinit();
                const surface = try p.render(frame.allocator());
                var target: ?struct { x: u16, y: u16 } = null;
                for (0..surface.rows) |row| for (0..surface.cols) |col| {
                    if (std.mem.eql(u8, surface.at(@intCast(col), @intCast(row)).grapheme(), "界"))
                        target = .{ .x = @intCast(col), .y = @intCast(row) };
                };
                const glyph = target orelse return error.MissingWideGlyph;
                if (wrap) try std.testing.expect(glyph.y > p.rects[0].y + pardes.BOX_H);
                click(p, .left, glyph.x + 1, glyph.y);
                const byte = std.mem.indexOf(u8, source, "界").?;
                try std.testing.expectEqual(@as(i32, @intCast(byte)), pane.cur_col);
                const clicked = (try p.render(frame.allocator())).cursor orelse return error.MissingClickCursor;
                try std.testing.expectEqual(glyph.x, clicked.x);
                try std.testing.expectEqual(glyph.y, clicked.y);
                if (!already_insert) p.update(.{ .key = .{ .cp = 'i' } });
                try std.testing.expectEqual(Pane.Mode.insert, pane.mode);
                const insert = (try p.render(frame.allocator())).cursor orelse return error.MissingInsertCursor;
                try std.testing.expectEqual(clicked.x, insert.x);
                try std.testing.expectEqual(clicked.y, insert.y);
                p.update(.{ .key = .{ .cp = 'Z', .text = "Z" } });
                const expected = try std.fmt.allocPrint(p.gpa, "{s}Z{s}", .{ source[0..byte], source[byte..] });
                defer p.gpa.free(expected);
                try std.testing.expectEqualStrings(expected, pane.file.?.content);
            }
        }
    }

    test "click operands and hover follow the scrolled source selection" {
        const p = try Pardes.init(std.testing.allocator, .{ .tty_only = true, .cols = 40, .rows = 14 });
        defer p.deinit();
        const pane = try p.setTestFile("zero\none\ntwo\nthree\nalpha beta\nfive\ngamma delta\nseven\n" ++ "tail\n" ** 20);
        p.presentation.enabled = false;
        p.settings.wrap = false;
        var frame = std.heap.ArenaAllocator.init(p.gpa);
        defer frame.deinit();
        _ = try p.render(frame.allocator());
        const rect = p.rects[0];
        const x = rect.x + config.GUTTER + panes.File.gutterWidth(pane);
        const y = if (p.settings.tag_bottom) rect.y else rect.y + pardes.BOX_H;
        JumpSelectionTests.drag(p, x + 1, y + 4, x + 3, y + 4);
        try std.testing.expectEqualStrings("lph", pardes.test_api.heldSelection(p, 0).?);
        for (0..2) |_| p.update(.{ .mouse = .{ .button = .wheel_down, .kind = .press, .col = x + 2, .row = y + 4 } });
        try std.testing.expectEqual(@as(usize, 2), pane.file.?.scroll);
        _ = try p.render(frame.allocator());
        const event_node = filesystem.Node.of(pane.serial, .event);
        const opened = filesystem.handle(p, .{ .tag = 0, .op = .open, .node = event_node });
        try std.testing.expectEqual(.ok, opened.status);
        defer _ = filesystem.handle(p, .{ .tag = 0, .op = .release, .node = event_node, .handle = opened.handle });

        for ([_]pardes.Mouse.Button{ .middle, .right }) |button| {
            const events = &p.fs.panes[0].events;
            while (!events.empty()) events.pop();
            click(p, button, x + 2, y + 2);
            const selected = events.peek() orelse return error.MissingSelectionGesture;
            try std.testing.expect(std.mem.endsWith(u8, selected, " lph\n"));
            try std.testing.expect(std.mem.startsWith(u8, selected[2..], "20 23 "));
            while (!events.empty()) events.pop();
            click(p, button, x + 2, y + 4);
            const unselected = events.peek() orelse return error.MissingWordGesture;
            try std.testing.expect(std.mem.endsWith(u8, unselected, " gamma\n"));
        }

        const delay = config.look_preview_delay_frames orelse return;
        p.update(.{ .mouse = .{ .button = .none, .kind = .motion, .col = x + 2, .row = y + 2 } });
        for (0..delay) |_| p.update(.tick);
        const selected_preview = p.look_hover_preview orelse return error.MissingSelectionHover;
        try std.testing.expect(selected_preview.sel != null);
        try std.testing.expect(pane.pointerSelection(selected_preview.sel.?) != null);
        p.update(.{ .mouse = .{ .button = .none, .kind = .motion, .col = x + 2, .row = y + 4 } });
        for (0..delay) |_| p.update(.tick);
        const word_preview = p.look_hover_preview orelse return error.MissingWordHover;
        try std.testing.expect(word_preview.file_word != null);
        try std.testing.expectEqual(@as(i32, 6), word_preview.file_word.?.row);
    }
};

const JumpSelectionTests = struct {
    fn drag(p: *Pardes, col0: u16, row0: u16, col1: u16, row1: u16) void {
        p.update(.{ .mouse = .{ .button = .left, .kind = .press, .col = col0, .row = row0 } });
        p.update(.{ .mouse = .{ .button = .left, .kind = .drag, .col = col1, .row = row1 } });
        p.update(.{ .mouse = .{ .button = .left, .kind = .release, .col = col1, .row = row1 } });
    }

    fn exercise(prefix: []const u8, wrap: bool, reverse: bool, first_col: u16, last_col: u16, expected: ?[]const u8) !void {
        const p = try Pardes.init(std.testing.allocator, .{ .tty_only = true, .cols = 34, .rows = 10 });
        defer p.deinit();
        p.settings.wrap = wrap;
        const text = try std.fmt.allocPrint(p.gpa, "{s}{s}", .{ prefix, "unrelated destination text\n" ** 80 });
        defer p.gpa.free(text);
        const pane = try p.setTestFile(text);
        var frame = std.heap.ArenaAllocator.init(p.gpa);
        defer frame.deinit();
        _ = try p.render(frame.allocator());
        if (wrap) try std.testing.expectEqual(pane.wrap_line[0], pane.wrap_line[1]);
        const rect = p.rects[0];
        const x = rect.x + config.GUTTER + panes.File.gutterWidth(pane);
        const y = if (p.settings.tag_bottom) rect.y else rect.y + pardes.BOX_H;
        if (reverse)
            drag(p, x + last_col, y + 1, x + first_col, y)
        else
            drag(p, x + first_col, y, x + last_col, y + 1);

        const selected = try p.gpa.dupe(u8, pardes.test_api.heldSelection(p, 0) orelse return error.MissingMouseSelection);
        defer p.gpa.free(selected);
        if (expected) |want| try std.testing.expectEqualStrings(want, selected);
        try std.testing.expect(std.mem.indexOfScalar(u8, selected, '\n') != null);
        if (wrap) try std.testing.expect(std.mem.indexOf(u8, selected, "界") != null);

        // Seed two actual locations after the drag, so both history directions
        // must scroll while retaining the rectangle's original source text.
        p.njumps = 2;
        p.jcur = 1;
        p.jumps[0] = .{ .pane = 0, .serial = pane.serial, .line = 60, .col = 1 };
        p.jumps[1] = .{ .pane = 0, .serial = pane.serial, .line = 1, .col = 1 };
        p.update(.{ .key = .{ .cp = 'o', .ctrl = true } });
        _ = frame.reset(.retain_capacity);
        _ = try p.render(frame.allocator());
        try std.testing.expectEqual(@as(usize, 0), p.jcur);
        try std.testing.expect(pane.file.?.scroll > 20);
        try std.testing.expectEqualStrings(selected, pardes.test_api.heldSelection(p, 0) orelse return error.LostMouseSelection);

        p.update(.{ .key = .{ .cp = 'i', .ctrl = true } });
        _ = frame.reset(.retain_capacity);
        _ = try p.render(frame.allocator());
        try std.testing.expectEqual(@as(usize, 1), p.jcur);
        try std.testing.expectEqual(@as(usize, 0), pane.file.?.scroll);
        try std.testing.expectEqualStrings(selected, pardes.test_api.heldSelection(p, 0) orelse return error.LostMouseSelection);
    }

    test "jump selection retains copied rectangle text after scrolling away and back" {
        for ([_]bool{ false, true }) |reverse|
            try exercise("alpha\nbravo\n", false, reverse, 1, 3, "lph\nrav");
    }

    test "jump selection retains wrapped Unicode and tab rectangle text" {
        for ([_]bool{ false, true }) |reverse|
            try exercise("界\tabcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789\n", true, reverse, 0, 8, null);
    }
};

const TagNameTintTests = struct {
    const name_fg = [3]u8{ 231, 137, 43 };
    const tag_fg = [3]u8{ 111, 122, 133 };

    fn configure(p: *Pardes) void {
        var theme = p.theme().*;
        theme.tag_name_fg = name_fg;
        theme.tag_fg = tag_fg;
        p.custom_theme = theme;
        p.chrome_animation.snap(pardes.ChromeTheme.fromTheme(p.theme()));
        p.settings.focus_tint = false;
        p.presentation.enabled = false;
    }

    fn check(p: *Pardes, id: usize, name: []const u8) !usize {
        const pane = p.panes[id].?;
        var arena = std.heap.ArenaAllocator.init(p.gpa);
        defer arena.deinit();
        const surface = try p.render(arena.allocator());
        const text = try p.tagText(arena.allocator(), pane);
        const base = std.mem.lastIndexOfScalar(u8, name, '/') orelse return error.MissingDirectory;
        const rect = p.rects[id];
        const y = if (p.settings.tag_bottom) rect.y + rect.h - pardes.BOX_H else rect.y;
        const left = rect.x + config.GUTTER;
        var visible_name: usize = 0;
        var at: usize = 0;
        while (at < text.len) : (at = modal.nextGrapheme(text, at)) {
            const start: i32 = @as(i32, @intCast(panes.File.rawDisplayCol(text, at))) - pane.tag_scroll;
            const end = start + @as(i32, @intCast(panes.File.displayWidth(text[at..modal.nextGrapheme(text, at)])));
            var col = @max(0, start);
            while (col < end and col < rect.w - config.GUTTER) : (col += 1) {
                const in_name = at > base and at < name.len;
                const fg = if (in_name) name_fg else tag_fg;
                try std.testing.expectEqual(pardes.Color{ .rgb = fg }, surface.at(left + @as(u16, @intCast(col)), y).style.fg);
                if (in_name) visible_name += 1;
            }
        }
        return visible_name;
    }

    test "tag filename tint excludes directories dirty marker and output commands" {
        for ([_]bool{ false, true }) |bottom| {
            const p = try Pardes.init(std.testing.allocator, .{ .tty_only = true, .cols = 100, .rows = 24 });
            defer p.deinit();
            const pane = try p.setTestFile("body\n");
            p.gpa.free(pane.file.?.path);
            pane.file.?.path = try p.gpa.dupe(u8, "/project/界file.zig");
            pane.file.?.revision += 1;
            configure(p);
            defer p.custom_theme = null;
            p.settings.tag_bottom = bottom;
            try std.testing.expect((try check(p, 0, pane.file.?.path)) > 0);
            try panes.Output.fillResults(p, 0, "/project", .search, "tint", try p.gpa.dupe(u8, "no matches\n"), null);
            const id = pane.search_pane.?;
            p.update(.tick);
            try std.testing.expect((try check(p, id, p.panes[id].?.file.?.path)) > 0);
        }
    }

    test "tag filename tint follows scrolled Unicode staged names and yields to selection" {
        const p = try Pardes.init(std.testing.allocator, .{ .tty_only = true, .cols = 38, .rows = 14 });
        defer p.deinit();
        const pane = try p.setTestFile("body\n");
        const old = pane.file.?.path.len;
        configure(p);
        defer p.custom_theme = null;
        p.update(.{ .key = .{ .cp = ':' } });
        p.update(.{ .key = .{ .cp = 'i' } });
        pane.tag_anchor = 0;
        pane.tag_col = @intCast(old - 1);
        pane.tag_sel = true;
        const name = "/a/very/long/directory/that/extends/past/the/tag/界e\u{301}name-with-a-long-tail.zig";
        p.update(.{ .paste = name });
        try std.testing.expectEqualStrings(name, pane.tag_name[0..pane.tag_name_len.?]);
        pane.tag_col = @intCast(std.mem.indexOf(u8, name, "界").?);
        pane.tag_sel = false;
        try std.testing.expect((try check(p, 0, name)) > 0);
        try std.testing.expect(pane.tag_scroll > 0);
        pane.tag_anchor = pane.tag_col;
        pane.tag_sel = true;
        pane.tag_scroll += 4; // bring both cells of the selected wide glyph into view
        var arena = std.heap.ArenaAllocator.init(p.gpa);
        defer arena.deinit();
        const surface = try p.render(arena.allocator());
        const x = p.rects[0].x + config.GUTTER + @as(u16, @intCast(panes.File.rawDisplayCol(name, pane.tag_col) - pane.tag_scroll));
        const y = if (p.settings.tag_bottom) p.rects[0].y + p.rects[0].h - pardes.BOX_H else p.rects[0].y;
        try std.testing.expectEqual(pardes.Color{ .rgb = p.theme().sel_fg }, surface.at(x, y).style.fg);
        try std.testing.expectEqual(pardes.Color{ .rgb = p.theme().sel_fg }, surface.at(x + 1, y).style.fg);
    }

    test "tag filename tint legacy themes retain distinct active foreground" {
        const p = try Pardes.init(std.testing.allocator, .{ .tty_only = true, .cols = 70, .rows = 14 });
        defer p.deinit();
        const pane = try p.setTestFile("body\n");
        p.gpa.free(pane.file.?.path);
        pane.file.?.path = try p.gpa.dupe(u8, "/dir/file.zig");
        configure(p);
        defer p.custom_theme = null;
        p.custom_theme.?.tag_name_fg = null;
        const active_fg = [3]u8{ 175, 183, 194 };
        p.custom_theme.?.tag_active_fg = active_fg;
        p.chrome_animation.snap(pardes.ChromeTheme.fromTheme(p.theme()));
        var arena = std.heap.ArenaAllocator.init(p.gpa);
        defer arena.deinit();
        for ([_]bool{ false, true }) |active| {
            p.settings.focus_tint = active;
            const surface = try p.render(arena.allocator());
            const x = p.rects[0].x + config.GUTTER;
            const y = if (p.settings.tag_bottom) p.rects[0].y + p.rects[0].h - pardes.BOX_H else p.rects[0].y;
            const fg = if (active) active_fg else tag_fg;
            try std.testing.expectEqual(pardes.Color{ .rgb = fg }, surface.at(x + 1, y).style.fg);
            try std.testing.expectEqual(pardes.Color{ .rgb = fg }, surface.at(x + 5, y).style.fg);
        }
    }
};

test "pane filename edits stage commit and cancel without changing body or command tail" {
    const p = try Pardes.init(std.testing.allocator, .{ .tty_only = true, .cols = 70, .rows = 12 });
    defer p.deinit();
    const pane = try p.setTestFile("original body\n");
    const original = try p.gpa.dupe(u8, pane.file.?.path);
    defer p.gpa.free(original);
    p.seedTail(pane);
    try std.testing.expect(pane.appendTag(" SyntaxBold"));
    const tail = try p.gpa.dupe(u8, pane.tagSlice());
    defer p.gpa.free(tail);
    for ([_]bool{ false, true }) |commit| {
        p.update(.{ .key = .{ .cp = ':' } });
        p.update(.{ .key = .{ .cp = 'i' } });
        pane.tag_anchor = 0;
        pane.tag_col = @intCast(original.len - 1);
        pane.tag_sel = true;
        p.update(.{ .paste = "/new name.zig" });
        try std.testing.expectEqualStrings(original, pane.file.?.path);
        try std.testing.expectEqualStrings("/new name.zig", pane.tag_name[0..pane.tag_name_len.?]);
        try std.testing.expectEqualStrings(tail, pane.tagSlice());
        try std.testing.expectEqualStrings("original body\n", pane.file.?.content);
        p.update(.{ .key = .{ .cp = if (commit) Key.enter else Key.escape } });
        try std.testing.expect(!pane.tag_edit);
        try std.testing.expect(pane.tag_name_len == null);
        try std.testing.expectEqualStrings(if (commit) "/new name.zig" else original, pane.file.?.path);
        try std.testing.expectEqualStrings(tail, pane.tagSlice());
        while (p.nextEffect()) |effect| try std.testing.expect(std.meta.activeTag(effect) != .save_file);
    }
    try std.testing.expect(pane.file.?.revision != pane.file.?.saved_revision);
}

test "pane filename grapheme edits and invalid empty commits preserve the buffer" {
    const p = try Pardes.init(std.testing.allocator, .{ .tty_only = true });
    defer p.deinit();
    const pane = try p.setTestFile("untouched\n");
    p.update(.{ .key = .{ .cp = ':' } });
    p.update(.{ .key = .{ .cp = 'i' } });
    pane.tag_anchor = 0;
    pane.tag_col = @intCast(pane.file.?.path.len - 1);
    pane.tag_sel = true;
    p.update(.{ .paste = "/café界" });
    p.update(.{ .key = .{ .cp = Key.backspace } });
    try std.testing.expectEqualStrings("/café", pane.tag_name[0..pane.tag_name_len.?]);
    p.update(.{ .key = .{ .cp = Key.backspace } });
    try std.testing.expectEqualStrings("/caf", pane.tag_name[0..pane.tag_name_len.?]);
    pane.tag_anchor = 0;
    pane.tag_col = 3;
    pane.tag_sel = true;
    p.update(.{ .key = .{ .cp = Key.delete } });
    try std.testing.expectEqual(@as(u16, 0), pane.tag_name_len.?);
    p.update(.{ .key = .{ .cp = Key.enter } });
    try std.testing.expect(pane.tag_edit);
    try std.testing.expectEqualStrings("/test.txt", pane.file.?.path);
    try std.testing.expectEqualStrings("untouched\n", pane.file.?.content);
    p.update(.{ .key = .{ .cp = Key.escape } });
    try std.testing.expect(pane.tag_name_len == null);
}

test "leaving a pane or entering a header cancels an uncommitted filename" {
    const p = try Pardes.init(std.testing.allocator, .{ .tty_only = true });
    defer p.deinit();
    const pane = try p.setTestFile("untouched\n");
    for ([_]bool{ false, true }) |header| {
        p.active = 0;
        p.topbar_col = null;
        p.update(.{ .key = .{ .cp = ':' } });
        p.update(.{ .key = .{ .cp = 'i' } });
        p.update(.{ .key = .{ .cp = Key.home } });
        p.update(.{ .paste = "/draft" });
        try std.testing.expect(pane.tag_name_len != null);
        if (header) {
            p.topbar_col = 0;
            p.update(.tick);
        } else {
            try std.testing.expect(p.executeBuiltinLine(0, "New"));
            p.update(.tick);
        }
        try std.testing.expect(pane.tag_name_len == null);
        try std.testing.expect(!pane.tag_edit);
        try std.testing.expectEqualStrings("/test.txt", pane.file.?.path);
    }
}

test "middle clicking Save commits the staged filename before issuing a save" {
    const p = try Pardes.init(std.testing.allocator, .{ .tty_only = true, .cols = 70, .rows = 12 });
    defer p.deinit();
    const pane = try p.setTestFile("untouched\n");
    p.update(.{ .key = .{ .cp = ':' } });
    p.update(.{ .key = .{ .cp = 'i' } });
    pane.tag_anchor = 0;
    pane.tag_col = @intCast(pane.file.?.path.len - 1);
    pane.tag_sel = true;
    p.update(.{ .paste = "/renamed.txt" });
    var arena = std.heap.ArenaAllocator.init(p.gpa);
    defer arena.deinit();
    _ = try p.render(arena.allocator());
    const text = try p.tagText(arena.allocator(), pane);
    const save_at = std.mem.indexOf(u8, text, "Save").?;
    const x: u16 = @intCast(p.rects[0].x + config.GUTTER + save_at - pane.tag_scroll);
    const y = p.rects[0].y;
    while (p.nextEffect()) |_| {}
    p.update(.{ .mouse = .{ .col = x, .row = y, .button = config.exec_button, .kind = .press } });
    p.update(.{ .mouse = .{ .col = x, .row = y, .button = config.exec_button, .kind = .release } });
    try std.testing.expectEqualStrings("/renamed.txt", pane.file.?.path);
    try std.testing.expect(pane.tag_name_len == null);
    try std.testing.expectEqualStrings("untouched\n", pane.file.?.content);
    var saves: usize = 0;
    while (p.nextEffect()) |effect| if (effect == .save_file) {
        try std.testing.expectEqual(@as(u8, 0), effect.save_file.pane);
        saves += 1;
    };
    try std.testing.expectEqual(@as(usize, 1), saves);
}

test "oversized filename paste refuses atomically across a selected tag boundary" {
    const p = try Pardes.init(std.testing.allocator, .{ .tty_only = true });
    defer p.deinit();
    const pane = try p.setTestFile("untouched\n");
    p.update(.{ .key = .{ .cp = ':' } });
    p.update(.{ .key = .{ .cp = 'i' } });
    const before = try p.tagText(p.gpa, pane);
    defer p.gpa.free(before);
    pane.tag_anchor = 0;
    pane.tag_col = @intCast(before.len - 1);
    pane.tag_sel = true;
    const excess = try p.gpa.alloc(u8, pane.tag_name.len + 1);
    defer p.gpa.free(excess);
    @memset(excess, 'x');
    p.update(.{ .paste = excess });
    try std.testing.expect(pane.tag_name_len == null);
    try std.testing.expect(pane.tag_sel);
    try std.testing.expectEqualStrings(before, try p.tagText(p.scratch.allocator(), pane));
    try std.testing.expectEqualStrings("untouched\n", pane.file.?.content);
}

