const std = @import("std");
const builtin = @import("builtin");

// scoped, not bare std.log: main.zig's logFn drops the unscoped .default scope
// wholesale (ghostty and uucode log there too), and a corrupt dump's parse
// diagnostic is the only thing that says WHICH field went bad.
const log = std.log.scoped(.dump);

/// Where the next dump goes. $PARDES_DUMP wins verbatim (the snapshot harness
/// pins it for deterministic goldens); else $XDG_DATA_HOME|~/.local/share
/// /pardes/pardes-<utc>.zon — timestamped so dumps never overwrite each other.
/// Creates the pardes dir (parents assumed; a failure surfaces at open).
pub fn outPath(buf: *[1024:0]u8) ?[:0]const u8 {
    if (std.c.getenv("PARDES_DUMP")) |p|
        return std.fmt.bufPrintSentinel(buf, "{s}", .{std.mem.span(p)}, 0) catch null;
    var dir_buf: [900]u8 = undefined;
    const dir = if (std.c.getenv("XDG_DATA_HOME")) |x|
        std.fmt.bufPrint(&dir_buf, "{s}/pardes", .{std.mem.span(x)}) catch return null
    else if (std.c.getenv("HOME")) |h|
        std.fmt.bufPrint(&dir_buf, "{s}/.local/share/pardes", .{std.mem.span(h)}) catch return null
    else
        return null;
    var dz: [901:0]u8 = undefined;
    @memcpy(dz[0..dir.len], dir);
    dz[dir.len] = 0;
    _ = std.c.mkdir(dz[0..dir.len :0], 0o755); // EEXIST is fine
    var ts: std.c.timespec = undefined;
    _ = std.c.clock_gettime(.REALTIME, &ts);
    const es: std.time.epoch.EpochSeconds = .{ .secs = @intCast(@max(0, ts.sec)) };
    const yd = es.getEpochDay().calculateYearDay();
    const md = yd.calculateMonthDay();
    const ds = es.getDaySeconds();
    return std.fmt.bufPrintSentinel(buf, "{s}/pardes-{d:0>4}{d:0>2}{d:0>2}-{d:0>2}{d:0>2}{d:0>2}.zon", .{
        dir,                    yd.year,                   md.month.numeric(),
        @as(u8, md.day_index) + 1, ds.getHoursIntoDay(),   ds.getMinutesIntoHour(),
        ds.getSecondsIntoMinute(),
    }, 0) catch null;
}
pub const magic = "pardes-dump";
pub const version: u32 = 1;
pub const max_panes: usize = 16;
pub const max_cols: usize = 6;

pub const Size = struct {
    cols: u16,
    rows: u16,
};

pub const Cursor = struct {
    col: u16 = 0,
    row: u16 = 0,
};

pub const PaneKind = enum {
    terminal,
    file,
    image,
};

pub const Terminal = struct {
    cwd: []const u8 = "",
    stream: []const u8 = "",
    stream_b64: []const u8 = "",
    cursor: Cursor = .{},
};

pub const File = struct {
    path: []const u8 = "",
    content: []const u8 = "",
    content_b64: []const u8 = "",
    /// an output buffer (no file behind the name) — see pardes.File.output
    output: bool = false,
};

pub const Image = struct {
    path: []const u8 = "",
    bytes_b64: []const u8 = "",
};

pub const Pane = struct {
    kind: PaneKind,
    tag: []const u8,
    body: []const u8,
    scroll: usize = 0,
    cols: u16 = 0,
    rows: u16 = 0,
    vweight: f32 = 1,
    terminal: ?Terminal = null,
    file: ?File = null,
    image: ?Image = null,
};

pub const Column = struct {
    weight: f32 = 1,
    panes: []const usize = &.{},
};

pub const State = struct {
    magic: []const u8 = magic,
    version: u32 = version,
    screen: Size,
    active: usize = 0,
    topbar: []const u8 = "",
    theme: []const u8 = "dark",
    columns: []const Column = &.{},
    panes: []const Pane = &.{},
};

pub fn validate(state: State) !void {
    if (!std.mem.eql(u8, state.magic, magic)) return error.BadDumpMagic;
    if (state.version != version) return error.BadDumpVersion;
    if (state.panes.len == 0 or state.panes.len > max_panes) return error.BadDumpPanes;
    if (state.columns.len == 0 or state.columns.len > max_cols) return error.BadDumpColumns;
    if (state.active >= state.panes.len) return error.BadDumpActive;
    for (state.columns) |col| {
        if (col.panes.len == 0 or col.panes.len > max_panes) return error.BadDumpColumns;
        for (col.panes) |pane| {
            if (pane >= state.panes.len) return error.BadDumpPaneRef;
        }
    }
    for (state.panes) |pane| {
        switch (pane.kind) {
            .terminal => if (pane.terminal == null) return error.BadDumpPaneKind,
            .file => if (pane.file == null) return error.BadDumpPaneKind,
            .image => if (pane.image == null) return error.BadDumpPaneKind,
        }
    }
}

pub fn writeFile(io: std.Io, gpa: std.mem.Allocator, path: []const u8, state: State) !void {
    try validate(state);
    var out: std.Io.Writer.Allocating = .init(gpa);
    defer out.deinit();
    try std.zon.stringify.serialize(state, .{ .whitespace = true }