test "paste into pane commands and prompts never inserts into the body" {
    const p = try Pardes.init(std.testing.allocator, .{ .tty_only = true });
    defer p.deinit();
    const pane = try p.setTestFile("one two one\n");
    p.update(.{ .key = .{ .cp = ':' } });
    p.update(.{ .key = .{ .cp = 'A' } });
    p.update(.{ .paste = " Custom\r\nCommand" });
    try std.testing.expect(std.mem.endsWith(u8, pane.tagSlice(), " CustomCommand"));
    p.update(.{ .key = .{ .cp = Key.escape } });
    p.startPrompt(pane, .{ .search = config.search_marker });
    p.update(.{ .paste = "two" });
    try std.testing.expect(std.mem.endsWith(u8, pane.tagSlice(), "two"));
    try std.testing.expectEqualStrings("one two one\n", pane.file.?.content);
    p.update(.{ .key = .{ .cp = Key.escape } });
    try std.testing.expect(std.mem.endsWith(u8, pane.tagSlice(), " CustomCommand"));
}

test "long pane tags reveal commands and map visible clicks to whole tag addresses" {
    const p = try Pardes.init(std.testing.allocator, .{ .tty_only = true, .cols = 50, .rows = 12 });
    defer p.deinit();
    const pane = try p.setTestFile("body\n");
    p.gpa.free(pane.file.?.path);
    pane.file.?.path = try p.gpa.dupe(u8, "/an/especially/deep/project/path/with/a/long/component/filename.zig");
    p.seedTail(pane);
    try std.testing.expect(pane.appendTag(" SyntaxBold"));
    p.update(.{ .key = .{ .cp = ':' } });
    p.update(.{ .key = .{ .cp = 'A' } });
    var arena = std.heap.ArenaAllocator.init(p.gpa);
    defer arena.deinit();
    const surface = try p.render(arena.allocator());
    try std.testing.expect(pane.tag_scroll > 0);
    try std.testing.expect(surface.cursor.?.x < p.rects[0].x + p.rects[0].w);
    const text = try p.tagText(p.gpa, pane);
    defer p.gpa.free(text);
    const offset = std.mem.indexOf(u8, text, "SyntaxBold").?;
    const x: u16 = @intCast(p.rects[0].x + config.GUTTER + panes.File.rawDisplayCol(text, offset) - pane.tag_scroll);
    const y = p.rects[0].y;
    const before = p.settings.syntax_bold;
    p.update(.{ .mouse = .{ .col = x, .row = y, .button = config.exec_button, .kind = .press } });
    p.update(.{ .mouse = .{ .col = x, .row = y, .button = config.exec_button, .kind = .release } });
    try std.testing.expectEqual(!before, p.settings.syntax_bold);
    try std.testing.expectEqualStrings(text, try p.tagText(p.scratch.allocator(), pane));
}

test "terminal overlay recoloring never materializes unrelated history" {
    const testing = std.testing;
    const p = try Pardes.init(testing.allocator, .{ .tty_only = true, .cols = 32, .rows = 8 });
    defer p.deinit();
    while (p.nextEffect()) |_| {}
    const pane = p.panes[0].?;
    pane.tty_filter = false;
    for (0..1000) |_| p.update(.{ .output = .{ .pane = 0, .bytes = "\x1b[32mcaf\xc3\xa9 \xe7\x95\x8c\x1b[0m\r\n" } });
    pane.mode = .normal;
    pane.ovl = .{ .row = 0, .rows = 1, .text = try p.gpa.dupe(u8, "edited history") };
    var frame = std.heap.ArenaAllocator.init(testing.allocator);
    defer frame.deinit();
    _ = try p.render(frame.allocator());
    try testing.expect(p.shell_rows.pane == null);

    pane.ovl.?.row = panes.Terminal.gridOffset(pane);
    p.gpa.free(pane.ovl.?.text);
    pane.ovl.?.text = try p.gpa.dupe(u8, "caf\xc3\xa9 \xe7\x95\x8c");
    _ = frame.reset(.retain_capacity);
    const surface = try p.render(frame.allocator());
    try testing.expect(p.shell_rows.pane == null);
    const rect = p.rects[0];
    const body_y = if (p.settings.tag_bottom) rect.y else rect.y + pardes.BOX_H;
    const cell = surface.at(rect.x + config.GUTTER, body_y);
    try testing.expectEqualStrings("c", cell.grapheme());
    try testing.expectEqual(pardes.Color{ .rgb = p.theme().palette.?[2] }, cell.style.fg);
}

test "terminal output keeps following new rows after scrollback eviction" {
    if (comptime !panes.Terminal.enabled) return error.SkipZigTest;
    const gpa = std.testing.allocator;
    const p = try Pardes.init(gpa, .{ .tty_only = true, .cols = 80, .rows = 24 });
    defer p.deinit();
    while (p.nextEffect()) |_| {}
    const pane = p.panes[0].?;
    pane.mode = .tty;
    pane.tty_filter = false;
    const pages = &pane.terminal.?.vt.screens.active.pages;
    pages.explicit_max_size = 64 * 1024;
    var frame = std.heap.ArenaAllocator.init(gpa);
    defer frame.deinit();
    var evictions: usize = 0;
    for (0..3) |phase| {
        if (phase > 0) {
            pane.mode = .normal;
            panes.Terminal.scrollGrid(pane, -30);
            try std.testing.expect(pages.scrollbar().offset < pages.scrollbar().total - pane.rows);
            panes.Terminal.enterTty(p, 0);
        }
        for (phase * 20_000..(phase + 1) * 20_000) |n| {
            var buf: [64]u8 = undefined;
            const bytes = try std.fmt.bufPrint(&buf, "\x1b[32mrow-{d:0>5}\x1b[0m\r\n", .{n});
            const previous = pages.scrollbar().total;
            p.update(.{ .output = .{ .pane = 0, .bytes = bytes } });
            if (pages.scrollbar().total < previous) evictions += 1;
        }
        try std.testing.expect(evictions > phase);
        try std.testing.expect(pages.page_size <= pages.maxSize());
        const sb = pages.scrollbar();
        try std.testing.expectEqual(sb.total - pane.rows, sb.offset);
        const full = try panes.Terminal.screenTextAlloc(pane, gpa);
        defer gpa.free(full);
        var last_buf: [16]u8 = undefined;
        const last = try std.fmt.bufPrint(&last_buf, "row-{d:0>5}", .{(phase + 1) * 20_000 - 1});
        try std.testing.expect(std.mem.indexOf(u8, full, "row-00000") == null);
        try std.testing.expect(std.mem.endsWith(u8, std.mem.trimEnd(u8, full, "\n"), last));
        _ = frame.reset(.retain_capacity);
        const surface = try p.render(frame.allocator());
        const rect = p.rects[0];
        const x = rect.x + config.GUTTER;
        const y = (if (p.settings.tag_bottom) rect.y else rect.y + pardes.BOX_H) + pane.rows - 2;
        for (last, 0..) |byte, col| {
            const cell = surface.at(x + @as(u16, @intCast(col)), y);
            try std.testing.expectEqualStrings(&.{byte}, cell.grapheme());
            try std.testing.expectEqual(pardes.Color{ .rgb = p.theme().palette.?[2] }, cell.style.fg);
        }
        while (p.nextEffect()) |_| {}
        p.update(.{ .key = .{ .cp = 'f', .text = "f" } });
        const effect = p.nextEffect() orelse return error.MissingTerminalInput;
        try std.testing.expectEqual(.write, std.meta.activeTag(effect));
        try std.testing.expectEqual(@as(u8, 0), effect.write.pane);
        try std.testing.expectEqualStrings("f", effect.write.bytes.slice());
        try std.testing.expect(p.nextEffect() == null);
    }
    const replay = &pane.terminal.?.replay;
    try std.testing.expectEqual(replay.bytes.len, replay.len);
    try std.testing.expect(replay.head > 0);
}

test "terminal edit stays on its surviving row when old scrollback is evicted" {
    if (comptime !panes.Terminal.enabled) return error.SkipZigTest;
    const gpa = std.testing.allocator;
    const p = try Pardes.init(gpa, .{ .tty_only = true, .cols = 80, .rows = 24 });
    defer p.deinit();
    while (p.nextEffect()) |_| {}
    const pane = p.panes[0].?;
    pane.mode = .tty;
    const pages = &pane.terminal.?.vt.screens.active.pages;
    pages.explicit_max_size = 64 * 1024;
    var next: usize = 0;
    while (next < 3000) {
        var buf: [32]u8 = undefined;
        const bytes = try std.fmt.bufPrint(&buf, "row-{d:0>5}\r\n", .{next});
        p.update(.{ .output = .{ .pane = 0, .bytes = bytes } });
        next += 1;
        if (pages.scrollbar().total > pages.pages.first.?.rows() + pane.rows + 10) break;
    }
    try std.testing.expect(next < 3000);
    var last_buf: [16]u8 = undefined;
    const last = try std.fmt.bufPrint(&last_buf, "row-{d:0>5}", .{next - 1});
    pane.mode = .normal;
    const original_row: i32 = @intCast(pages.scrollbar().total - 2);
    pane.ovl = .{ .row = original_row, .rows = 1, .text = try gpa.dupe(u8, "my unsent edit") };
    pane.cur_row = original_row;
    pane.cur_col = 3;
    pane.cur_pinned = true;
    var removed: usize = 0;
    for (next..next + 3000) |n| {
        var buf: [32]u8 = undefined;
        const bytes = try std.fmt.bufPrint(&buf, "row-{d:0>5}\r\n", .{n});
        const previous = pages.scrollbar().total;
        p.update(.{ .output = .{ .pane = 0, .bytes = bytes } });
        if (pages.scrollbar().total < previous) {
            removed = previous + 1 - pages.scrollbar().total;
            break;
        }
    }
    try std.testing.expect(removed > 0 and removed < original_row);
    const full = try panes.Terminal.screenTextAlloc(pane, gpa);
    defer gpa.free(full);
    const row = original_row - @as(i32, @intCast(removed));
    try std.testing.expectEqualStrings(last, modal.lineSlice(full, @intCast(row)));
    try std.testing.expectEqual(row, pane.ovl.?.row);
    try std.testing.expectEqual(row, pane.cur_row);
    try std.testing.expectEqualStrings("my unsent edit", pane.ovl.?.text);
}

test "terminal edits and undo survive partial history clearing and whole-screen loss" {
    if (comptime !panes.Terminal.enabled) return error.SkipZigTest;
    const gpa = std.testing.allocator;
    const Action = enum { clear_history, partial_clear_history, reset_primary, reset_alternate, evict_all, hidden_undo };
    for (std.enums.values(Action)) |action| {
        const p = try Pardes.init(gpa, .{ .tty_only = true, .cols = 80, .rows = 24 });
        defer p.deinit();
        while (p.nextEffect()) |_| {}
        const pane = p.panes[0].?;
        pane.mode = .tty;
        if (action == .reset_alternate)
            p.update(.{ .output = .{ .pane = 0, .bytes = "\x1b[?1049h" } });
        p.update(.{ .output = .{ .pane = 0, .bytes = "old row\r\n" ** 40 } });
        const pages = &pane.terminal.?.vt.screens.active.pages;
        pages.explicit_max_size = 64 * 1024;
        const row: i32 = @as(i32, @intCast(pages.total_rows - pane.rows)) +
            @as(i32, if (action == .partial_clear_history) -1 else 2);
        pane.mode = .normal;
        pane.ovl = .{ .row = row, .rows = if (action == .partial_clear_history) 3 else 2, .text = try gpa.dupe(u8, "edit one\nedit two") };
        pane.cur_row = row + 1;
        pane.cur_col = 4;
        pane.cur_pinned = true;
        pane.vsel = .{ .active = true, .row = row, .col = 1 };
        panes.Terminal.pushUndo(p, pane);
        pane.ed_redo[0] = panes.Terminal.snap(p, pane) orelse return error.SnapshotFailed;
        pane.ed_redo_len = 1;
        if (action == .hidden_undo) {
            gpa.free(pane.ovl.?.text);
            pane.ovl = null;
            panes.Terminal.enterTty(p, 0);
        }
        const bytes = switch (action) {
            .clear_history, .partial_clear_history => "\x1b[3J",
            .reset_primary, .reset_alternate => "\x1bc",
            .evict_all, .hidden_undo => "new row\r\n" ** 4000,
        };
        p.update(.{ .output = .{ .pane = 0, .bytes = bytes } });
        const expected: i32 = if (action == .clear_history) 2 else 0;
        if (pane.ovl) |edit| {
            try std.testing.expectEqual(expected, edit.row);
            try std.testing.expectEqual(@as(i32, if (action == .clear_history or action == .partial_clear_history) 2 else 1), edit.rows);
            try std.testing.expectEqualStrings("edit one\nedit two", edit.text);
            try std.testing.expectEqual(expected + 1, pane.cur_row);
            try std.testing.expectEqual(expected, pane.vsel.row);
        }
        for ([_]panes.Terminal.Snapshot{ pane.ed_undo[0], pane.ed_redo[0] }) |snapshot| {
            try std.testing.expectEqual(expected, snapshot.ovl.?.row);
            try std.testing.expectEqual(expected + 1, snapshot.cur_row);
            try std.testing.expectEqualStrings("edit one\nedit two", snapshot.ovl.?.text);
        }
        try std.testing.expectEqual(@as(usize, 2), pane.terminal.?.vt.screens.active.pages.countTrackedPins());
        panes.Terminal.undo(p, pane);
        try std.testing.expectEqualStrings("edit one\nedit two", pane.ovl.?.text);
        try std.testing.expectEqual(expected, pane.ovl.?.row);
    }
}

test "terminal lower scroll regions do not move edits above them" {
    if (comptime !panes.Terminal.enabled) return error.SkipZigTest;
    const gpa = std.testing.allocator;
    const p = try Pardes.init(gpa, .{ .tty_only = true, .cols = 80, .rows = 24 });
    defer p.deinit();
    while (p.nextEffect()) |_| {}
    const pane = p.panes[0].?;
    pane.mode = .normal;
    p.update(.{ .output = .{ .pane = 0, .bytes = "top\r\nsecond\r\nthird" } });
    pane.ovl = .{ .row = 1, .rows = 1, .text = try gpa.dupe(u8, "unsent") };
    pane.cur_row = 1;
    pane.cur_pinned = true;
    panes.Terminal.pushUndo(p, pane);
    const total = panes.Terminal.scrollbar(pane).total;
    var setup: [64]u8 = undefined;
    const bytes = try std.fmt.bufPrint(&setup, "\x1b[4;{d}r\x1b[{d};1H", .{ pane.rows, pane.rows });
    p.update(.{ .output = .{ .pane = 0, .bytes = bytes } });
    p.update(.{ .output = .{ .pane = 0, .bytes = "tail\r\n" ** 50 } });
    try std.testing.expectEqual(total, panes.Terminal.scrollbar(pane).total);
    try std.testing.expectEqual(@as(i32, 1), pane.ovl.?.row);
    try std.testing.expectEqual(@as(i32, 1), pane.cur_row);
    try std.testing.expectEqual(@as(i32, 1), pane.ed_undo[0].ovl.?.row);
    const full = try panes.Terminal.screenTextAlloc(pane, gpa);
    defer gpa.free(full);
    try std.testing.expect(std.mem.startsWith(u8, full, "top\nsecond\nthird\n"));
}

test "terminal eviction and lower-region scrolling in one read preserve a surviving edit" {
    if (comptime !panes.Terminal.enabled) return error.SkipZigTest;
    const gpa = std.testing.allocator;
    const p = try Pardes.init(gpa, .{ .tty_only = true, .cols = 80, .rows = 24 });
    defer p.deinit();
    while (p.nextEffect()) |_| {}
    const pane = p.panes[0].?;
    pane.mode = .tty;
    const pages = &pane.terminal.?.vt.screens.active.pages;
    pages.explicit_max_size = 64 * 1024;
    var next: usize = 0;
    while (next < 3000) {
        var buf: [32]u8 = undefined;
        const bytes = try std.fmt.bufPrint(&buf, "row-{d:0>5}\r\n", .{next});
        p.update(.{ .output = .{ .pane = 0, .bytes = bytes } });
        next += 1;
        if (pages.pages.first != pages.pages.last and
            pages.pages.last.?.rows() == pages.pages.last.?.capacity().rows) break;
    }
    try std.testing.expect(next < 3000);
    const removed = pages.pages.first.?.rows();
    const old_row: i32 = @intCast(removed + 2);
    pane.mode = .normal;
    pane.ovl = .{ .row = old_row, .rows = 1, .text = try gpa.dupe(u8, "kept edit") };
    pane.cur_row = old_row;
    pane.cur_pinned = true;
    panes.Terminal.pushUndo(p, pane);
    const old_total = pages.total_rows;
    var buf: [128]u8 = undefined;
    const bytes = try std.fmt.bufPrint(&buf, "new\r\n\x1b[4;{d}r\x1b[{d};1Hregion\r\n", .{ pane.rows, pane.rows });
    p.update(.{ .output = .{ .pane = 0, .bytes = bytes } });
    try std.testing.expectEqual(old_total + 1 - removed, pages.total_rows);
    try std.testing.expectEqual(@as(i32, 2), pane.ovl.?.row);
    try std.testing.expectEqual(@as(i32, 2), pane.cur_row);
    try std.testing.expectEqual(@as(i32, 2), pane.ed_undo[0].ovl.?.row);
    try std.testing.expectEqualStrings("kept edit", pane.ovl.?.text);
}

test "tag prompt entry and cancellation preserve exact text and cursor state" {
    const Case = struct { key: ?Key = null, save: bool = false, marker: []const u8 };
    const cases = [_]Case{
        .{ .marker = config.search_marker },
        .{ .save = true, .marker = config.save_marker ++ "/dír space/" },
        .{ .key = .{ .cp = '|' }, .marker = config.pipe_marker },
        .{ .key = .{ .cp = '|', .alt = true }, .marker = config.pipe_marker_to },
        .{ .key = .{ .cp = '!' }, .marker = config.pipe_marker_insert },
        .{ .key = .{ .cp = '!', .alt = true }, .marker = config.pipe_marker_append },
    };
    const p = try Pardes.init(std.testing.allocator, .{ .tty_only = true, .cols = 40, .rows = 12 });
    defer p.deinit();
    const pane = try p.setTestFile("one\ntwo\n");
    try pane.setOwnedCwd("/dír space");
    const tail = " keep";
    for (cases) |case| {
        @memcpy(pane.tag_tail[0..tail.len], tail);
        pane.tag_tail_len = tail.len;
        pane.tag_init = true;
        pane.tag_sel = true;
        pane.tag_col = 1;
        pane.cur_row = 1;
        pane.cur_col = 2;
        pane.cur_pinned = true;
        if (case.key) |key| {
            p.update(.{ .key = key });
        } else if (case.save) {
            p.startPrompt(pane, .save);
        } else {
            p.startPrompt(pane, .{ .search = config.search_marker });
        }
        try std.testing.expect(pane.tag_edit);
        try std.testing.expect(!pane.tag_sel);
        try std.testing.expectEqual(.insert, pane.mode);
        try std.testing.expectEqualDeep(modal.Normal.State{}, pane.normal);
        try std.testing.expectEqualStrings(tail, pane.tag_tail[0..tail.len]);
        try std.testing.expectEqualStrings(case.marker, pane.tag_tail[tail.len..pane.tag_tail_len]);
        try std.testing.expectEqual(pane.file.?.path.len + pane.tag_tail_len, pane.tag_col);
        p.update(.{ .key = .{ .cp = Key.escape } });
        try std.testing.expect(pane.prompt == .none);
        try std.testing.expect(!pane.tag_edit);
        try std.testing.expectEqual(.normal, pane.mode);
        try std.testing.expectEqualStrings(tail, pane.tag_tail[0..pane.tag_tail_len]);
        try std.testing.expectEqual(@as(i32, 1), pane.cur_row);
        try std.testing.expectEqual(@as(i32, 2), pane.cur_col);
        try std.testing.expectEqualStrings("one\ntwo\n", pane.file.?.content);
    }
}

test "tag prompt capacity refusal leaves the existing tail and input state untouched" {
    const p = try Pardes.init(std.testing.allocator, .{ .tty_only = true });
    defer p.deinit();
    const pane = try p.setTestFile("one\n");
    @memset(&pane.tag_tail, 'x');
    pane.tag_tail_len = pane.tag_tail.len - 1;
    pane.tag_init = true;
    pane.tag_col = 17;
    pane.tag_sel = true;
    for (0..3) |case| {
        switch (case) {
            0 => p.startPrompt(pane, .{ .search = config.search_marker }),
            1 => p.startPrompt(pane, .save),
            else => p.update(.{ .key = .{ .cp = '|' } }),
        }
        try std.testing.expect(pane.prompt == .none);
        try std.testing.expect(!pane.tag_edit);
        try std.testing.expect(pane.tag_sel);
        try std.testing.expectEqual(.normal, pane.mode);
        try std.testing.expectEqual(@as(u16, 17), pane.tag_col);
        try std.testing.expectEqual(pane.tag_tail.len - 1, pane.tag_tail_len);
        for (pane.tag_tail) |byte| try std.testing.expectEqual(@as(u8, 'x'), byte);
    }
}

test "generated output refuses every pipe prompt before seeding the tag" {
    const p = try Pardes.init(std.testing.allocator, .{ .tty_only = true });
    defer p.deinit();
    const content = try p.gpa.dupe(u8, "generated\n");
    const pane = try panes.Output.open(p, 1, "/", .{ .cmd = .Help }, "", content);
    p.active = 1;
    for ([_]Key{ .{ .cp = '|' }, .{ .cp = '|', .alt = true }, .{ .cp = '!' }, .{ .cp = '!', .alt = true } }) |key| {
        p.update(.{ .key = key });
        try std.testing.expect(pane.prompt == .none);
        try std.testing.expect(!pane.tag_init);
        try std.testing.expect(!pane.tag_edit);
        try std.testing.expectEqualStrings("generated\n", pane.file.?.content);
    }
}

test "tag prompt owns the pipe behavior through cancellation and submission" {
    const p = try Pardes.init(std.testing.allocator, .{ .tty_only = true });
    defer p.deinit();
    const pane = try p.setTestFile("one\ntwo\n");
    pane.cur_row = 0;
    pane.cur_col = 2;
    pane.vsel = .{ .active = true, .row = 0, .col = 0, .explicit = true };
    for (std.enums.values(modal.Normal.PipeBehavior)) |how| {
        p.startPrompt(pane, .{ .pipe = .append });
        p.update(.{ .key = .{ .cp = Key.escape } });
        p.startPrompt(pane, .{ .pipe = how });
        try std.testing.expectEqual(how, pane.prompt.pipe.how);
        p.update(.{ .key = .{ .cp = 'c', .text = "cat" } });
        p.update(.{ .key = .{ .cp = Key.enter } });
        const pending = p.pipe_wait orelse return error.MissingPipe;
        try std.testing.expectEqual(how, pending.how);
        try std.testing.expectEqualStrings("cat", pending.command);
        try std.testing.expectEqual(@as(usize, 1), pending.inputs.len);
        try std.testing.expectEqualStrings(if (how.pipes()) "one" else "", pending.inputs[0].bytes);
        try std.testing.expect(pane.prompt == .none);
    }
}

test "tag prompt cancellation restores the selection before regex previews" {
    const p = try Pardes.init(std.testing.allocator, .{ .tty_only = true });
    defer p.deinit();
    const pane = try p.setTestFile("one two one");
    const cases = [_]struct { key: u21, pattern: []const u8, secondary: u8 }{
        .{ .key = 's', .pattern = "one", .secondary = 1 },
        .{ .key = 'S', .pattern = " ", .secondary = 2 },
    };
    for (cases) |case| {
        pane.cur_row = 0;
        pane.cur_col = 10;
        pane.cur_pinned = true;
        pane.vsel = .{ .active = true, .row = 0, .col = 0, .explicit = true };
        pane.nsel = 0;
        p.update(.{ .key = .{ .cp = case.key } });
        try std.testing.expect(pane.prompt == .search);
        p.update(.{ .key = .{ .cp = case.pattern[0], .text = case.pattern } });
        try std.testing.expectEqual(case.secondary, pane.nsel);
        p.update(.{ .key = .{ .cp = Key.escape } });
        try std.testing.expectEqual(@as(u8, 0), pane.nsel);
        try std.testing.expectEqual(@as(u8, 0), pane.nsel_snap);
        try std.testing.expectEqual(@as(i32, 10), pane.cur_col);
        try std.testing.expectEqual(@as(i32, 0), pane.vsel.col);
        try std.testing.expect(pane.vsel.active and pane.vsel.explicit);
        try std.testing.expectEqualStrings("one two one", pane.file.?.content);
    }
}

test "tag prompt prefix allocation failure preserves an already seeded prompt" {
    const Request = @typeInfo(@TypeOf(Pardes.startPrompt)).@"fn".params[2].type.?;
    for ([_]Request{ .{ .search = config.search_marker }, .save, .{ .pipe = .replace }, .{ .pipe = .ignore }, .{ .pipe = .insert }, .{ .pipe = .append } }) |request| {
        var failing = std.testing.FailingAllocator.init(std.testing.allocator, .{});
        const p = try Pardes.init(failing.allocator(), .{ .tty_only = true });
        defer p.deinit();
        const pane = try p.setTestFile("one\n");
        const tail = " keep /prior";
        @memcpy(pane.tag_tail[0..tail.len], tail);
        pane.tag_tail_len = tail.len;
        pane.tag_init = true;
        pane.prompt = .{ .search = 5 };
        pane.tag_edit = true;
        pane.tag_sel = true;
        pane.tag_col = 14;
        pane.tag_anchor = 7;
        pane.normal = .{ .count = 9, .prefix = .goto };
        const previous_prompt = pane.prompt;
        const previous_normal = pane.normal;
        _ = p.scratch.reset(.free_all);
        failing.fail_index = failing.alloc_index;
        p.startPrompt(pane, request);
        try std.testing.expect(failing.has_induced_failure);
        try std.testing.expectEqualDeep(previous_prompt, pane.prompt);
        try std.testing.expectEqualDeep(previous_normal, pane.normal);
        try std.testing.expectEqualStrings(tail, pane.tag_tail[0..pane.tag_tail_len]);
        try std.testing.expect(pane.tag_edit and pane.tag_sel);
        try std.testing.expectEqual(.normal, pane.mode);
        try std.testing.expectEqual(@as(u16, 14), pane.tag_col);
        try std.testing.expectEqual(@as(u16, 7), pane.tag_anchor);
    }
}

test "tag prompt Save requires room for its complete directory prefix" {
    const p = try Pardes.init(std.testing.allocator, .{ .tty_only = true });
    defer p.deinit();
    const pane = try p.setTestFile("one\n");
    for ([_][]const u8{ "/dír space", "/dír space/", "" }) |dir| {
        try pane.setOwnedCwd(dir);
        const slash: usize = @intFromBool(dir.len == 0 or dir[dir.len - 1] != '/');
        const needed = config.save_marker.len + dir.len + slash;
        for ([_]usize{ 1, 0 }) |shortfall| {
            @memset(&pane.tag_tail, 'x');
            pane.tag_tail_len = pane.tag_tail.len - needed + shortfall;
            pane.tag_init = true;
            pane.tag_edit = false;
            pane.tag_sel = true;
            pane.tag_col = 17;
            const start = pane.tag_tail_len;
            p.startPrompt(pane, .save);
            if (shortfall != 0) {
                try std.testing.expect(pane.prompt == .none);
                try std.testing.expectEqual(start, pane.tag_tail_len);
                try std.testing.expect(!pane.tag_edit and pane.tag_sel);
                try std.testing.expectEqual(@as(u16, 17), pane.tag_col);
                for (pane.tag_tail) |byte| try std.testing.expectEqual(@as(u8, 'x'), byte);
            } else {
                try std.testing.expect(pane.prompt == .save);
                try std.testing.expectEqual(pane.tag_tail.len, pane.tag_tail_len);
                try std.testing.expectEqualStrings(config.save_marker, pane.tag_tail[start..][0..config.save_marker.len]);
                try std.testing.expectEqualStrings(dir, pane.tag_tail[start + config.save_marker.len ..][0..dir.len]);
                try std.testing.expectEqual(@as(u8, '/'), pane.tag_tail[pane.tag_tail_len - 1]);
                p.update(.{ .key = .{ .cp = Key.escape } });
            }
        }
    }
}

test "tag prompt successful seeded entry needs one scratch allocation" {
    const Request = @typeInfo(@TypeOf(Pardes.startPrompt)).@"fn".params[2].type.?;
    for ([_]Request{ .{ .search = config.search_marker }, .save, .{ .pipe = .replace }, .{ .pipe = .ignore }, .{ .pipe = .insert }, .{ .pipe = .append } }) |request| {
        var failing = std.testing.FailingAllocator.init(std.testing.allocator, .{});
        const p = try Pardes.init(failing.allocator(), .{ .tty_only = true });
        defer p.deinit();
        const pane = try p.setTestFile("one\n");
        pane.tag_tail_len = 0;
        pane.tag_init = true;
        _ = p.scratch.reset(.free_all);
        const before = failing.alloc_index;
        p.startPrompt(pane, request);
        try std.testing.expectEqual(before + 1, failing.alloc_index);
        try std.testing.expect(pane.tag_edit and pane.mode == .insert);
    }
}

test "tag prompt failure may initialize only the default tail" {
    const Request = @typeInfo(@TypeOf(Pardes.startPrompt)).@"fn".params[2].type.?;
    for ([_]Request{ .{ .search = config.search_marker }, .save, .{ .pipe = .replace }, .{ .pipe = .ignore }, .{ .pipe = .insert }, .{ .pipe = .append } }) |request| {
        var saw_seeded_failure = false;
        var succeeded = false;
        for (0..16) |failure| {
            var failing = std.testing.FailingAllocator.init(std.testing.allocator, .{});
            const p = try Pardes.init(failing.allocator(), .{ .tty_only = true });
            defer p.deinit();
            const pane = try p.setTestFile("one\n");
            const path = try p.gpa.dupe(u8, "/" ++ "a" ** 2048 ++ ".zig");
            p.gpa.free(pane.file.?.path);
            pane.file.?.path = path;
            p.seedTail(pane);
            try std.testing.expect(pane.tag_init);
            const default_tail = pane.tag_tail;
            const default_len = pane.tag_tail_len;
            pane.tag_init = false;
            pane.tag_tail_len = 0;
            pane.tag_col = 17;
            pane.tag_sel = true;
            pane.normal = .{ .count = 9, .prefix = .goto };
            const previous_normal = pane.normal;
            _ = p.scratch.reset(.free_all);
            failing.fail_index = failing.alloc_index + failure;
            p.startPrompt(pane, request);
            if (!failing.has_induced_failure) {
                try std.testing.expect(pane.tag_edit and pane.mode == .insert);
                succeeded = true;
                break;
            }
            try std.testing.expect(pane.prompt == .none);
            try std.testing.expect(!pane.tag_edit and pane.tag_sel);
            try std.testing.expectEqual(.normal, pane.mode);
            try std.testing.expectEqualDeep(previous_normal, pane.normal);
            try std.testing.expectEqual(@as(u16, 17), pane.tag_col);
            if (pane.tag_init) {
                saw_seeded_failure = true;
                try std.testing.expectEqualStrings(default_tail[0..default_len], pane.tag_tail[0..pane.tag_tail_len]);
            } else try std.testing.expectEqual(@as(usize, 0), pane.tag_tail_len);
        }
        try std.testing.expect(succeeded and saw_seeded_failure);
    }
}

test "file history construction failures preserve existing panes" {
    const Case = enum { open, restore, output, tutor, replace };
    for (std.enums.values(Case)) |case| {
        var succeeded = false;
        for (0..32) |failure| {
            var failing = std.testing.FailingAllocator.init(std.testing.allocator, .{});
            const p = try Pardes.init(failing.allocator(), .{ .tty_only = true, .cols = 40, .rows = 12 });
            defer p.deinit();
            const original = try p.setTestFile("original\n");
            const old_history = original.file.?.history;
            const serial = p.next_serial;
            var path_buffer: [128]u8 = undefined;
            const path = try std.fmt.bufPrint(&path_buffer, "/virtual/pane/{d}/body", .{original.serial});
            var incoming: ?[]u8 = if (case == .output) try p.gpa.dupe(u8, "generated\n") else null;
            defer if (incoming) |bytes| p.gpa.free(bytes);
            failing.fail_index = failing.alloc_index + failure;
            const result = switch (case) {
                .open => panes.File.open(p, 1, path, 0),
                .restore => panes.File.restore(p, 1, .{
                    .kind = .file,
                    .tag = "",
                    .body = "",
                    .file = .{ .path = "/restored.zig", .content = "restored\n" },
                }),
                .output => panes.Output.open(p, 1, "/", .{ .cmd = .Help }, "", incoming.?),
                .tutor => p.openTutorView(1),
                .replace => p.setTestFile("replacement\n"),
            };
            if (result) |pane| {
                if (case == .output) incoming = null;
                try std.testing.expect(pane.file.?.history != old_history);
                try std.testing.expectEqual(@as(usize, 0), pane.file.?.history.undo_len);
                try std.testing.expectEqual(@as(usize, 0), pane.file.?.history.redo_len);
                succeeded = true;
                break;
            } else |err| {
                try std.testing.expect(err == error.OutOfMemory or (case == .open and err == error.WriteFailed and failing.has_induced_failure));
                try std.testing.expectEqual(original, p.panes[0].?);
                try std.testing.expectEqual(old_history, original.file.?.history);
                try std.testing.expectEqualStrings("original\n", original.file.?.content);
                try std.testing.expectEqual(serial, p.next_serial);
                try std.testing.expect(p.panes[1] == null);
                try std.testing.expect(!p.reserved_slots[1]);
            }
        }
        try std.testing.expect(succeeded);
    }
}

test "file history owns bounded snapshot storage without per-edit bookkeeping allocations" {
    var failing = std.testing.FailingAllocator.init(std.testing.allocator, .{});
    const p = try Pardes.init(failing.allocator(), .{ .tty_only = true, .cols = 40, .rows = 12 });
    defer p.deinit();
    const pane = try p.setTestFile("initial");
    const file = &pane.file.?;
    const history = file.history;
    for (0..pardes.memory.limits.undo_max + 2) |index| {
        const next = try std.fmt.allocPrint(p.gpa, "{d}", .{index});
        const before = failing.alloc_index;
        panes.File.pushUndo(p, pane);
        try std.testing.expectEqual(before + 1, failing.alloc_index);
        panes.File.setContent(p, file, next);
        try std.testing.expectEqual(history, file.history);
    }
    try std.testing.expectEqual(pardes.memory.limits.undo_max, history.undo_len);
    try std.testing.expectEqualStrings("1", history.undo[0].content);
    const current = file.content;
    failing.fail_index = failing.alloc_index;
    panes.File.pushUndo(p, pane);
    panes.File.undo(p, pane);
    try std.testing.expectEqual(current.ptr, file.content.ptr);
    try std.testing.expectEqual(pardes.memory.limits.undo_max, history.undo_len);
    try std.testing.expectEqual(@as(usize, 0), history.redo_len);
    failing.fail_index = std.math.maxInt(usize);
    const before = failing.alloc_index;
    panes.File.undo(p, pane);
    try std.testing.expectEqual(before + 2, failing.alloc_index);
    try std.testing.expectEqual(@as(usize, 1), file.line_starts.len);
    try std.testing.expectEqual(@as(usize, 1), history.redo_len);
    const undone = file.content;
    failing.fail_index = failing.alloc_index;
    panes.File.redo(p, pane);
    try std.testing.expectEqual(undone.ptr, file.content.ptr);
    try std.testing.expectEqual(@as(usize, 1), history.redo_len);
    failing.fail_index = std.math.maxInt(usize);
    const before_redo = failing.alloc_index;
    panes.File.redo(p, pane);
    try std.testing.expectEqual(before_redo + 2, failing.alloc_index);
    try std.testing.expectEqual(pardes.memory.limits.undo_max, history.undo_len);
    try std.testing.expectEqual(@as(usize, 0), history.redo_len);
}

test "file history allocation precedes a filesystem read with side effects" {
    var failing = std.testing.FailingAllocator.init(std.testing.allocator, .{});
    const p = try Pardes.init(failing.allocator(), .{ .tty_only = true, .cols = 40, .rows = 12 });
    defer p.deinit();
    const original = p.panes[0].?;
    const serial = p.next_serial;
    failing.fail_index = failing.alloc_index + 2;
    try std.testing.expectError(error.OutOfMemory, panes.File.open(p, 1, "/n/self/new/ctl", 0));
    try std.testing.expect(failing.has_induced_failure);
    try std.testing.expectEqual(original, p.panes[0].?);
    try std.testing.expectEqual(serial, p.next_serial);
    for (p.panes[1..], p.reserved_slots[1..]) |pane, reserved| {
        try std.testing.expect(pane == null);
        try std.testing.expect(!reserved);
    }
}

test "file history survives PDF fallback restoration and allocation failures" {
    const saved =
        \\.{
        \\    .screen = .{ .cols = 40, .rows = 12 },
        \\    .columns = .{.{ .panes = .{0} }},
        \\    .panes = .{.{
        \\        .kind = .image, .tag = "", .body = "",
        \\        .image = .{ .path = "/virtual/missing-history.pdf", .bytes_b64 = "cmF3" },
        \\    }},
        \\}
    ;
    var succeeded = false;
    for (0..256) |failure| {
        var failing = std.testing.FailingAllocator.init(std.testing.allocator, .{ .fail_index = failure });
        if (Pardes.initFromDump(failing.allocator(), .{ .tty_only = true }, saved)) |p| {
            defer p.deinit();
            const pane = p.panes[0].?;
            try std.testing.expect(pane.file != null);
            try std.testing.expectEqualStrings("raw", pane.file.?.content);
            try std.testing.expectEqual(@as(usize, 0), pane.file.?.history.undo_len);
            try std.testing.expectEqual(@as(usize, 0), pane.file.?.history.redo_len);
            if (!failing.has_induced_failure) {
                succeeded = true;
                break;
            }
        } else |err| {
            try std.testing.expect(failing.has_induced_failure);
            try std.testing.expect(err == error.OutOfMemory or err == error.WriteFailed);
        }
    }
    try std.testing.expect(succeeded);
}

test "Save rearms renamed file watches only after a successful write" {
    const Host = struct {
        const Result = enum { success, failure, edited, replaced, closed };
        core: *Pardes,
        result: Result,
        watches: usize = 0,
        err: ?anyerror = null,

        fn write(ctx: ?*anyopaque, id: u8, _: []const u8, _: []const u8) void {
            const h: *@This() = @ptrCast(@alignCast(ctx.?));
            switch (h.result) {
                .success => {},
                .failure => h.core.saveFailed(id, "save", error.PermissionDenied),
                .edited => h.core.panes[id].?.file.?.revision +%= 1,
                .replaced => {
                    const replacement = h.core.setTestFile("replacement\n") catch |err| {
                        h.err = err;
                        return;
                    };
                    replacement.file.?.watch_after_save = true;
                    replacement.file.?.saved_revision -%= 1;
                },
                .closed => {
                    h.core.deinitPane(h.core.panes[id].?) catch |err| {
                        h.err = err;
                        return;
                    };
                    h.core.panes[id] = null;
                },
            }
        }

        fn watch(ctx: ?*anyopaque, _: u8, _: []const u8, on: bool, _: pardes.WatchMode) void {
            const h: *@This() = @ptrCast(@alignCast(ctx.?));
            if (on) h.watches += 1;
        }
    };
    const Case = struct { result: Host.Result, path: []const u8 = "/renamed.zig", watches: usize = 0 };
    for ([_]Case{
        .{ .result = .success, .watches = 1 },
        .{ .result = .success, .path = "/n/os/renamed.zig", .watches = 1 },
        .{ .result = .success, .path = "/virtual/pane/0/body" },
        .{ .result = .success, .path = "/n/remote/file.zig" },
        .{ .result = .failure },
        .{ .result = .edited },
        .{ .result = .replaced },
        .{ .result = .closed },
    }) |case| {
        const p = try Pardes.init(std.testing.allocator, .{ .tty_only = true, .cols = 40, .rows = 12 });
        defer p.deinit();
        const original = try p.setTestFile("edited\n");
        p.gpa.free(original.file.?.path);
        original.file.?.path = try p.gpa.dupe(u8, case.path);
        original.file.?.saved_revision -%= 1;
        original.file.?.watch_after_save = true;
        while (p.nextEffect()) |_| {}
        var host: Host = .{ .core = p, .result = case.result };
        p.host = .{ .ctx = &host, .vtable = &.{ .write_file = Host.write, .watch_file = Host.watch } };
        try std.testing.expect(p.executeBuiltinLine(0, "Save"));
        while (p.nextEffect()) |effect| p.perform(effect);
        if (host.err) |err| return err;
        try std.testing.expectEqual(case.watches, host.watches);
        if (p.panes[0]) |pane| {
            const file = &pane.file.?;
            try std.testing.expectEqual(case.result != .success, file.watch_after_save);
            try std.testing.expectEqual(case.result == .success, file.revision == file.saved_revision);
        } else try std.testing.expectEqual(.closed, case.result);
        if (case.result == .failure) {
            host.result = .success;
            try std.testing.expect(p.executeBuiltinLine(0, "Save"));
            while (p.nextEffect()) |effect| p.perform(effect);
            try std.testing.expectEqual(@as(usize, 1), host.watches);
            try std.testing.expect(!original.file.?.watch_after_save);
            try std.testing.expectEqual(original.file.?.revision, original.file.?.saved_revision);
        }
    }
}

test "Save on a scratch does not watch a path the host could not create" {
    const Refusing = struct {
        fn write(ctx: ?*anyopaque, id: u8, _: []const u8, _: []const u8) void {
            const p: *Pardes = @ptrCast(@alignCast(ctx.?));
            p.saveFailed(id, "save", error.PermissionDenied);
        }
    };
    const p = try Pardes.init(std.testing.allocator, .{ .tty_only = true, .cols = 40, .rows = 12 });
    defer p.deinit();
    try std.testing.expect(p.executeBuiltinLine(0, "New"));
    const id = p.active;
    while (p.nextEffect()) |_| {}
    p.host = .{ .ctx = p, .vtable = &.{ .write_file = Refusing.write } };
    try std.testing.expect(p.executeBuiltinLine(id, "Save /new-file.txt"));
    while (p.nextEffect()) |effect| p.perform(effect);
    const file = &p.panes[id].?.file.?;
    try std.testing.expect(file.output == null);
    try std.testing.expect(file.watch_after_save);
    try std.testing.expect(file.revision != file.saved_revision);
    try std.testing.expect(!p.fallback.watched[id]);
    p.host = .{};
    try std.testing.expect(p.executeBuiltinLine(id, "Save"));
    while (p.nextEffect()) |effect| p.perform(effect);
    try std.testing.expect(!file.watch_after_save);
    try std.testing.expectEqual(file.revision, file.saved_revision);
    try std.testing.expect(p.fallback.watched[id]);
}

test "unplaced terminal panes keep their allocated grid until placement" {
    const p = try Pardes.init(std.testing.allocator, .{ .tty_only = true, .cols = 100, .rows = 30 });
    defer p.deinit();
    p.presentation.enabled = false;
    while (p.nextEffect()) |_| {}
    const id = p.freeSlot().?;
    const pane = try p.newShell(id, "");
    try std.testing.expectEqual(pardes.Rect{}, p.rects[id]);
    p.update(.{ .output = .{ .pane = @intCast(id), .bytes = "unplaced\r\n" } });
    try std.testing.expectEqual(pardes.Rect{}, p.rects[id]);
    try std.testing.expectEqual(@as(u16, 100), pane.cols);
    try std.testing.expectEqual(@as(u16, 30), pane.rows);
    try std.testing.expectEqual(pane.cols, pane.terminal.?.vt.cols);
    try std.testing.expectEqual(pane.rows, pane.terminal.?.vt.rows);
    while (p.nextEffect()) |effect| {
        if (effect == .resize_pty and effect.resize_pty.pane == id) return error.ResizedUnplacedPane;
    }
    pardes.layout.insert(p, 0, 1, id);
    p.update(.tick);
    try std.testing.expect(p.rects[id].w > 0 and p.rects[id].h > pardes.BOX_H);
    try std.testing.expectEqual(p.rects[id].w - config.GUTTER, pane.cols);
    try std.testing.expectEqual(p.rects[id].h - pardes.BOX_H, pane.rows);
}

test "document panes ignore terminal output without allocating terminal state" {
    var allocator = std.testing.FailingAllocator.init(std.testing.allocator, .{});
    const p = try Pardes.init(allocator.allocator(), .{ .tty_only = true });
    defer p.deinit();
    const pane = try p.setTestFile("document body\n");
    while (p.nextEffect()) |_| {}
    const revision = pane.file.?.revision;
    const allocations = allocator.alloc_index;
    const resizes = allocator.resize_index;
    allocator.fail_index = allocations;
    allocator.resize_fail_index = resizes;
    p.update(.{ .output = .{ .pane = 0, .bytes = "unrelated PTY output\r\n" } });
    try std.testing.expect(!allocator.has_induced_failure);
    try std.testing.expectEqual(allocations, allocator.alloc_index);
    try std.testing.expectEqual(resizes, allocator.resize_index);
    try std.testing.expect(pane.terminal == null);
    try std.testing.expectEqual(revision, pane.file.?.revision);
    try std.testing.expectEqualStrings("document body\n", pane.file.?.content);
}

test "removed and recycled pane slots have no stale geometry" {
    const p = try Pardes.init(std.testing.allocator, .{ .tty_only = true, .cols = 100, .rows = 30 });
    defer p.deinit();
    p.presentation.enabled = false;
    const id = p.freeSlot().?;
    const original = try p.newDocPane(id);
    pardes.layout.insert(p, 0, 1, id);
    layout.compute(p);
    try std.testing.expect(p.rects[id].w > 0 and p.rects[id].h > 0);
    layout.removePane(p, id);
    layout.compute(p);
    try std.testing.expectEqual(pardes.Rect{}, p.rects[id]);

    try p.deinitPane(original);
    p.panes[id] = null;
    p.rects[id] = .{ .x = 10, .y = 5, .w = 20, .h = 10 };
    const replacement = try p.newDocPane(id);
    try std.testing.expect(replacement.serial != original.serial);
    try std.testing.expectEqual(pardes.Rect{}, p.rects[id]);
    pardes.layout.insert(p, 0, 1, id);

    for ([_]u16{ 1, 2, 3, 10 }) |size| {
        p.update(.{ .resize = .{ .cols = size, .rows = size } });
        for (p.rects) |rect| {
            try std.testing.expect(rect.x + rect.w <= size);
            try std.testing.expect(rect.y + rect.h <= size);
        }
    }
    p.ncol = 0;
    layout.compute(p);
    for (p.rects) |rect| try std.testing.expectEqual(pardes.Rect{}, rect);
}

const FileTests = struct {
    const graphemeDisplayWidth = panes.File.graphemeDisplayWidth;
    const displayWidth = panes.File.displayWidth;
    const byteAtDisplay = panes.File.byteAtDisplay;
    const rawDisplayCol = panes.File.rawDisplayCol;
    const rawAtDisplay = panes.File.rawAtDisplay;
    const VisualRow = panes.File.VisualRow;
    const visualRow = panes.File.visualRow;

    test "display columns map complete Unicode graphemes" {
        const text = "é界e\u{301}x";
        try std.testing.expectEqual(@as(usize, 5), displayWidth(text));
        try std.testing.expectEqual(@as(usize, 0), byteAtDisplay(text, 0));
        try std.testing.expectEqual(@as(usize, 2), byteAtDisplay(text, 1));
        try std.testing.expectEqual(@as(usize, 2), byteAtDisplay(text, 2));
        try std.testing.expectEqual(@as(usize, 5), byteAtDisplay(text, 3));
        try std.testing.expectEqual(@as(usize, 8), byteAtDisplay(text, 4));
        try std.testing.expectEqual(text.len, byteAtDisplay(text, 5));
        try std.testing.expectEqual(@as(usize, 3), rawDisplayCol(text, 5));
        try std.testing.expectEqual(@as(usize, 5), rawAtDisplay(text, 3));
        try std.testing.expectEqual(@as(usize, 2), graphemeDisplayWidth("👩\u{200d}🚀"));
    }

    test "visual rows partition a line at the breaks the body renders" {
        const line = "abcdefgh";
        try std.testing.expectEqual(VisualRow{ .start = 0, .end = line.len }, visualRow(line, 5, 0));
        try std.testing.expectEqual(VisualRow{ .start = 0, .end = 3 }, visualRow(line, 0, 3));
        try std.testing.expectEqual(VisualRow{ .start = 0, .end = 3 }, visualRow(line, 2, 3));
        try std.testing.expectEqual(VisualRow{ .start = 3, .end = 6 }, visualRow(line, 3, 3));
        // Past the end (a cursor on the newline) names the LAST row, and a short
        // line is one row however narrow the pane is.
        try std.testing.expectEqual(VisualRow{ .start = 6, .end = 8 }, visualRow(line, line.len, 3));
        try std.testing.expectEqual(VisualRow{ .start = 0, .end = 0 }, visualRow("", 0, 3));
        // A grapheme wider than the row still occupies exactly one row.
        try std.testing.expectEqual(VisualRow{ .start = 0, .end = 4 }, visualRow("👩x", 0, 1));
    }
};

const OutputTests = struct {
    const Origin = panes.Output.Origin;
    const max_arg = panes.Output.max_arg;
    const State = panes.Output.State;
    const setArg = panes.Output.setArg;
    const fromWord = panes.Output.fromWord;
    const fillResults = panes.Output.fillResults;

    test "Locations align Unicode paths by display width and preserve source indentation" {
        const p = try Pardes.init(std.testing.allocator, .{ .tty_only = true });
        defer p.deinit();
        _ = try p.setTestFile("notes\n");
        try fillResults(p, 0, "/", .search, "alignment", try p.gpa.dupe(u8, "/界.zig:2:1     first\n/longer-name.zig:12:3 \tsecond\n"), null);
        const result = p.panes[p.panes[0].?.search_pane.?].?;
        const file = &result.file.?;
        try std.testing.expectEqual(@as(usize, 2), file.location_rows.len);
        var column: ?usize = null;
        for (file.location_rows, 0..) |row, i| {
            const line = modal.lineSlice(file.content, i);
            try std.testing.expectEqual(.match, row.kind);
            const current = panes.File.displayWidth(line[0..row.code_start]);
            if (column) |previous| try std.testing.expectEqual(previous, current);
            column = current;
            const expected = if (std.mem.eql(u8, row.path, "/界.zig")) "    first" else "\tsecond";
            try std.testing.expectEqualStrings(expected, line[row.code_start..]);
        }
    }

    test "Locations context uses unsaved sources and navigation visits only matches" {
        if (!syntax.enabled) return error.SkipZigTest;
        const p = try Pardes.init(std.testing.allocator, .{ .tty_only = true, .cols = 100, .rows = 30 });
        defer p.deinit();
        const source = "const Box = struct {\n" ++
            "    pub fn run() void {\n" ++
            "        // unsaved before\n" ++
            "        first();\n" ++
            "        // shared context\n" ++
            "        second();\n" ++
            "        // unsaved after\n" ++
            "    }\n};\n";
        const pane = try TreeContextTests.setZigFile(p, source);
        p.locations_config.context = 1;
        p.locations_config.tscontext = true;
        p.locations_config.tslocations = false;
        const path = pane.file.?.path;
        const input = try std.fmt.allocPrint(p.gpa, "{s}:6:9 second();\n{s}:4:9 first();\n", .{ path, path });
        // Original first result is the later source match: sorting and inserted
        // context must both preserve its anchor.
        try fillResults(p, 0, "/", .search, "context", input, 0);
        const result = p.panes[pane.search_pane.?].?;
        const file = &result.file.?;
        const expected_lines = [_]usize{ 1, 2, 3, 4, 5, 6, 7 };
        try std.testing.expectEqual(expected_lines.len, file.location_rows.len);
        var matches: [2]usize = undefined;
        var count: usize = 0;
        for (file.location_rows, expected_lines, 0..) |row, expected_line, i| {
            try std.testing.expectEqual(expected_line, row.at.line);
            try std.testing.expectEqualStrings(path, row.path);
            const line = modal.lineSlice(file.content, i);
            if (row.kind == .match) {
                matches[count] = i;
                count += 1;
            } else {
                try std.testing.expect(std.mem.startsWith(u8, line, "| "));
                try std.testing.expect(!panes.Output.isResultRow(file, i));
                try std.testing.expectEqualStrings(modal.lineSlice(source, expected_line - 1), line[row.code_start..]);
            }
            if (expected_line <= 2) try std.testing.expectEqual(@as(usize, 0), row.location_end);
        }
        try std.testing.expectEqual(@as(usize, 2), count);
        try std.testing.expectEqual(matches[1], pane.search_row.?);
        try std.testing.expect(pardes.test_api.searchStep(p, 0, -1));
        try std.testing.expectEqual(matches[0], pane.search_row.?);
        try std.testing.expectEqual(@as(i32, 3), pane.cur_row);
        try std.testing.expect(pardes.test_api.searchStep(p, 0, 1));
        try std.testing.expectEqual(matches[1], pane.search_row.?);
        try std.testing.expectEqual(@as(i32, 5), pane.cur_row);
        try std.testing.expect(pardes.test_api.searchStep(p, 0, 1));
        try std.testing.expectEqual(matches[1], pane.search_row.?);

        pane.search_row = null;
        try std.testing.expect(pardes.test_api.searchStep(p, 0, 1));
        try std.testing.expectEqual(matches[0], pane.search_row.?);
        var frame = std.heap.ArenaAllocator.init(p.gpa);
        defer frame.deinit();
        _ = try p.render(frame.allocator());
        const declaration = file.location_rows[0];
        const keyword = declaration.code_start + std.mem.indexOf(u8, modal.lineSlice(source, 0), "struct").?;
        const styles = file.highlights[keyword..][0.."struct".len];
        var colored = false;
        for (styles) |style| colored = colored or style != 0;
        try std.testing.expect(colored);

        try p.dumpState();
        const restored = try Pardes.initFromDump(p.gpa, .{ .tty_only = true }, p.dump_out.?);
        defer restored.deinit();
        const restored_source = restored.panes[0].?;
        const restored_id = pane.search_pane.?;
        const restored_result = restored.panes[restored_id].?;
        const restored_file = &restored_result.file.?;
        try std.testing.expectEqualStrings(file.content, restored_file.content);
        try std.testing.expectEqual(file.location_rows.len, restored_file.location_rows.len);
        for (file.location_rows, restored_file.location_rows) |before, after| {
            try std.testing.expectEqual(before.kind, after.kind);
            try std.testing.expectEqualStrings(before.path, after.path);
            try std.testing.expectEqual(before.at, after.at);
            try std.testing.expectEqual(before.location_end, after.location_end);
            try std.testing.expectEqual(before.code_start, after.code_start);
            try std.testing.expectEqualSlices(u8, before.colors, after.colors);
        }
        _ = try restored.render(frame.allocator());
        try std.testing.expectEqualSlices(u8, styles, restored_file.highlights[keyword..][0.."struct".len]);
        // Search links are transient UI state; the restored output metadata
        // still governs stepping when that output is attached to a source.
        restored_source.search_pane = restored_id;
        restored_source.search_row = null;
        try std.testing.expect(pardes.test_api.searchStep(restored, 0, 1));
        try std.testing.expectEqual(matches[0], restored_source.search_row.?);
        try std.testing.expect(pardes.test_api.searchStep(restored, 0, 1));
        try std.testing.expectEqual(matches[1], restored_source.search_row.?);
        try std.testing.expect(pardes.test_api.searchStep(restored, 0, -1));
        try std.testing.expectEqual(matches[0], restored_source.search_row.?);

        // Once an edit invalidates source metadata, the explicit marker still
        // prevents context declarations from becoming search destinations.
        panes.File.setContent(p, file, try p.gpa.dupe(u8, file.content));
        try std.testing.expectEqual(@as(usize, 0), file.location_rows.len);
        pane.search_row = null;
        try std.testing.expect(pardes.test_api.searchStep(p, 0, 1));
        try std.testing.expectEqual(matches[0], pane.search_row.?);
        try std.testing.expect(pardes.test_api.searchStep(p, 0, 1));
        try std.testing.expectEqual(matches[1], pane.search_row.?);
    }

    test "replacing generated Help clears stale selection before executing a new row" {
        const p = try Pardes.init(std.testing.allocator, .{ .tty_only = true, .cols = 120, .rows = 40 });
        defer p.deinit();
        _ = try p.setTestFile("notes\n");
        p.presentation.enabled = false;
        try std.testing.expect(p.executeBuiltinLine(0, "Help"));
        const id = p.active;
        const help = p.panes[id].?;
        for ("gevkk") |key| p.update(.{ .key = .{ .cp = key } });
        try std.testing.expect(help.vsel.active);
        try std.testing.expect(help.vsel.row > 5);
        try std.testing.expect(help.cur_row != help.vsel.row);
        for (" h?") |key| p.update(.{ .key = .{ .cp = key } });
        try std.testing.expectEqual(id, p.active);
        const content = help.file.?.content;
        try std.testing.expect(std.mem.startsWith(u8, content, "pardes builtins under SPC h\n"));
        const at = std.mem.indexOf(u8, content, "Tutor") orelse return error.MissingTutorRow;
        const row = std.mem.count(u8, content[0..at], "\n");
        const line_start = if (std.mem.lastIndexOfScalar(u8, content[0..at], '\n')) |nl| nl + 1 else 0;
        var frame: std.heap.ArenaAllocator = .init(std.testing.allocator);
        defer frame.deinit();
        _ = try p.render(frame.allocator());
        const rect = p.rects[id];
        const x = rect.x + config.GUTTER + panes.File.gutterWidth(help) + @as(u16, @intCast(at - line_start + 2));
        const y = (if (p.settings.tag_bottom) rect.y else rect.y + pardes.BOX_H) + @as(u16, @intCast(row));
        p.update(.{ .mouse = .{ .button = config.exec_button, .kind = .press, .col = x, .row = y } });
        p.update(.{ .mouse = .{ .button = config.exec_button, .kind = .release, .col = x, .row = y } });
        try std.testing.expect(p.active != id);
        const tutor = p.panes[p.active].?.file orelse return error.MissingTutor;
        try std.testing.expect(std.mem.indexOf(u8, tutor.content, "PARDES TUTOR") != null);
    }

    test "generated result refills preserve unchanged selections and reset changed text" {
        const p = try Pardes.init(std.testing.allocator, .{ .tty_only = true, .cols = 80, .rows = 24 });
        defer p.deinit();
        _ = try p.setTestFile("notes\n");
        const content = "first\nsecond\nthird\n";
        try fillResults(p, 0, "/", .{ .query = .hover }, "", try p.gpa.dupe(u8, content), null);
        const id = for (p.panes, 0..) |slot, id| {
            if (slot != null and slot.?.file != null and slot.?.file.?.output != null) break id;
        } else return error.MissingResults;
        const result = p.panes[id].?;
        p.active = id;
        for ("Cv3") |key| p.update(.{ .key = .{ .cp = key } });
        try std.testing.expect(result.nsel > 0);
        try std.testing.expect(result.select);
        try std.testing.expect(result.vsel.active);
        try std.testing.expect(result.normal.count > 0);
        result.file.?.scroll = 1;
        result.hscroll = 2;
        const selected = result.vsel;
        const selections = result.nsel;
        const cursor_row = result.cur_row;
        const cursor_col = result.cur_col;

        try fillResults(p, 0, "/", .{ .query = .hover }, "", try p.gpa.dupe(u8, content), null);
        try std.testing.expectEqual(selected, result.vsel);
        try std.testing.expectEqual(selections, result.nsel);
        try std.testing.expectEqual(cursor_row, result.cur_row);
        try std.testing.expectEqual(cursor_col, result.cur_col);
        try std.testing.expectEqual(@as(usize, 1), result.file.?.scroll);
        try std.testing.expectEqual(@as(i32, 2), result.hscroll);
        try std.testing.expect(result.normal.count > 0);

        try fillResults(p, 0, "/", .{ .query = .hover }, "", try p.gpa.dupe(u8, "short\n"), null);
        try std.testing.expectEqualStrings("short\n", result.file.?.content);
        try std.testing.expect(!result.vsel.active and !result.msel.active and !result.select);
        try std.testing.expectEqual(@as(u8, 0), result.nsel);
        try std.testing.expectEqual(@as(i32, 0), result.cur_row);
        try std.testing.expectEqual(@as(i32, 0), result.cur_col);
        try std.testing.expectEqual(@as(usize, 0), result.file.?.scroll);
        try std.testing.expectEqual(@as(i32, 0), result.hscroll);
        try std.testing.expectEqual(modal.Normal.State{}, result.normal);
    }

    test "generated result replacement cancels an in-progress body selection" {
        const p = try Pardes.init(std.testing.allocator, .{ .tty_only = true, .cols = 80, .rows = 24 });
        defer p.deinit();
        _ = try p.setTestFile("notes\n");
        p.presentation.enabled = false;
        try fillResults(p, 0, "/", .{ .query = .hover }, "", try p.gpa.dupe(u8, "first\nsecond\nthird\n"), null);
        const id = for (p.panes, 0..) |slot, id| {
            if (slot != null and slot.?.file != null and slot.?.file.?.output != null) break id;
        } else return error.MissingResults;
        const result = p.panes[id].?;
        p.update(.tick);
        var frame: std.heap.ArenaAllocator = .init(std.testing.allocator);
        defer frame.deinit();
        _ = try p.render(frame.allocator());
        p.acknowledgePanelPresentation(&.{});
        const rect = p.rects[id];
        const x = rect.x + config.GUTTER + panes.File.gutterWidth(result);
        const y = if (p.settings.tag_bottom) rect.y else rect.y + pardes.BOX_H;
        p.update(.{ .mouse = .{ .button = config.select_button, .kind = .press, .col = x, .row = y } });
        p.update(.{ .mouse = .{ .button = config.select_button, .kind = .drag, .col = x + 2, .row = y + 1 } });
        try std.testing.expect(p.drag == .select);
        try std.testing.expectEqual(.dragging, result.sel[@intFromEnum(config.select_button)].state);
        try fillResults(p, 0, "/", .{ .query = .hover }, "", try p.gpa.dupe(u8, "short\n"), null);
        try std.testing.expect(p.drag == .none);
        p.update(.{ .mouse = .{ .button = config.select_button, .kind = .release, .col = x + 2, .row = y + 1 } });
        for (result.sel) |selection| try std.testing.expectEqual(.none, selection.state);
        try std.testing.expect(!result.vsel.active and !result.msel.active);
    }

    test "dump origins accept only builtins that actually own output panes" {
        try std.testing.expectEqual(Origin{ .cmd = .Help }, fromWord("Help").?);
        try std.testing.expect(fromWord("Kill") == null);
        try std.testing.expect(fromWord("Theme") == null);
    }

    test "result refill identity retains the full bounded argument" {
        const p = try Pardes.init(std.testing.allocator, .{
            .tty_only = true,
            .cols = 80,
            .rows = 24,
        });
        defer p.deinit();

        var first: [max_arg]u8 = @splat('a');
        var second = first;
        first[200] = 'x';
        second[200] = 'y';

        try fillResults(
            p,
            0,
            "/tmp",
            .search,
            &first,
            try p.gpa.dupe(u8, "first\n"),
            null,
        );
        const first_id = p.panes[0].?.search_pane orelse return error.MissingResults;
        const next_slot = p.freeSlot();

        try fillResults(
            p,
            0,
            "/tmp",
            .search,
            &first,
            try p.gpa.dupe(u8, "refilled\n"),
            null,
        );
        try std.testing.expectEqual(first_id, p.panes[0].?.search_pane.?);
        try std.testing.expectEqual(next_slot, p.freeSlot());
        try std.testing.expectEqualStrings("refilled\n", p.panes[first_id].?.file.?.content);

        try fillResults(
            p,
            0,
            "/tmp",
            .search,
            &second,
            try p.gpa.dupe(u8, "second\n"),
            null,
        );
        try std.testing.expect(p.panes[0].?.search_pane.? != first_id);

        var output: State = .{ .from = .search };
        var oversized: [max_arg + 1]u8 = @splat('z');
        try std.testing.expectError(error.ArgumentTooLong, setArg(&output, &oversized));
        const slot_before_error = p.freeSlot();
        try std.testing.expectError(
            error.ArgumentTooLong,
            fillResults(
                p,
                0,
                "/tmp",
                .search,
                &oversized,
                try p.gpa.dupe(u8, "must be freed\n"),
                null,
            ),
        );
        try std.testing.expectEqual(slot_before_error, p.freeSlot());
    }
};

const ImageTests = struct {
    const State = panes.Image.State;
    const restore = panes.Image.restore;
    const toggleGlyphArt = panes.Image.toggleGlyphArt;
    const togglePalette = panes.Image.togglePalette;
    const toggleAscii = panes.Image.toggleAscii;
    const tagPrefix = panes.Image.tagPrefix;
    const legacySavedPrefix = panes.Image.legacySavedPrefix;

    test "pane-local renderer choices are visible in the image tag" {
        var state: State = .{ .path = @constCast("/tmp/picture.ppm") };
        toggleGlyphArt(&state);
        togglePalette(&state);
        toggleAscii(&state);
        const tag = try tagPrefix(std.testing.allocator, &state);
        defer std.testing.allocator.free(tag);
        try std.testing.expectEqualStrings(
            config.tag_image ++ " petscii:on palette:terminal ascii:off /tmp/picture.ppm",
            tag,
        );
        try std.testing.expectEqualStrings(
            "img /tmp/picture.ppm",
            legacySavedPrefix(&state, "img /tmp/picture.ppm Keep Del").?,
        );
    }

    test "dump restore propagates malformed embedded image bytes" {
        const p = try pardes.Pardes.init(std.testing.allocator, .{ .tty_only = true });
        defer p.deinit();
        try std.testing.expect(p.panes[1] == null);
        try std.testing.expectError(error.InvalidCharacter, restore(p, 1, .{
            .kind = .image,
            .tag = "img /tmp/bad.ppm",
            .body = "",
            .image = .{ .path = "/tmp/bad.ppm", .bytes_b64 = "A..A" },
        }));
        try std.testing.expect(p.panes[1] == null);
    }
};

const PdfTests = struct {
    const enabled = panes.Pdf.enabled;
    const pdf = panes.Pdf.pdf;
    const Point = panes.Pdf.Point;
    const Document = panes.Pdf.Document;
    const isPath = panes.Pdf.isPath;
    const legacySavedPrefix = panes.Pdf.legacySavedPrefix;
    const State = panes.Pdf.State;
    const probeWord = panes.Pdf.probeWord;
    const pointAtGeometry = panes.Pdf.pointAtGeometry;
    const SectionRows = panes.Pdf.SectionRows;

    test "PDF dump paths are recognized independent of MuPDF support" {
        try std.testing.expect(isPath("manual.pdf"));
        try std.testing.expect(isPath("MANUAL.PDF"));
        try std.testing.expect(!isPath("manual.pdf.txt"));
        try std.testing.expect(!isPath("pdf"));
    }

    test "legacy PDF prefix is delimited by its stable marker and exact path" {
        const path = "/tmp/a document.pdf";
        const tag = "pdf 2/9 height PdfFit full PdfTint PdfSections " ++ path ++ " Keep Del";
        try std.testing.expectEqualStrings(
            "pdf 2/9 height PdfFit full PdfTint PdfSections " ++ path,
            legacySavedPrefix(path, tag).?,
        );
    }

    test "feature-off PDF state is zero-sized" {
        if (!enabled) try std.testing.expectEqual(@as(usize, 0), @sizeOf(State));
    }

    test "compact PDF saved prefix separates page status from editable commands" {
        const path = "/tmp/a document.pdf";
        try std.testing.expectEqualStrings(path ++ " [2/9]", legacySavedPrefix(path, path ++ " [2/9] Keep Del").?);
        try std.testing.expect(legacySavedPrefix(path, path ++ " [oops] Keep Del") == null);
        try std.testing.expect(legacySavedPrefix(path, path ++ " [2/9/4] Keep Del") == null);
    }

    test "PDF section rows preserve DFS ordinals and sanitise hierarchy" {
        if (!enabled) return;
        const entries = [_]pdf.OutlineEntry{
            .{ .depth = 0, .title = null, .is_open = true, .flags = 0, .color = @splat(0), .destination = .none },
            .{ .depth = 1, .title = " Child\n\tTitle\x01 Café \u{2028} Next ", .is_open = false, .flags = 0, .color = @splat(0), .destination = .{ .internal = .{ .page = 2, .x = 12, .y = 34 } } },
            .{ .depth = 0, .title = "", .is_open = false, .flags = 0, .color = @splat(0), .destination = .{ .internal = .{ .page = 0, .x = null, .y = null } } },
            .{ .depth = 0, .title = "External", .is_open = false, .flags = 0, .color = @splat(0), .destination = .{ .external = "https://example.com/manual" } },
            .{ .depth = 0, .title = "Dead branch", .is_open = false, .flags = 0, .color = @splat(0), .destination = .none },
            .{ .depth = 0, .title = "Unsafe", .is_open = false, .flags = 0, .color = @splat(0), .destination = .{ .external = "javascript:alert" } },
            .{ .depth = 0, .title = "Linked branch", .is_open = true, .flags = 0, .color = @splat(0), .destination = .none },
            .{ .depth = 1, .title = "Deep link", .is_open = false, .flags = 0, .color = @splat(0), .destination = .{ .external = "https://example.com/deep" } },
        };
        const rows = try SectionRows.render(std.testing.allocator, "/tmp/manual.pdf", &entries);
        defer std.testing.allocator.free(rows);
        try std.testing.expectEqualStrings(
            "manual.pdf:3:1 [untitled]\n" ++
                "manual.pdf:3:2   Child Title Café Next\n" ++
                "manual.pdf:1:3 [empty title]\n" ++
                "https://example.com/manual External\n" ++
                "https://example.com/deep Linked branch\n" ++
                "https://example.com/deep   Deep link\n",
            rows,
        );
        try std.testing.expect(SectionRows.resolve(&entries, 4) == null);
        try std.testing.expect(SectionRows.resolve(&entries, 5) == null);
        const resolved = try SectionRows.resolveOrdinals(std.testing.allocator, &entries);
        defer std.testing.allocator.free(resolved);
        for (entries, 0..) |_, ordinal| {
            const single = SectionRows.resolve(&entries, ordinal);
            if (resolved[ordinal] == std.math.maxInt(usize)) {
                try std.testing.expect(single == null);
            } else {
                const bulk = SectionRows.usableDestination(entries[resolved[ordinal]].destination) orelse
                    return error.MissingBulkPdfSectionDestination;
                try std.testing.expect(single != null);
                try std.testing.expect(std.meta.eql(single.?, bulk));
            }
        }

        // Every allocation site in the ordinal table and output growth remains
        // atomic: the testing allocator sees each induced failure cleaned up
        // before the first index at which the whole render can succeed.
        var rendered = false;
        for (0..64) |fail_index| {
            var failing = std.testing.FailingAllocator.init(std.testing.allocator, .{
                .fail_index = fail_index,
            });
            const failure_gpa = failing.allocator();
            const attempt = SectionRows.render(failure_gpa, "/tmp/manual.pdf", &entries) catch |err| {
                try std.testing.expectEqual(error.OutOfMemory, err);
                continue;
            };
            failure_gpa.free(attempt);
            rendered = true;
            break;
        }
        try std.testing.expect(rendered);
    }

    test "bulk PDF section resolution matches single Look policy across DFS boundaries" {
        if (!enabled) return;
        const entries = [_]pdf.OutlineEntry{
            .{ .depth = 0, .title = "Resolved root", .is_open = true, .flags = 0, .color = @splat(0), .destination = .none },
            .{ .depth = 1, .title = "Unsafe branch", .is_open = true, .flags = 0, .color = @splat(0), .destination = .{ .external = "javascript:unsafe" } },
            .{ .depth = 2, .title = "Safe grandchild", .is_open = false, .flags = 0, .color = @splat(0), .destination = .{ .internal = .{ .page = 1, .x = 4, .y = 8 } } },
            .{ .depth = 1, .title = "Unresolved child", .is_open = false, .flags = 0, .color = @splat(0), .destination = .none },
            .{ .depth = 1, .title = "Sibling", .is_open = false, .flags = 0, .color = @splat(0), .destination = .{ .internal = .{ .page = 2, .x = null, .y = null } } },
            .{ .depth = 0, .title = "Unresolved root", .is_open = false, .flags = 0, .color = @splat(0), .destination = .none },
            .{ .depth = 0, .title = "Next root", .is_open = false, .flags = 0, .color = @splat(0), .destination = .{ .internal = .{ .page = 3, .x = null, .y = null } } },
        };
        const bulk = try SectionRows.resolveOrdinals(std.testing.allocator, &entries);
        defer std.testing.allocator.free(bulk);
        const none = std.math.maxInt(usize);
        try std.testing.expectEqualSlices(usize, &.{ 2, none, 2, none, 4, none, 6 }, bulk);
        for (entries, 0..) |_, ordinal| {
            const single = SectionRows.resolve(&entries, ordinal);
            if (bulk[ordinal] == none) {
                try std.testing.expect(single == null);
            } else {
                const destination = SectionRows.usableDestination(entries[bulk[ordinal]].destination) orelse
                    return error.MissingBoundaryPdfSectionDestination;
                try std.testing.expect(single != null);
                try std.testing.expect(std.meta.eql(single.?, destination));
            }
        }
    }

    test "PDF word probe owns quads and text without a selection object" {
        if (comptime !enabled) return;
        var document = try Document.open("docs/design.pdf");
        defer document.deinit();
        var found = try document.search(std.testing.allocator, 0, "Pardes");
        defer found.deinit(std.testing.allocator);
        const quad = found.quads[0].quad;
        const point = Point{
            .x = (quad.ul.x + quad.ur.x + quad.ll.x + quad.lr.x) / 4,
            .y = (quad.ul.y + quad.ur.y + quad.ll.y + quad.lr.y) / 4,
        };

        // Exactly one shared probe exercises the primitive used by both UI paths;
        // click-vs-hover equivalence belongs to production structure, not a second
        // test that can only restate this MuPDF result.
        var probe = (try probeWord(&document, std.testing.allocator, 0, point)) orelse
            return error.MissingPdfWordProbe;
        defer probe.deinit(std.testing.allocator);
        try std.testing.expectEqual(@as(usize, 0), probe.page);
        try std.testing.expect(probe.quads.len > 0);
        try std.testing.expect(std.ascii.indexOfIgnoreCase(probe.text, "Pardes") != null);
    }

    test "PDF point mapping restores band origin and fractional placement" {
        if (comptime !enabled) return;
        const point = pointAtGeometry(
            .{
                .src = .{ .x = 20, .y = 10, .w = 40, .h = 20 },
                .dst = .{ .x = 100, .y = 30, .w = 80, .h = 20 },
            },
            -0.5,
            200,
            200,
            80,
            120,
            34,
            false,
        ) orelse return error.MissingPdfMappedPoint;
        // x: src 30; y: band 80 + local src 14. The returned coordinates address
        // pixel centers, matching MuPDF's normalized page-space contract.
        try std.testing.expectApproxEqAbs(@as(f32, 30.5 / 200.0), point.x, 0.000_001);
        try std.testing.expectApproxEqAbs(@as(f32, 94.5 / 200.0), point.y, 0.000_001);
    }
};

const TerminalTests = struct {
    // Tests asserting raw ANSI indices explicitly select helix, whose palette
    // is inherited. Native-palette coverage lives in the overlay/eviction and
    // trailing-blank tests and checks their concrete RGB values instead.
    const gridOffset = panes.Terminal.gridOffset;
    const scrollGrid = panes.Terminal.scrollGrid;
    const promptInputReady = panes.Terminal.promptInputReady;
    const forwardKey = panes.Terminal.forwardKey;
    const enterTty = panes.Terminal.enterTty;

    // Align normal-mode glyphs with the VT grid and compare their styles.
    fn modeStyleDiffs(p: *Pardes, pane: *Pane, gpa: std.mem.Allocator, note: []const u8) !usize {
        var frame = std.heap.ArenaAllocator.init(gpa);
        defer frame.deinit();
        const r = p.rects[0];
        const tx = r.x + config.GUTTER;
        const body_y = if (p.settings.tag_bottom) r.y else r.y + pardes.BOX_H;
        const rows: usize = r.h - pardes.BOX_H;
        const cols: usize = r.w -| config.GUTTER;

        const Snap = struct { text: [][7]u8, len: []u8, style: []pardes.CellStyle };
        const glyphAt = struct {
            fn f(sn: Snap, i: usize) []const u8 {
                return sn.text[i][0..sn.len[i]];
            }
        }.f;
        var shot: [2]Snap = undefined;
        for (&shot) |*sn| {
            sn.text = try gpa.alloc([7]u8, rows * cols);
            sn.len = try gpa.alloc(u8, rows * cols);
            sn.style = try gpa.alloc(pardes.CellStyle, rows * cols);
        }
        defer for (&shot) |*sn| {
            gpa.free(sn.text);
            gpa.free(sn.len);
            gpa.free(sn.style);
        };

        for ([_]pardes.Pane.Mode{ .tty, .normal }, 0..) |mode, i| {
            pane.mode = mode;
            p.shell_rows.stale = true;
            _ = frame.reset(.retain_capacity);
            const s = try p.render(frame.allocator());
            for (0..rows) |row| for (0..cols) |col| {
                const cell = s.at(tx + @as(u16, @intCast(col)), body_y + @as(u16, @intCast(row)));
                shot[i].text[row * cols + col] = cell.text;
                shot[i].len[row * cols + col] = cell.len;
                shot[i].style[row * cols + col] = cell.style;
            };
        }

        var diffs: usize = 0;
        for (0..rows) |row| {
            const base = row * cols;
            // The glyph run normal mode shows, and where it ends.
            var last: ?usize = null;
            for (0..cols) |col| {
                if (!std.mem.eql(u8, glyphAt(shot[1], base + col), " ")) last = col;
            }
            const end = last orelse continue; // blank row: nothing to align

            // Recover the shift: the first offset at which tty mode spells the same
            // run. Zero for every row no prompt was hugged out of.
            const shift = shift: {
                var s: usize = 0;
                while (s + end < cols) : (s += 1) {
                    var all = true;
                    for (0..end + 1) |col| {
                        if (!std.mem.eql(u8, glyphAt(shot[1], base + col), glyphAt(shot[0], base + col + s))) {
                            all = false;
                            break;
                        }
                    }
                    if (all) break :shift s;
                }
                var tty_row: [256]u8 = undefined;
                var nrm_row: [256]u8 = undefined;
                var tn: usize = 0;
                var nn: usize = 0;
                for (0..cols) |col| {
                    const tg = glyphAt(shot[0], base + col);
                    const ng = glyphAt(shot[1], base + col);
                    if (tn + tg.len < tty_row.len) {
                        @memcpy(tty_row[tn..][0..tg.len], tg);
                        tn += tg.len;
                    }
                    if (nn + ng.len < nrm_row.len) {
                        @memcpy(nrm_row[nn..][0..ng.len], ng);
                        nn += ng.len;
                    }
                }
                std.debug.print("\n[{s}] row {d} unalignable\n   tty: '{s}'\nnormal: '{s}'\n", .{ note, row, tty_row[0..tn], nrm_row[0..nn] });
                diffs += 1;
                break :shift null;
            } orelse continue;

            // Every column the shift can reach, not just the ones holding a glyph:
            // a cell with a background and no text (`\x1b[41m\x1b[K`, a padded
            // table cell) carries colour too, and is exactly what a shell paints
            // most of.
            for (0..cols - shift) |col| {
                const want = shot[0].style[base + col + shift];
                const got = shot[1].style[base + col];
                if (std.meta.eql(want, got)) continue;
                if (diffs < 6) std.debug.print(
                    "\n[{s}] row {d} col {d} (shift {d}) glyph '{s}': tty fg={any} bg={any} rev={} ul={any} | normal fg={any} bg={any} rev={} ul={any}",
                    .{ note, row, col, shift, glyphAt(shot[1], base + col), want.fg, want.bg, want.reverse, want.ul, got.fg, got.bg, got.reverse, got.ul },
                );
                diffs += 1;
            }
        }
        if (diffs > 0) std.debug.print("\n[{s}] {d} style mismatches\n", .{ note, diffs });
        return diffs;
    }

    test "fresh-shell greeting waits for OSC 133 B input phase" {
        if (pardes.platform == .web) return;
        const p = try Pardes.init(std.testing.allocator, .{ .cols = 80, .rows = 24 });
        defer p.deinit();
        const pane = p.panes[0].?;
        while (p.nextEffect()) |_| {} // initial spawn

        p.update(.{ .resize = .{ .cols = 80, .rows = 24 } });
        while (p.nextEffect()) |effect| switch (effect) {
            .write => return error.GreetedBeforeOutput,
            else => {},
        };
        p.update(.{ .output = .{ .pane = 0, .bytes = "startup banner\r\n" } });
        while (p.nextEffect()) |effect| switch (effect) {
            .write => return error.GreetedBeforePrompt,
            else => {},
        };
        p.update(.{ .output = .{ .pane = 0, .bytes = "\x1b]133;A\x07prompt$ " } });
        try std.testing.expect(!promptInputReady(pane));
        while (p.nextEffect()) |effect| switch (effect) {
            .write => return error.GreetedDuringPrompt,
            else => {},
        };

        p.update(.{ .output = .{ .pane = 0, .bytes = "\x1b]133;B\x07" } });
        try std.testing.expect(promptInputReady(pane));
        var greeted = false;
        while (p.nextEffect()) |effect| switch (effect) {
            .write => |write| greeted = greeted or std.mem.eql(u8, write.bytes.slice(), "ls\r"),
            else => {},
        };
        try std.testing.expect(greeted);
        try std.testing.expect(!pane.greet);
    }

    test "fresh-shell commands preserve order and wait for OSC 133 B" {
        if (pardes.platform == .web) return;
        const p = try Pardes.init(std.testing.allocator, .{ .tty_only = true });
        defer p.deinit();
        while (p.nextEffect()) |_| {} // the host has not acknowledged spawn yet

        try std.testing.expectEqual(@as(?usize, 0), p.execute(0, "echo first"));
        try std.testing.expectEqual(@as(?usize, 0), p.execute(0, "echo second"));
        while (p.nextEffect()) |effect| switch (effect) {
            .write => return error.CommandEscapedBeforeFork,
            else => {},
        };

        p.acknowledgeShell(0, "/bin/bash", true);
        while (p.nextEffect()) |effect| switch (effect) {
            .write => return error.CommandEscapedBeforePrompt,
            else => {},
        };
        p.update(.{ .output = .{ .pane = 0, .bytes = "startup\r\n\x1b]133;A\x07prompt$ " } });
        while (p.nextEffect()) |effect| switch (effect) {
            .write => return error.CommandEscapedDuringPrompt,
            else => {},
        };

        p.update(.{ .output = .{ .pane = 0, .bytes = "\x1b]133;B\x07" } });
        var sent: [64]u8 = undefined;
        var sent_len: usize = 0;
        while (p.nextEffect()) |effect| switch (effect) {
            .write => |write| {
                const bytes = write.bytes.slice();
                @memcpy(sent[sent_len..][0..bytes.len], bytes);
                sent_len += bytes.len;
            },
            else => {},
        };
        try std.testing.expectEqualStrings("echo first\recho second\r", sent[0..sent_len]);
        try std.testing.expectEqual(.none, p.panes[0].?.pending_command.wait);
    }

    test "unmarked fresh shells omit the automatic greeting" {
        if (pardes.platform == .web) return;
        const p = try Pardes.init(std.testing.allocator, .{});
        defer p.deinit();
        const pane = p.panes[0].?;
        while (p.nextEffect()) |_| {}
        try std.testing.expect(pane.greet);

        p.acknowledgeShell(0, "/bin/sh", false);
        try std.testing.expect(!pane.greet);
        try std.testing.expectEqual(.none, pane.pending_command.wait);
        p.update(.{ .output = .{ .pane = 0, .bytes = "plain prompt$ " } });
        while (p.nextEffect()) |effect| switch (effect) {
            .write => return error.UnmarkedGreetingEscaped,
            else => {},
        };
    }

    test "raw terminal keys encode text controls and special sequences" {
        const p = try Pardes.init(std.testing.allocator, .{ .tty_only = true });
        defer p.deinit();
        while (p.nextEffect()) |_| {}

        const Case = struct { key: Key, expected: ?[]const u8 };
        const cases = [_]Case{
            .{ .key = .{ .cp = 'é', .text = "é" }, .expected = "é" },
            .{ .key = .{ .cp = 'c', .text = "c", .ctrl = true }, .expected = "\x03" },
            .{ .key = .{ .cp = 'C', .text = "C", .ctrl = true }, .expected = "\x03" },
            .{ .key = .{ .cp = '@', .text = "@", .ctrl = true }, .expected = "\x00" },
            .{ .key = .{ .cp = '_', .text = "_", .ctrl = true }, .expected = "\x1f" },
            .{ .key = .{ .cp = '1', .text = "1", .ctrl = true }, .expected = "1" },
            .{ .key = .{ .cp = Key.up, .alt = true, .shift = true }, .expected = "\x1b[1;4A" },
            .{ .key = .{ .cp = Key.delete }, .expected = "\x1b[3~" },
            .{ .key = .{ .cp = Key.home }, .expected = "\x1b[H" },
        };
        for (cases) |case| {
            forwardKey(p, 0, case.key);
            const expected = case.expected orelse {
                try std.testing.expect(p.nextEffect() == null);
                continue;
            };
            const effect = p.nextEffect() orelse return error.MissingWriteEffect;
            switch (effect) {
                .write => |write| {
                    try std.testing.expectEqual(@as(u8, 0), write.pane);
                    try std.testing.expectEqualStrings(expected, write.bytes.slice());
                },
                else => return error.UnexpectedEffect,
            }
            try std.testing.expect(p.nextEffect() == null);
        }
    }

    test "an edit buffer slides shell rows and their colors together" {
        const testing = std.testing;
        const p = try Pardes.init(testing.allocator, .{ .startup_config = "Theme helix\n", .tty_only = true, .cols = 18, .rows = 12 });
        defer p.deinit();
        while (p.nextEffect()) |_| {}
        const pane = p.panes[0].?;
        pane.tty_filter = false;
        pane.mode = .normal;

        p.update(.{ .output = .{ .pane = 0, .bytes = "\x1b[31mAAA\x1b[0m\r\n\x1b[32mBBB\x1b[0m\r\n\x1b[34mCCC\x1b[0m" } });

        var frame = std.heap.ArenaAllocator.init(testing.allocator);
        defer frame.deinit();
        const r = p.rects[0];
        const tx = r.x + config.GUTTER;
        const body_y = if (p.settings.tag_bottom) r.y else r.y + pardes.BOX_H;
        const red: pardes.Color = .{ .index = 1 };
        const green: pardes.Color = .{ .index = 2 };
        const blue: pardes.Color = .{ .index = 4 };

        p.shell_rows.stale = true;
        const before = try p.render(frame.allocator());
        try testing.expectEqual(red, before.at(tx, body_y).style.fg);
        try testing.expectEqual(green, before.at(tx, body_y + 1).style.fg);
        try testing.expectEqual(blue, before.at(tx, body_y + 2).style.fg);

        // Four lines of typed text standing in for the ONE shell row `AAA` was:
        // every row below slides down by three, and `surfRow` is the arithmetic
        // that says so. The colours have to take the same three rows, or `BBB`
        // would be painted green three rows above where it is now drawn.
        pane.ovl = .{ .row = 0, .rows = 1, .text = try p.gpa.dupe(u8, "e\nd\ni\nt") };
        p.shell_rows.stale = true;
        _ = frame.reset(.retain_capacity);
        const after = try p.render(frame.allocator());

        try testing.expectEqualStrings("B", after.at(tx, body_y + 4).grapheme());
        try testing.expectEqualStrings("C", after.at(tx, body_y + 5).grapheme());
        try testing.expectEqual(green, after.at(tx, body_y + 4).style.fg);
        try testing.expectEqual(blue, after.at(tx, body_y + 5).style.fg);

        // ...and the rows the user typed are the user's own text: no shell row
        // sits under them, so nothing projects a colour onto them.
        for (0..4) |i| {
            const cell = after.at(tx, body_y + @as(u16, @intCast(i)));
            try testing.expect(!std.meta.eql(red, cell.style.fg));
            try testing.expect(!std.meta.eql(green, cell.style.fg));
            try testing.expect(!std.meta.eql(blue, cell.style.fg));
        }
    }

    test "a combining mark in the prompt keeps the command and its colors aligned" {
        const testing = std.testing;
        const p = try Pardes.init(testing.allocator, .{ .startup_config = "Theme helix\n", .tty_only = true, .cols = 18, .rows = 6 });
        defer p.deinit();
        while (p.nextEffect()) |_| {}
        const pane = p.panes[0].?;
        pane.tty_filter = false;
        pane.mode = .normal;

        // A ONE-cell prompt carrying a combining mark — an NFD `e` — then `ABC`
        // typed at it. The cell walk that finds the prompt's end must step ONE
        // grapheme for that cell, not one per stored codepoint: stepping twice ate
        // the `A`, and left every colour a cell to the left of its glyph with the
        // last one stranded on a blank.
        p.update(.{ .output = .{ .pane = 0, .bytes = "\x1b]133;A\x1b\\\x1b[32me\u{301}\x1b]133;B\x1b\\\x1b[31mA\x1b[34mB\x1b[35mC" } });

        var frame = std.heap.ArenaAllocator.init(testing.allocator);
        defer frame.deinit();
        const r = p.rects[0];
        const tx = r.x + config.GUTTER;
        const body_y = if (p.settings.tag_bottom) r.y else r.y + pardes.BOX_H;

        p.shell_rows.stale = true;
        const s = try p.render(frame.allocator());
        try testing.expectEqualStrings("A", s.at(tx, body_y).grapheme());
        try testing.expectEqualStrings("B", s.at(tx + 1, body_y).grapheme());
        try testing.expectEqualStrings("C", s.at(tx + 2, body_y).grapheme());
        try testing.expectEqual(pardes.Color{ .index = 1 }, s.at(tx, body_y).style.fg);
        try testing.expectEqual(pardes.Color{ .index = 4 }, s.at(tx + 1, body_y).style.fg);
        try testing.expectEqual(pardes.Color{ .index = 5 }, s.at(tx + 2, body_y).style.fg);
        // ...and no colour past the end of what the row actually says
        try testing.expect(!std.meta.eql(pardes.Color{ .index = 5 }, s.at(tx + 3, body_y).style.fg));
    }

    test "colors are never taken from shell rows below the viewport" {
        const testing = std.testing;
        const p = try Pardes.init(testing.allocator, .{ .startup_config = "Theme helix\n", .tty_only = true, .cols = 18, .rows = 14 });
        defer p.deinit();
        while (p.nextEffect()) |_| {}
        const pane = p.panes[0].?;
        // Raw palette, so a leaked background reads back as `.index` — the theme
        // filter would repaint every blank cell and hide the evidence.
        pane.tty_filter = false;
        pane.mode = .normal;

        // Sixty rows, each a distinct background, so a leaked colour names the row
        // it leaked from.
        for (0..60) |i| {
            var buf: [32]u8 = undefined;
            const bytes = std.fmt.bufPrint(&buf, "\x1b[4{d}mL{d:0>2}\x1b[0m\r\n", .{ (i % 6) + 1, i }) catch unreachable;
            p.update(.{ .output = .{ .pane = 0, .bytes = bytes } });
        }
        p.shell_rows.stale = true;
        scrollGrid(pane, -20);

        // ONE buffer line standing in for SIX shell rows: everything below slides
        // UP five, so the last rows of the body resolve past the viewport's bottom
        // edge. `PageList.pin` answers for those rows anyway — it walks down the
        // pagelist, not the viewport — so without a bound of its own this pass
        // painted the scrollback's colours onto rows the text pass left blank.
        const anchor = gridOffset(pane);
        pane.ovl = .{ .row = anchor, .rows = 6, .text = try p.gpa.dupe(u8, "one") };
        p.shell_rows.stale = true;

        var frame = std.heap.ArenaAllocator.init(testing.allocator);
        defer frame.deinit();
        const r = p.rects[0];
        const tx = r.x + config.GUTTER;
        const body_y = if (p.settings.tag_bottom) r.y else r.y + pardes.BOX_H;
        const body_h = r.h - pardes.BOX_H;

        p.shell_rows.stale = true;
        const s = try p.render(frame.allocator());
        // A body row the text pass left blank has no shell row under it, so no
        // ANSI background may have reached it. Every colour in the payload above is
        // an indexed one, so a leak is exactly an `.index` background on a blank row.
        var vr: u16 = 0;
        while (vr < body_h) : (vr += 1) {
            var blank = true;
            var c: u16 = 0;
            while (c < r.w -| config.GUTTER) : (c += 1) {
                if (!std.mem.eql(u8, " ", s.at(tx + c, body_y + vr).grapheme())) blank = false;
            }
            if (!blank) continue;
            c = 0;
            while (c < r.w -| config.GUTTER) : (c += 1) {
                const bg = s.at(tx + c, body_y + vr).style.bg;
                try testing.expect(std.meta.activeTag(bg) != .index);
            }
        }
    }

    test "a row the edit buffer only swallowed keeps its color" {
        const testing = std.testing;
        const p = try Pardes.init(testing.allocator, .{ .startup_config = "Theme helix\n", .tty_only = true, .cols = 18, .rows = 12 });
        defer p.deinit();
        while (p.nextEffect()) |_| {}
        const pane = p.panes[0].?;
        pane.tty_filter = false;
        pane.mode = .normal;

        p.update(.{ .output = .{ .pane = 0, .bytes = "\x1b[31mAAA\x1b[0m\r\n\x1b[32mBBB\x1b[0m\r\n\x1b[34mCCC\x1b[0m" } });

        var frame = std.heap.ArenaAllocator.init(testing.allocator);
        defer frame.deinit();
        const r = p.rects[0];
        const tx = r.x + config.GUTTER;
        const body_y = if (p.settings.tag_bottom) r.y else r.y + pardes.BOX_H;
        const red: pardes.Color = .{ .index = 1 };
        const green: pardes.Color = .{ .index = 2 };
        const blue: pardes.Color = .{ .index = 4 };

        // The buffer only ever grows, so after a few edits it covers rows nobody
        // touched. Here it spans all three and only the MIDDLE line differs: the
        // first and last are still byte-identical to the shell rows they were
        // seeded from, so they still stand over them and keep their colours.
        pane.ovl = .{ .row = 0, .rows = 3, .text = try p.gpa.dupe(u8, "AAA\nXXX\nCCC") };
        p.shell_rows.stale = true;
        const s = try p.render(frame.allocator());

        try testing.expectEqualStrings("A", s.at(tx, body_y).grapheme());
        try testing.expectEqualStrings("X", s.at(tx, body_y + 1).grapheme());
        try testing.expectEqualStrings("C", s.at(tx, body_y + 2).grapheme());
        try testing.expectEqual(red, s.at(tx, body_y).style.fg);
        try testing.expectEqual(blue, s.at(tx, body_y + 2).style.fg);
        // ...and the line that actually changed is the user's own text now
        try testing.expect(!std.meta.eql(green, s.at(tx, body_y + 1).style.fg));
    }

    test "an edit buffer reaching past the dumped rows colors nothing from row zero" {
        const testing = std.testing;
        const p = try Pardes.init(testing.allocator, .{ .startup_config = "Theme helix\n", .tty_only = true, .cols = 18, .rows = 12 });
        defer p.deinit();
        while (p.nextEffect()) |_| {}
        const pane = p.panes[0].?;
        pane.tty_filter = false;
        pane.mode = .normal;

        p.update(.{ .output = .{ .pane = 0, .bytes = "\x1b[31mAAA\x1b[0m\r\n\x1b[32mBBB\x1b[0m\r\n\x1b[34mCCC\x1b[0m" } });

        var frame = std.heap.ArenaAllocator.init(testing.allocator);
        defer frame.deinit();
        const r = p.rects[0];
        const tx = r.x + config.GUTTER;
        const body_y = if (p.settings.tag_bottom) r.y else r.y + pardes.BOX_H;
        const red: pardes.Color = .{ .index = 1 };

        // Covers far more rows than the grid was ever dumped for, so the anchor
        // table cannot be built and answers "no shell row" for every line. The
        // zeroed table must not read as "the last line sits on the buffer's first
        // row", which claimed row zero's colour and underflowed on every line after.
        pane.ovl = .{ .row = 1, .rows = 50, .text = try p.gpa.dupe(u8, "p\nq\nr") };
        p.shell_rows.stale = true;
        const s = try p.render(frame.allocator());

        try testing.expectEqualStrings("p", s.at(tx, body_y + 1).grapheme());
        var i: u16 = 1;
        while (i <= 3) : (i += 1) {
            try testing.expect(!std.meta.eql(red, s.at(tx, body_y + i).style.fg));
        }
    }

    test "a prompted session keeps every glyph's color in normal mode" {
        const testing = std.testing;
        const payload =
            "\x1b]133;A\x1b\\\x1b[32muser\x1b[34m@host\x1b[35m ~/dir\x1b[0m$ \x1b]133;B\x1b\\\x1b[36mls \x1b[33m-la\x1b[0m\r\n" ++
            "\x1b[34mdir1\x1b[0m  \x1b[32mexec\x1b[0m  plain.txt\r\n" ++
            "\x1b[31merror: nope\x1b[0m\r\n" ++
            "\x1b]133;A\x1b\\\x1b[32muser\x1b[34m@host\x1b[35m ~/dir\x1b[0m$ \x1b]133;B\x1b\\\x1b[36mecho \x1b[1;37mhi\x1b[0m\r\n" ++
            "\x1b[38;5;208mhi\x1b[0m\r\n";

        for ([_]bool{ false, true }) |filter| {
            const p = try Pardes.init(testing.allocator, .{ .tty_only = true, .cols = 44, .rows = 12 });
            defer p.deinit();
            while (p.nextEffect()) |_| {}
            const pane = p.panes[0].?;
            pane.tty_filter = filter;
            p.update(.{ .output = .{ .pane = 0, .bytes = payload } });
            const diffs = try modeStyleDiffs(p, pane, testing.allocator, if (filter) "session filter=on" else "session filter=off");
            try testing.expectEqual(@as(usize, 0), diffs);
        }
    }

    test "an emoji prompt neither eats the command nor slides its colors" {
        const testing = std.testing;
        // ABSOLUTE assertions, not a tty/normal comparison: ghostty and this
        // surface can BOTH be wrong about a cluster's width, and then a differential
        // agrees with itself while the user sees the wrong thing. What is typed at
        // the prompt is what must appear, each character wearing its own colour.
        //
        // Ghostty splits these clusters across cells and spells each one in the row
        // dump, so the cell walk and the byte walk only agree if the byte walk is
        // driven by what each CELL contributed. `👨‍💻` is two wide cells, `👨‍👩‍👧`
        // three, `🇺🇸` two, `👍🏽` two, while all of them print as one glyph here.
        const prompts = [_][]const u8{
            "plain",
            "\u{1F468}\u{200D}\u{1F4BB}", // technologist
            "\u{1F468}\u{200D}\u{1F469}\u{200D}\u{1F467}", // family
            "\u{1F1FA}\u{1F1F8}", // flag
            "\u{1F44D}\u{1F3FD}", // thumbs up, skin tone
            "\u{2764}\u{FE0F}", // heart, VS16
            "\u{0031}\u{FE0F}\u{20E3}", // keycap
            "\u{754C}", // CJK wide
            "e\u{301}", // NFD
        };
        for (prompts) |prompt| {
            for ([_]bool{ false, true }) |filter| {
                const p = try Pardes.init(testing.allocator, .{ .startup_config = "Theme helix\n", .tty_only = true, .cols = 24, .rows = 6 });
                defer p.deinit();
                while (p.nextEffect()) |_| {}
                const pane = p.panes[0].?;
                pane.tty_filter = filter;
                pane.mode = .normal;

                var buf: [256]u8 = undefined;
                const bytes = try std.fmt.bufPrint(
                    &buf,
                    "\x1b]133;A\x1b\\\x1b[32m{s}$ \x1b]133;B\x1b\\\x1b[31mab\x1b[34mcd\x1b[0m",
                    .{prompt},
                );
                p.update(.{ .output = .{ .pane = 0, .bytes = bytes } });

                var frame = std.heap.ArenaAllocator.init(testing.allocator);
                defer frame.deinit();
                const r = p.rects[0];
                const tx = r.x + config.GUTTER;
                const body_y = if (p.settings.tag_bottom) r.y else r.y + pardes.BOX_H;
                p.shell_rows.stale = true;
                const s = try p.render(frame.allocator());

                for ([_][]const u8{ "a", "b", "c", "d" }, 0..) |want, i| {
                    const cell = s.at(tx + @as(u16, @intCast(i)), body_y);
                    testing.expectEqualStrings(want, cell.grapheme()) catch |err| {
                        std.debug.print("\nprompt '{s}' filter={}: col {d}\n", .{ prompt, filter, i });
                        return err;
                    };
                }
                // `ab` was printed red and `cd` blue, so whatever the theme does
                // with those two runs, the pair boundary has to fall between `b`
                // and `c`. A prompt that cost the row a character shows up here as
                // the boundary sliding onto the wrong glyph.
                const fg = [_]pardes.Color{
                    s.at(tx, body_y).style.fg,
                    s.at(tx + 1, body_y).style.fg,
                    s.at(tx + 2, body_y).style.fg,
                    s.at(tx + 3, body_y).style.fg,
                };
                errdefer std.debug.print("\nprompt '{s}' filter={}: fg {any}\n", .{ prompt, filter, fg });
                try testing.expect(std.meta.eql(fg[0], fg[1]));
                try testing.expect(std.meta.eql(fg[2], fg[3]));
                try testing.expect(!std.meta.eql(fg[1], fg[2]));
                if (!filter) {
                    try testing.expectEqual(pardes.Color{ .index = 1 }, fg[0]);
                    try testing.expectEqual(pardes.Color{ .index = 4 }, fg[2]);
                }
            }
        }
    }

    test "background-only cells keep their color through the prompt hug" {
        const testing = std.testing;
        // Backgrounds with no glyph under them are most of what a shell paints:
        // erase-to-end-of-line after a colour is set, padded table cells, and a
        // selected row. They have no text to align on, so they are the cells a
        // column translation is most likely to lose.
        const payload =
            "\x1b]133;A\x1b\\\x1b[32mp\x1b[0m$ \x1b]133;B\x1b\\cmd\x1b[41m\x1b[K\r\n" ++
            "\x1b[44mblue-bg\x1b[K\x1b[0m\r\n" ++
            "a\x1b[42m      \x1b[0mb\r\n" ++
            "\x1b[100;97mbright-on-grey\x1b[0m\r\n" ++
            "\x1b]133;A\x1b\\\x1b[35m>>\x1b[0m \x1b]133;B\x1b\\\x1b[48;5;19mrun\x1b[K\x1b[0m\r\n" ++
            "\x1b[48;2;90;10;10mtruecolor-bg\x1b[K\x1b[0m\r\n";

        for ([_]bool{ false, true }) |filter| {
            const p = try Pardes.init(testing.allocator, .{ .tty_only = true, .cols = 30, .rows = 12 });
            defer p.deinit();
            while (p.nextEffect()) |_| {}
            const pane = p.panes[0].?;
            pane.tty_filter = filter;
            p.update(.{ .output = .{ .pane = 0, .bytes = payload } });
            const diffs = try modeStyleDiffs(p, pane, testing.allocator, if (filter) "bg filter=on" else "bg filter=off");
            try testing.expectEqual(@as(usize, 0), diffs);
        }
    }

    test "a leftover edit buffer does not move what tty mode shows" {
        const testing = std.testing;
        const p = try Pardes.init(testing.allocator, .{ .tty_only = true, .cols = 40, .rows = 14 });
        defer p.deinit();
        while (p.nextEffect()) |_| {}
        const pane = p.panes[0].?;
        pane.tty_filter = false;
        pane.mode = .tty;

        for (0..60) |i| {
            var buf: [40]u8 = undefined;
            const bytes = std.fmt.bufPrint(&buf, "\x1b[3{d}mL{d:0>2}\x1b[0m\r\n", .{ (i % 6) + 1, i }) catch unreachable;
            p.update(.{ .output = .{ .pane = 0, .bytes = bytes } });
        }

        var frame = std.heap.ArenaAllocator.init(testing.allocator);
        defer frame.deinit();
        const r = p.rects[0];
        const tx = r.x + config.GUTTER;
        const body_y = if (p.settings.tag_bottom) r.y else r.y + pardes.BOX_H;
        const rows: usize = r.h - pardes.BOX_H;
        const cols: usize = r.w -| config.GUTTER;

        // What tty mode shows with nothing left behind: the reference.
        p.shell_rows.stale = true;
        const clean = try p.render(frame.allocator());
        const want_text = try testing.allocator.alloc([7]u8, rows * cols);
        defer testing.allocator.free(want_text);
        const want_fg = try testing.allocator.alloc(pardes.Color, rows * cols);
        defer testing.allocator.free(want_fg);
        for (0..rows) |row| for (0..cols) |col| {
            const cell = clean.at(tx + @as(u16, @intCast(col)), body_y + @as(u16, @intCast(row)));
            want_text[row * cols + col] = cell.text;
            want_fg[row * cols + col] = cell.style.fg;
        };

        // `enterTty` clears every other modal remnant but leaves the edit buffer, so
        // a buffer whose covered span STRADDLES the viewport top is an ordinary
        // state. tty mode does not apply the buffer, so it must not be moved by one
        // either — and `surfRow`/`gridRow` are not inverses across that span.
        const anchor = gridOffset(pane);
        pane.ovl = .{ .row = anchor - 1, .rows = 4, .text = try p.gpa.dupe(u8, "one\ntwo") };
        p.shell_rows.stale = true;
        _ = frame.reset(.retain_capacity);
        const after = try p.render(frame.allocator());

        for (0..rows) |row| for (0..cols) |col| {
            const cell = after.at(tx + @as(u16, @intCast(col)), body_y + @as(u16, @intCast(row)));
            try testing.expectEqualStrings(
                std.mem.sliceTo(&want_text[row * cols + col], 0),
                std.mem.sliceTo(&cell.text, 0),
            );
            try testing.expectEqual(want_fg[row * cols + col], cell.style.fg);
        };
    }

    test "a background after a row-final wide glyph lands on the right columns" {
        const testing = std.testing;
        // A CJK glyph then a coloured erase-to-end-of-line, with a second colour
        // partway. The glyph's grid tail spells no bytes, so the pairing walk used
        // to stop ON it and pair every later column with the cell before it: an
        // unpainted hole beside the glyph and every boundary one column right.
        //
        // ABSOLUTE assertions: both modes were wrong identically here, so a
        // tty/normal differential says nothing.
        for ([_]bool{ false, true }) |filter| {
            for ([_]pardes.Pane.Mode{ .tty, .normal }) |mode| {
                const p = try Pardes.init(testing.allocator, .{ .tty_only = true, .cols = 12, .rows = 8 });
                defer p.deinit();
                while (p.nextEffect()) |_| {}
                const pane = p.panes[0].?;
                pane.tty_filter = filter;
                pane.mode = mode;
                p.update(.{ .output = .{ .pane = 0, .bytes = "\x1b[32m\u{754C}\x1b[41m\x1b[K\x1b[7G\x1b[44m\x1b[K\r\n" } });

                var frame = std.heap.ArenaAllocator.init(testing.allocator);
                defer frame.deinit();
                const r = p.rects[0];
                const tx = r.x + config.GUTTER;
                const body_y = if (p.settings.tag_bottom) r.y else r.y + pardes.BOX_H;
                p.shell_rows.stale = true;
                const s = try p.render(frame.allocator());

                try testing.expectEqualStrings("\u{754C}", s.at(tx, body_y).grapheme());
                // The glyph covers columns 0-1; red runs from 2 up to the second
                // erase at column 6 (1-based 7), blue from there to the edge.
                const red = s.at(tx + 3, body_y).style.bg;
                const blue = s.at(tx + 9, body_y).style.bg;
                errdefer std.debug.print("\nmode={any} filter={}: red={any} blue={any} col2={any}\n", .{ mode, filter, red, blue, s.at(tx + 2, body_y).style.bg });
                try testing.expect(!std.meta.eql(red, blue));
                for (2..6) |c| try testing.expectEqual(red, s.at(tx + @as(u16, @intCast(c)), body_y).style.bg);
                for (6..10) |c| try testing.expectEqual(blue, s.at(tx + @as(u16, @intCast(c)), body_y).style.bg);
            }
        }
    }

    test "a colored row reaches its last column when a wide glyph did not fit" {
        const testing = std.testing;
        // Thirteen cells of red background, then a wide glyph with one column left:
        // ghostty leaves a `spacer_head` in that last column, carrying the row's
        // background, and wraps the glyph to the next row. A head OWNS its column,
        // so skipping it the way a tail is skipped left the row's final column bare.
        for ([_]pardes.Pane.Mode{ .tty, .normal }) |mode| {
            const p = try Pardes.init(testing.allocator, .{ .startup_config = "Theme helix\n", .tty_only = true, .cols = 16, .rows = 8 });
            defer p.deinit();
            while (p.nextEffect()) |_| {}
            const pane = p.panes[0].?;
            pane.tty_filter = false;
            pane.mode = mode;
            p.update(.{ .output = .{ .pane = 0, .bytes = "\x1b[41mzzzzzzzzzzzzz\u{754C}\x1b[0m\r\n" } });

            var frame = std.heap.ArenaAllocator.init(testing.allocator);
            defer frame.deinit();
            const r = p.rects[0];
            const tx = r.x + config.GUTTER;
            const body_y = if (p.settings.tag_bottom) r.y else r.y + pardes.BOX_H;
            p.shell_rows.stale = true;
            const s = try p.render(frame.allocator());

            const red: pardes.Color = .{ .index = 1 };
            var c: u16 = 0;
            while (c < r.w -| config.GUTTER) : (c += 1) {
                errdefer std.debug.print("\nmode={any} col {d} bg={any}\n", .{ mode, c, s.at(tx + c, body_y).style.bg });
                try testing.expectEqual(red, s.at(tx + c, body_y).style.bg);
            }
        }
    }

    test "tty colours survive a scrollback deeper than the pane" {
        const testing = std.testing;
        const p = try Pardes.init(testing.allocator, .{ .tty_only = true, .cols = 30, .rows = 12 });
        defer p.deinit();
        while (p.nextEffect()) |_| {}
        const pane = p.panes[0].?;
        pane.tty_filter = false;
        pane.mode = .tty;
        for (0..40) |i| {
            var buf: [64]u8 = undefined;
            const bytes = std.fmt.bufPrint(&buf, "\x1b[38;5;{d}mline-{d:0>2}\x1b[0m\r\n", .{ 20 + i, i }) catch unreachable;
            p.update(.{ .output = .{ .pane = 0, .bytes = bytes } });
        }
        p.shell_rows.stale = true;

        var frame = std.heap.ArenaAllocator.init(testing.allocator);
        defer frame.deinit();
        const s = try p.render(frame.allocator());
        const r = p.rects[0];
        const tx = r.x + config.GUTTER;
        const body_y = if (p.settings.tag_bottom) r.y else r.y + pardes.BOX_H;

        var bad: usize = 0;
        for (0..r.h -| pardes.BOX_H) |vr| {
            var buf: [16]u8 = undefined;
            var n: usize = 0;
            for (0..10) |c| {
                const g = s.at(tx + @as(u16, @intCast(c)), body_y + @as(u16, @intCast(vr))).grapheme();
                if (g.len != 1) break;
                buf[n] = g[0];
                n += 1;
            }
            const txt = buf[0..n];
            if (!std.mem.startsWith(u8, txt, "line-")) continue;
            const num = std.fmt.parseInt(usize, std.mem.trim(u8, txt[5..], " "), 10) catch continue;
            const want = pardes.Color{ .index = @intCast(20 + num) };
            const got = s.at(tx, body_y + @as(u16, @intCast(vr))).style.fg;
            if (!std.meta.eql(want, got)) {
                bad += 1;
                std.debug.print("row {d}: text {s} want {any} got {any}\n", .{ vr, txt, want, got });
            }
        }
        try testing.expectEqual(@as(usize, 0), bad);
    }

    test "reverse video swaps the default colors with the filter off too" {
        const testing = std.testing;
        // DECSCNM is a property of the terminal, not of a cell's SGR, so it has to
        // be honoured on BOTH colour paths. The theme filter folds it into its own
        // palette; the raw path resolves a `.none` colour by role, and simply
        // dropped reverse video altogether.
        for ([_]bool{ false, true }) |filter| {
            const p = try Pardes.init(testing.allocator, .{ .tty_only = true, .cols = 20, .rows = 6 });
            defer p.deinit();
            while (p.nextEffect()) |_| {}
            const pane = p.panes[0].?;
            pane.tty_filter = filter;
            pane.mode = .normal;

            var frame = std.heap.ArenaAllocator.init(testing.allocator);
            defer frame.deinit();
            const r = p.rects[0];
            const tx = r.x + config.GUTTER;
            const body_y = if (p.settings.tag_bottom) r.y else r.y + pardes.BOX_H;

            p.update(.{ .output = .{ .pane = 0, .bytes = "plain text\r\n" } });
            p.shell_rows.stale = true;
            const before = try p.render(frame.allocator());
            const plain = before.at(tx, body_y).style;

            p.update(.{ .output = .{ .pane = 0, .bytes = "\x1b[?5h" } });
            p.shell_rows.stale = true;
            _ = frame.reset(.retain_capacity);
            const after = try p.render(frame.allocator());
            const reversed = after.at(tx, body_y).style;

            errdefer std.debug.print("\nfilter={}: plain fg={any} bg={any} | reversed fg={any} bg={any}\n", .{ filter, plain.fg, plain.bg, reversed.fg, reversed.bg });
            try testing.expectEqual(plain.fg, reversed.bg);
            try testing.expectEqual(plain.bg, reversed.fg);
        }
    }

    test "untouched lines between two edits keep their colors" {
        const testing = std.testing;
        const p = try Pardes.init(testing.allocator, .{ .tty_only = true, .cols = 24, .rows = 14 });
        defer p.deinit();
        while (p.nextEffect()) |_| {}
        const pane = p.panes[0].?;
        pane.tty_filter = false;
        pane.mode = .normal;

        for (0..6) |i| {
            var buf: [40]u8 = undefined;
            const bytes = std.fmt.bufPrint(&buf, "\x1b[38;5;{d}mrow-{d:0>2}\x1b[0m\r\n", .{ 16 + i, i }) catch unreachable;
            p.update(.{ .output = .{ .pane = 0, .bytes = bytes } });
        }

        var frame = std.heap.ArenaAllocator.init(testing.allocator);
        defer frame.deinit();
        const r = p.rects[0];
        const tx = r.x + config.GUTTER;
        const body_y = if (p.settings.tag_bottom) r.y else r.y + pardes.BOX_H;

        // The state two ordinary edits reach: one at the bottom, one that split a
        // line further up. The buffer now spans rows 2..6 and diverges at BOTH
        // ends, with three untouched lines in the middle. Matching a leading and a
        // trailing run stops at the first divergence and drains exactly those three;
        // each line carries its own evidence, so each is anchored on its own.
        pane.ovl = .{ .row = 2, .rows = 5, .text = try p.gpa.dupe(u8, "r\now-02\nrow-03\nrow-04\nrow-05\nZ") };
        p.shell_rows.stale = true;
        const s = try p.render(frame.allocator());

        // body row 2+k shows buffer line k; lines 2..4 are `row-03`..`row-05`
        for (0..3) |k| {
            const vr = @as(u16, @intCast(4 + k));
            var buf: [8]u8 = undefined;
            const want_text = std.fmt.bufPrint(&buf, "row-{d:0>2}", .{3 + k}) catch unreachable;
            const cell = s.at(tx, body_y + vr);
            errdefer std.debug.print("\nbody row {d}: glyph '{s}' fg {any}\n", .{ vr, cell.grapheme(), cell.style.fg });
            try testing.expectEqualStrings(want_text[0..1], cell.grapheme());
            try testing.expectEqual(pardes.Color{ .index = @intCast(19 + k) }, cell.style.fg);
        }
    }

    test "an emptied edit buffer does not shift the colors below it" {
        const testing = std.testing;
        const p = try Pardes.init(testing.allocator, .{ .startup_config = "Theme helix\n", .tty_only = true, .cols = 18, .rows = 12 });
        defer p.deinit();
        while (p.nextEffect()) |_| {}
        const pane = p.panes[0].?;
        pane.tty_filter = false;
        pane.mode = .normal;

        p.update(.{ .output = .{ .pane = 0, .bytes = "\x1b[31m000\x1b[0m\r\n\x1b[32m111\x1b[0m\r\n\r\n\x1b[34m333\x1b[0m\r\n\x1b[35m444\x1b[0m" } });

        var frame = std.heap.ArenaAllocator.init(testing.allocator);
        defer frame.deinit();
        const r = p.rects[0];
        const tx = r.x + config.GUTTER;
        const body_y = if (p.settings.tag_bottom) r.y else r.y + pardes.BOX_H;

        // The state three keystrokes reach on any blank shell row: type a character
        // and delete it, and the buffer holds NO text while still standing in for
        // the row. `modal.lineCount("")` is 0 while `splitScalar("")` yields one
        // line, so anything deriving the slide from the former puts every colour
        // below here one row too far down — and drops the bottom row's entirely.
        pane.ovl = .{ .row = 2, .rows = 1, .text = try p.gpa.dupe(u8, "") };
        p.shell_rows.stale = true;
        const s = try p.render(frame.allocator());

        try testing.expectEqualStrings("3", s.at(tx, body_y + 3).grapheme());
        try testing.expectEqualStrings("4", s.at(tx, body_y + 4).grapheme());
        try testing.expectEqual(pardes.Color{ .index = 4 }, s.at(tx, body_y + 3).style.fg);
        try testing.expectEqual(pardes.Color{ .index = 5 }, s.at(tx, body_y + 4).style.fg);
        // ...and the user's own empty line takes no colour from the row beneath it
        try testing.expect(!std.meta.eql(pardes.Color{ .index = 4 }, s.at(tx, body_y + 2).style.fg));
    }

    test "an edit overlay never changes tty-mode ansi colors" {
        const testing = std.testing;
        const p = try Pardes.init(testing.allocator, .{ .startup_config = "Theme helix\n", .tty_only = true, .cols = 18, .rows = 6 });
        defer p.deinit();
        while (p.nextEffect()) |_| {}
        const pane = p.panes[0].?;
        pane.tty_filter = false;
        pane.mode = .tty;

        p.update(.{ .output = .{ .pane = 0, .bytes = "\x1b[31mAAA\x1b[0m\r\n\x1b[32mBBB\x1b[0m\r\n\x1b[34mCCC\x1b[0m" } });

        var frame = std.heap.ArenaAllocator.init(testing.allocator);
        defer frame.deinit();
        const r = p.rects[0];
        const tx = r.x + config.GUTTER;
        const body_y = if (p.settings.tag_bottom) r.y else r.y + pardes.BOX_H;
        const blue: pardes.Color = .{ .index = 4 };

        p.shell_rows.stale = true;
        const before = try p.render(frame.allocator());
        try testing.expectEqualStrings("C", before.at(tx, body_y + 2).grapheme());
        try testing.expectEqual(blue, before.at(tx, body_y + 2).style.fg);

        // A lingering multi-line edit overlay must not move any shell row's colour.
        pane.ovl = .{ .row = 0, .rows = 1, .text = try p.gpa.dupe(u8, "e\nd\ni\nt") };
        p.shell_rows.stale = true;
        _ = frame.reset(.retain_capacity);
        const after = try p.render(frame.allocator());
        try testing.expectEqualStrings("C", after.at(tx, body_y + 2).grapheme());
        try testing.expectEqual(blue, after.at(tx, body_y + 2).style.fg);
    }

    test "an edited row keeps the colours of the bytes the edit did not touch" {
        const testing = std.testing;
        // The loudest colour bug this editor had: one keystroke anywhere in a
        // coloured row turned EVERY column of it grey, because an anchor was all or
        // nothing. The row's own bytes survive at both ends of what was typed, and
        // being the same bytes they keep the same colours; only the typed character
        // has no cell under it and so takes none.
        const p = try Pardes.init(testing.allocator, .{ .tty_only = true, .cols = 30, .rows = 12 });
        defer p.deinit();
        while (p.nextEffect()) |_| {}
        const pane = p.panes[0].?;
        pane.tty_filter = false;
        pane.mode = .normal;
        for (0..6) |i| {
            var buf: [64]u8 = undefined;
            const bytes = std.fmt.bufPrint(&buf, "\x1b[38;5;{d}mrow-{d}-abcdefgh\x1b[0m\r\n", .{ 30 + i, i }) catch unreachable;
            p.update(.{ .output = .{ .pane = 0, .bytes = bytes } });
        }
        // One `Z` typed into the middle of row 3's own text.
        pane.ovl = .{ .row = 3, .rows = 1, .text = try p.gpa.dupe(u8, "row-3-abcZdefgh") };
        p.shell_rows.stale = true;

        var frame = std.heap.ArenaAllocator.init(testing.allocator);
        defer frame.deinit();
        const r = p.rects[0];
        const tx = r.x + config.GUTTER;
        const body_y = if (p.settings.tag_bottom) r.y else r.y + pardes.BOX_H;

        const s = try p.render(frame.allocator());
        const want = pardes.Color{ .index = 33 };
        var seen = false;
        for (0..@as(usize, r.h -| pardes.BOX_H)) |vr| {
            var buf: [15]u8 = undefined;
            for (0..15) |c| {
                const g = s.at(tx + @as(u16, @intCast(c)), body_y + @as(u16, @intCast(vr))).grapheme();
                buf[c] = if (g.len == 1) g[0] else '?';
            }
            if (!std.mem.eql(u8, &buf, "row-3-abcZdefgh")) continue;
            seen = true;
            for (0..15) |c| {
                const got = s.at(tx + @as(u16, @intCast(c)), body_y + @as(u16, @intCast(vr))).style.fg;
                errdefer std.debug.print("\nedited row col {d} ('{c}') fg={any}\n", .{ c, buf[c], got });
                // Column 9 is the typed `Z`; every other column is row 3's own.
                if (c == 9) try testing.expect(!std.meta.eql(want, got)) else try testing.expectEqual(want, got);
            }
        }
        try testing.expect(seen);
    }

    test "joining two rows leaves the rows below them their colours" {
        const testing = std.testing;
        // A join removes a buffer line while the buffer's covered span GROWS, so the
        // two counts cancel at `lines == covered`. Anchoring that only counts down
        // from the buffer's top and up from its bottom then resolves both ways to
        // the SAME row, one short of where the lines below live, and every untouched
        // row under the join went plain. This is the state four keystrokes reach
        // (Enter, then a backspace two rows up), taken from the fuzzer that found it.
        const p = try Pardes.init(testing.allocator, .{ .tty_only = true, .cols = 34, .rows = 14 });
        defer p.deinit();
        while (p.nextEffect()) |_| {}
        const pane = p.panes[0].?;
        pane.tty_filter = false;
        pane.mode = .normal;
        for (0..26) |i| {
            var buf: [64]u8 = undefined;
            const bytes = std.fmt.bufPrint(&buf, "\x1b[38;5;{d}mrow-{d:0>2}-xyzzy\x1b[0m\r\n", .{ 20 + i, i }) catch unreachable;
            p.update(.{ .output = .{ .pane = 0, .bytes = bytes } });
        }
        pane.ovl = .{
            .row = 23,
            .rows = 4,
            .text = try p.gpa.dupe(u8, "row-23-xyzzyrow-24-xyzzy\nrow-25-xyzzy\n\n"),
        };
        p.shell_rows.stale = true;

        var frame = std.heap.ArenaAllocator.init(testing.allocator);
        defer frame.deinit();
        const r = p.rects[0];
        const tx = r.x + config.GUTTER;
        const body_y = if (p.settings.tag_bottom) r.y else r.y + pardes.BOX_H;

        const s = try p.render(frame.allocator());
        var seen = false;
        for (0..@as(usize, r.h -| pardes.BOX_H)) |vr| {
            var buf: [12]u8 = undefined;
            for (0..12) |c| {
                const g = s.at(tx + @as(u16, @intCast(c)), body_y + @as(u16, @intCast(vr))).grapheme();
                buf[c] = if (g.len == 1) g[0] else '?';
            }
            if (!std.mem.eql(u8, &buf, "row-25-xyzzy")) continue;
            seen = true;
            // The join is above it and its own text is untouched, so every column
            // still carries row 25's own colour.
            for (0..12) |c| {
                const got = s.at(tx + @as(u16, @intCast(c)), body_y + @as(u16, @intCast(vr))).style.fg;
                errdefer std.debug.print("\nrow-25 col {d} fg={any}\n", .{ c, got });
                try testing.expectEqual(pardes.Color{ .index = 45 }, got);
            }
        }
        try testing.expect(seen);
    }

    test "an untouched row always carries the colour its own text names" {
        const testing = std.testing;
        // Random editing, absolute oracle: every row's own text names the colour it
        // must have, so no sequence of keystrokes may leave an UNTOUCHED row wearing
        // anything else. This is what found the join above, and the empty line that
        // claimed a blank row far below it and took every coloured row in between
        // out of reach of the lines that owned them.
        var seed: u64 = 0;
        while (seed < 40) : (seed += 1) {
            var prng = std.Random.DefaultPrng.init(seed);
            const rand = prng.random();

            const p = try Pardes.init(testing.allocator, .{ .tty_only = true, .cols = 34, .rows = 14 });
            defer p.deinit();
            while (p.nextEffect()) |_| {}
            const pane = p.panes[0].?;
            // The raw palette, so a row's text names its exact colour instead of one
            // this test would have to re-derive from the theme.
            pane.tty_filter = false;
            pane.mode = .normal;
            for (0..26) |i| {
                var buf: [64]u8 = undefined;
                const bytes = std.fmt.bufPrint(&buf, "\x1b[38;5;{d}mrow-{d:0>2}-xyzzy\x1b[0m\r\n", .{ 20 + i, i }) catch unreachable;
                p.update(.{ .output = .{ .pane = 0, .bytes = bytes } });
            }
            p.shell_rows.stale = true;

            var frame = std.heap.ArenaAllocator.init(testing.allocator);
            defer frame.deinit();
            const r = p.rects[0];
            const tx = r.x + config.GUTTER;
            const body_y = if (p.settings.tag_bottom) r.y else r.y + pardes.BOX_H;
            const body_h = r.h -| pardes.BOX_H;

            var step: usize = 0;
            while (step < 12) : (step += 1) {
                _ = frame.reset(.retain_capacity);
                const s = try p.render(frame.allocator());
                for (0..body_h) |vr| {
                    var buf: [24]u8 = undefined;
                    for (0..24) |c| {
                        const g = s.at(tx + @as(u16, @intCast(c)), body_y + @as(u16, @intCast(vr))).grapheme();
                        buf[c] = if (g.len == 1) g[0] else '?';
                    }
                    const txt = std.mem.trimEnd(u8, buf[0..24], " ");
                    if (txt.len != 12) continue;
                    if (!std.mem.startsWith(u8, txt, "row-") or !std.mem.endsWith(u8, txt, "-xyzzy")) continue;
                    const num = std.fmt.parseInt(usize, txt[4..6], 10) catch continue;
                    const want = pardes.Color{ .index = @intCast(20 + num) };
                    for (0..txt.len) |c| {
                        const got = s.at(tx + @as(u16, @intCast(c)), body_y + @as(u16, @intCast(vr))).style.fg;
                        errdefer std.debug.print("\nseed {d} step {d}: untouched '{s}' col {d} fg={any}\n", .{ seed, step, txt, c, got });
                        try testing.expectEqual(want, got);
                    }
                }

                switch (rand.intRangeAtMost(u8, 0, 10)) {
                    0 => p.update(.{ .key = .{ .cp = pardes.Key.up } }),
                    1 => p.update(.{ .key = .{ .cp = pardes.Key.down } }),
                    2 => p.update(.{ .key = .{ .cp = pardes.Key.left } }),
                    3 => p.update(.{ .key = .{ .cp = pardes.Key.right } }),
                    4 => {
                        p.update(.{ .key = .{ .cp = 'i', .text = "i" } });
                        p.update(.{ .key = .{ .cp = 'Q', .text = "Q" } });
                        p.update(.{ .key = .{ .cp = pardes.Key.escape } });
                    },
                    5 => {
                        p.update(.{ .key = .{ .cp = 'i', .text = "i" } });
                        p.update(.{ .key = .{ .cp = pardes.Key.enter } });
                        p.update(.{ .key = .{ .cp = pardes.Key.escape } });
                    },
                    6 => {
                        p.update(.{ .key = .{ .cp = 'i', .text = "i" } });
                        p.update(.{ .key = .{ .cp = pardes.Key.backspace } });
                        p.update(.{ .key = .{ .cp = pardes.Key.escape } });
                    },
                    7 => {
                        p.update(.{ .key = .{ .cp = 'i', .text = "i" } });
                        p.update(.{ .key = .{ .cp = 'W', .text = "W" } });
                        p.update(.{ .key = .{ .cp = 'W', .text = "W" } });
                        p.update(.{ .key = .{ .cp = pardes.Key.escape } });
                    },
                    8 => p.update(.{ .key = .{ .cp = pardes.Key.home } }),
                    9 => p.update(.{ .key = .{ .cp = pardes.Key.end } }),
                    else => {
                        p.update(.{ .key = .{ .cp = 'i', .text = "i" } });
                        p.update(.{ .key = .{ .cp = pardes.Key.delete } });
                        p.update(.{ .key = .{ .cp = pardes.Key.escape } });
                    },
                }
                while (p.nextEffect()) |_| {}
            }
        }
    }

    test "a new empty line does not take the colours of the rows below it" {
        const testing = std.testing;
        // Splitting a row makes an EMPTY buffer line, and empty equals every blank
        // row in the buffer's span - including the one under the last output. Left
        // free to look ahead for a row spelling the same bytes, that line claimed
        // the blank row far below and put every coloured row in between out of
        // reach of the lines that owned them. Two keystrokes (Home, Enter) got here.
        const p = try Pardes.init(testing.allocator, .{ .tty_only = true, .cols = 34, .rows = 14 });
        defer p.deinit();
        while (p.nextEffect()) |_| {}
        const pane = p.panes[0].?;
        pane.tty_filter = false;
        pane.mode = .normal;
        for (0..26) |i| {
            var buf: [64]u8 = undefined;
            const bytes = std.fmt.bufPrint(&buf, "\x1b[38;5;{d}mrow-{d:0>2}-xyzzy\x1b[0m\r\n", .{ 20 + i, i }) catch unreachable;
            p.update(.{ .output = .{ .pane = 0, .bytes = bytes } });
        }
        // A newline typed at column 0 of row 24, and `WW` typed on the blank row
        // below the output: the span covers rows 24, 25 and that blank row.
        pane.ovl = .{
            .row = 24,
            .rows = 3,
            .text = try p.gpa.dupe(u8, "\nrow-24-xyzzy\nrow-25-xyzzy\nWW"),
        };
        p.shell_rows.stale = true;

        var frame = std.heap.ArenaAllocator.init(testing.allocator);
        defer frame.deinit();
        const r = p.rects[0];
        const tx = r.x + config.GUTTER;
        const body_y = if (p.settings.tag_bottom) r.y else r.y + pardes.BOX_H;

        const s = try p.render(frame.allocator());
        var seen: usize = 0;
        for (0..@as(usize, r.h -| pardes.BOX_H)) |vr| {
            var buf: [12]u8 = undefined;
            for (0..12) |c| {
                const g = s.at(tx + @as(u16, @intCast(c)), body_y + @as(u16, @intCast(vr))).grapheme();
                buf[c] = if (g.len == 1) g[0] else '?';
            }
            if (!std.mem.startsWith(u8, &buf, "row-2")) continue;
            const num = std.fmt.parseInt(usize, buf[4..6], 10) catch continue;
            if (num != 24 and num != 25) continue;
            seen += 1;
            const got = s.at(tx, body_y + @as(u16, @intCast(vr))).style.fg;
            errdefer std.debug.print("\nrow-{d} fg={any}\n", .{ num, got });
            try testing.expectEqual(pardes.Color{ .index = @intCast(20 + num) }, got);
        }
        try testing.expectEqual(@as(usize, 2), seen);
    }
};

test {
    _ = TagNavigationTests;
    _ = TagNameTintTests;
    _ = TreeContextTests;
    _ = BodyHitTests;
    _ = TtySelectionTests;
    _ = ClickCursorTests;
    _ = JumpSelectionTests;
    _ = @import("output.zig");
    _ = @import("pdf.zig");
    _ = @import("fs_namespace.zig");
    _ = @import("hxdiff.zig");
    _ = FileTests;
    _ = OutputTests;
    _ = ImageTests;
    _ = PdfTests;
    _ = TerminalTests;
}

test "an empty counted paste leaves no count for the next motion" {
    for ([_]bool{ false, true }) |empty_register| {
        const p = try Pardes.init(std.testing.allocator, .{ .tty_only = true, .cols = 60, .rows = 12 });
        defer p.deinit();
        const pane = try p.setTestFile("abcdefgh\n");
        if (empty_register) p.yank = try p.gpa.dupe(u8, "");
        for ("3p") |cp| p.update(.{ .key = .{ .cp = cp } });
        try std.testing.expectEqual(modal.Normal.State{}, pane.normal);
        p.update(.{ .key = .{ .cp = 'l' } });
        try std.testing.expectEqual(@as(i32, 1), pane.cur_col);
        try std.testing.expectEqualStrings("abcdefgh\n", pane.file.?.content);
    }
}

test "cancelled normal gestures leave no count or subprefix after mouse and focus changes" {
    const Gesture = enum { body, tag, focus, last };
    for ([_][]const u8{ "3", "3g", "mr(" }) |keys| {
        for ([_]Gesture{ .body, .tag, .focus, .last }) |gesture| {
            errdefer std.debug.print("\nkeys={s} gesture={s}\n", .{ keys, @tagName(gesture) });
            const p = try Pardes.init(std.testing.allocator, .{ .tty_only = true, .cols = 100, .rows = 16 });
            defer p.deinit();
            const pane = try p.setTestFile("abcdefghij\n");
            p.settings.colors = false;
            p.presentation.enabled = false;
            try std.testing.expect(p.executeBuiltinLine(0, "New"));
            const other = p.active;
            try std.testing.expect(layout.splitColumn(p, other, other, false));
            p.active = 0;
            p.update(.tick);
            var frame = std.heap.ArenaAllocator.init(std.testing.allocator);
            defer frame.deinit();
            _ = try p.render(frame.allocator());
            for (keys) |cp| p.update(.{ .key = .{ .cp = cp } });
            try std.testing.expect(!std.meta.eql(modal.Normal.State{}, pane.normal));
            switch (gesture) {
                .body, .tag => {
                    const rect = p.rects[0];
                    const tag_y = if (p.settings.tag_bottom) rect.y + rect.h - pardes.BOX_H else rect.y;
                    const body_y = if (p.settings.tag_bottom) rect.y else rect.y + pardes.BOX_H;
                    const x = rect.x + config.GUTTER + @as(u16, @intCast(panes.File.gutterWidth(pane))) + 3;
                    const y = if (gesture == .tag) tag_y else body_y;
                    p.update(.{ .mouse = .{ .button = config.select_button, .kind = .press, .col = x, .row = y } });
                    p.update(.{ .mouse = .{ .button = config.select_button, .kind = .release, .col = x, .row = y } });
                    if (gesture == .tag) {
                        try std.testing.expect(pane.tag_edit);
                        p.update(.{ .key = .{ .cp = Key.escape } });
                        try std.testing.expect(!pane.tag_edit);
                    }
                },
                .focus, .last => {
                    p.update(.{ .key = .{ .cp = 'w', .ctrl = true } });
                    p.update(.{ .key = .{ .cp = 'l' } });
                    try std.testing.expectEqual(other, p.active);
                    if (gesture == .last) {
                        p.update(.{ .key = .{ .cp = Key.escape } });
                    } else {
                        p.update(.{ .key = .{ .cp = 'w', .ctrl = true } });
                        p.update(.{ .key = .{ .cp = 'h' } });
                    }
                    try std.testing.expectEqual(@as(usize, 0), p.active);
                },
            }
            try std.testing.expectEqual(modal.Normal.State{}, pane.normal);
            const col = pane.cur_col;
            p.update(.{ .key = .{ .cp = 'l' } });
            try std.testing.expectEqual(col + 1, pane.cur_col);
            try std.testing.expectEqualStrings("abcdefghij\n", pane.file.?.content);
        }
    }
}

test "cancelled normal gestures leave no count or subprefix through raw tty mode" {
    for ([_][]const u8{ "3", "3g", "mr(" }) |keys| {
        const p = try Pardes.init(std.testing.allocator, .{ .tty_only = true, .cols = 80, .rows = 12 });
        defer p.deinit();
        const pane = p.panes[0].?;
        pane.mode = .normal;
        p.update(.{ .output = .{ .pane = 0, .bytes = "abcdefghij\r\n" } });
        for (keys) |cp| p.update(.{ .key = .{ .cp = cp } });
        try std.testing.expect(!std.meta.eql(modal.Normal.State{}, pane.normal));
        p.update(.{ .key = .{ .cp = p.opts.tty_toggle, .ctrl = true } });
        try std.testing.expectEqual(pardes.Pane.Mode.tty, pane.mode);
        try std.testing.expectEqual(modal.Normal.State{}, pane.normal);
        p.update(.{ .key = .{ .cp = p.opts.tty_toggle, .ctrl = true } });
        try std.testing.expectEqual(pardes.Pane.Mode.normal, pane.mode);
        try std.testing.expectEqual(modal.Normal.State{}, pane.normal);
    }
}

test "Colors restores syntax after rendering disabled files and disabled edits" {
    if (!syntax.enabled) return error.SkipZigTest;
    const gpa = std.testing.allocator;
    for ([_]bool{ false, true }) |edit_while_disabled| {
        const p = try Pardes.init(gpa, .{ .tty_only = true, .cols = 80, .rows = 12 });
        defer p.deinit();
        const pane = try p.setTestFile("pub fn first() void { if (true) {} }\n");
        const file = &pane.file.?;
        gpa.free(file.path);
        file.path = try gpa.dupe(u8, "/colors.zig");
        p.settings.colors = edit_while_disabled;
        p.presentation.enabled = false;
        var frame = std.heap.ArenaAllocator.init(gpa);
        defer frame.deinit();
        _ = try p.render(frame.allocator());
        if (edit_while_disabled) {
            try std.testing.expect(file.highlights.len > 0);
            p.update(.{ .command = "Colors" });
            panes.File.setContent(p, file, try gpa.dupe(u8, "pub fn edited() void { if (false) {} }\n"));
            _ = frame.reset(.retain_capacity);
            _ = try p.render(frame.allocator());
        }
        try std.testing.expect(!p.settings.colors);
        try std.testing.expectEqual(@as(usize, 0), file.highlights.len);
        try std.testing.expect(!file.syntax_dirty);
        const rect = p.rects[0];
        const cols = pane.cols;
        const rows = pane.rows;
        p.update(.{ .command = "Colors" });
        try std.testing.expectEqual(rect, p.rects[0]);
        try std.testing.expectEqual(cols, pane.cols);
        try std.testing.expectEqual(rows, pane.rows);
        _ = frame.reset(.retain_capacity);
        const surface = try p.render(frame.allocator());
        try std.testing.expect(p.settings.colors);
        try std.testing.expect(file.highlights.len > 0);
        try std.testing.expect(!file.syntax_dirty);
        var seen: usize = 0;
        for (surface.cells[0 .. surface.cells.len - 1], 0..) |*first, i| {
            const second = &surface.cells[i + 1];
            if (!(std.mem.eql(u8, first.grapheme(), "f") and std.mem.eql(u8, second.grapheme(), "n")) and
                !(std.mem.eql(u8, first.grapheme(), "i") and std.mem.eql(u8, second.grapheme(), "f"))) continue;
            seen += 1;
            for ([_]*pardes.Cell{ first, second }) |cell| {
                try std.testing.expectEqual(pardes.Color{ .rgb = p.theme().kw }, cell.style.fg);
                try std.testing.expect(!cell.style.bold);
            }
        }
        try std.testing.expectEqual(@as(usize, 2), seen);
    }
}

test "growing a file pane colors every newly visible Zig keyword" {
    if (!syntax.enabled) return error.SkipZigTest;
    const gpa = std.testing.allocator;
    const p = try Pardes.init(gpa, .{ .tty_only = true, .cols = 80, .rows = 8 });
    defer p.deinit();
    const pane = try p.setTestFile("pub fn f() void { if (true) {} }\n" ** 100);
    const file = &pane.file.?;
    gpa.free(file.path);
    file.path = try gpa.dupe(u8, "/resize.zig");
    p.update(.{ .command = "SyntaxBold" });
    try std.testing.expect(p.settings.syntax_bold);
    p.settings.colors = true;
    p.presentation.enabled = false;
    var frame = std.heap.ArenaAllocator.init(gpa);
    defer frame.deinit();
    _ = try p.render(frame.allocator());
    const initial_end = file.highlight_start + file.highlights.len;
    for ([_]u16{ 50, 12, 70 }) |rows| {
        p.update(.{ .resize = .{ .cols = 80, .rows = rows } });
        _ = frame.reset(.retain_capacity);
        const surface = try p.render(frame.allocator());
        const rect = p.rects[0];
        const body_y = if (p.settings.tag_bottom) rect.y else rect.y + pardes.BOX_H;
        var seen: usize = 0;
        for (body_y..body_y + rect.h - pardes.BOX_H) |y| {
            for (rect.x + config.GUTTER..rect.x + rect.w - 1) |x| {
                const first = surface.at(@intCast(x), @intCast(y));
                const second = surface.at(@intCast(x + 1), @intCast(y));
                if (!(std.mem.eql(u8, first.grapheme(), "f") and std.mem.eql(u8, second.grapheme(), "n")) and
                    !(std.mem.eql(u8, first.grapheme(), "i") and std.mem.eql(u8, second.grapheme(), "f"))) continue;
                seen += 1;
                for ([_]*pardes.Cell{ first, second }) |cell| {
                    try std.testing.expectEqual(pardes.Color{ .rgb = p.theme().kw }, cell.style.fg);
                    try std.testing.expect(cell.style.bold);
                }
            }
        }
        try std.testing.expect(seen >= 2 * (rows - 4));
        try std.testing.expect(file.highlight_start + file.highlights.len > initial_end);
        try std.testing.expect(!file.syntax_dirty);
    }
}

test "Zig keywords keep every rendered byte colored across line-number widths" {
    if (!syntax.enabled) return error.SkipZigTest;
    const gpa = std.testing.allocator;
    const samples = [_][]const u8{
        "pub fn main() void { if (true) {} }\n",
        "\tpub fn main() void { if (true) {} }\n",
        "const text = \"λ界\"; pub fn main() void { if (true) {} }\n",
    };
    for ([_]usize{ 9999, 10000, 99999, 100000 }) |line| {
        for (samples) |sample| {
            for ([_]struct { cols: u16, wrap: bool, horizontal: i32 }{
                .{ .cols = 96, .wrap = false, .horizontal = 0 },
                .{ .cols = 96, .wrap = false, .horizontal = 2 },
                .{ .cols = 38, .wrap = true, .horizontal = 0 },
            }) |view| {
                const source = try gpa.alloc(u8, line - 1 + sample.len);
                defer gpa.free(source);
                @memset(source[0 .. line - 1], '\n');
                @memcpy(source[line - 1 ..], sample);
                const p = try Pardes.init(gpa, .{ .tty_only = true, .cols = view.cols, .rows = 10 });
                defer p.deinit();
                const pane = try p.setTestFile(source);
                const file = &pane.file.?;
                gpa.free(file.path);
                file.path = try gpa.dupe(u8, "/highlight.zig");
                file.scroll = line - 1;
                pane.cur_row = @intCast(line - 1);
                pane.cur_col = @intCast(std.mem.indexOf(u8, sample, "fn").?);
                pane.hscroll = view.horizontal;
                p.settings.colors = true;
                p.settings.wrap = view.wrap;
                p.presentation.enabled = false;
                var frame = std.heap.ArenaAllocator.init(gpa);
                defer frame.deinit();
                const surface = try p.render(frame.allocator());
                var seen: usize = 0;
                var if_position: ?struct { x: u16, y: u16 } = null;
                const rect = p.rects[0];
                const body_y = if (p.settings.tag_bottom) rect.y else rect.y + pardes.BOX_H;
                for (body_y..body_y + rect.h - pardes.BOX_H) |y| {
                    for (rect.x + config.GUTTER..rect.x + rect.w - 1) |x| {
                        const first = surface.at(@intCast(x), @intCast(y));
                        const second = surface.at(@intCast(x + 1), @intCast(y));
                        const keyword = (std.mem.eql(u8, first.grapheme(), "f") and std.mem.eql(u8, second.grapheme(), "n")) or
                            (std.mem.eql(u8, first.grapheme(), "i") and std.mem.eql(u8, second.grapheme(), "f"));
                        if (!keyword) continue;
                        seen += 1;
                        if (std.mem.eql(u8, first.grapheme(), "f")) {
                            try std.testing.expectEqual(@as(u16, @intCast(x)), surface.cursor.?.x);
                            try std.testing.expectEqual(@as(u16, @intCast(y)), surface.cursor.?.y);
                        } else if_position = .{ .x = @intCast(x), .y = @intCast(y) };
                        for ([_]*pardes.Cell{ first, second }) |cell| {
                            const expected: pardes.Color = .{ .rgb = p.theme().kw };
                            if (!std.meta.eql(expected, cell.style.fg)) std.debug.print(
                                "\nline={d} wrap={} horizontal={d} sample={s} cell={s}\n",
                                .{ line, view.wrap, view.horizontal, sample, cell.grapheme() },
                            );
                            try std.testing.expectEqual(expected, cell.style.fg);
                            try std.testing.expect(!cell.style.bold);
                        }
                    }
                }
                try std.testing.expectEqual(@as(usize, 2), seen);
                const clicked = if_position.?;
                p.update(.{ .mouse = .{ .button = config.select_button, .kind = .press, .col = clicked.x, .row = clicked.y } });
                p.update(.{ .mouse = .{ .button = config.select_button, .kind = .release, .col = clicked.x, .row = clicked.y } });
                try std.testing.expectEqual(@as(i32, @intCast(line - 1)), pane.cur_row);
                try std.testing.expectEqual(@as(i32, @intCast(std.mem.indexOf(u8, sample, "if").?)), pane.cur_col);
            }
        }
    }
}

test "terminal overlays preserve trailing blank styles without coloring inserted rows" {
    if (comptime !panes.Terminal.enabled) return error.SkipZigTest;
    const gpa = std.testing.allocator;
    const p = try Pardes.init(gpa, .{ .tty_only = true, .cols = 40, .rows = 12 });
    defer p.deinit();
    while (p.nextEffect()) |_| {}
    const pane = p.panes[0].?;
    pane.tty_filter = false;
    p.update(.{ .output = .{ .pane = 0, .bytes = "A\r\n\x1b[41m\x1b[2K\r\n\x1b[42m\x1b[2K\r\n\x1b[44m\x1b[2K\x1b[0m" } });
    pane.mode = .normal;
    pane.ovl = .{ .row = 0, .rows = 3, .text = try gpa.dupe(u8, "A\n\n") };
    var frame = std.heap.ArenaAllocator.init(gpa);
    defer frame.deinit();
    const rect = p.rects[0];
    const x = rect.x + config.GUTTER;
    const y = if (p.settings.tag_bottom) rect.y else rect.y + pardes.BOX_H;
    const palette = p.theme().palette.?;
    const colors = [_]pardes.Color{ .{ .rgb = palette[1] }, .{ .rgb = palette[2] }, .{ .rgb = palette[4] } };
    const original = try p.render(frame.allocator());
    for (colors, 0..) |color, row| {
        const cell = original.at(x, y + 1 + @as(u16, @intCast(row)));
        try std.testing.expectEqualStrings(" ", cell.grapheme());
        try std.testing.expectEqual(color, cell.style.bg);
    }
    try std.testing.expect(p.shell_rows.pane == null);

    gpa.free(pane.ovl.?.text);
    pane.ovl.?.text = try gpa.dupe(u8, "A\n\n\n");
    _ = frame.reset(.retain_capacity);
    const extended = try p.render(frame.allocator());
    for (colors[0..2], 0..) |color, row|
        try std.testing.expectEqual(color, extended.at(x, y + 1 + @as(u16, @intCast(row))).style.bg);
    const inserted = extended.at(x, y + 3);
    try std.testing.expectEqualStrings(" ", inserted.grapheme());
    for (colors) |color| try std.testing.expect(!std.meta.eql(color, inserted.style.bg));
    try std.testing.expectEqual(colors[2], extended.at(x, y + 4).style.bg);
    try std.testing.expect(p.shell_rows.pane == null);
}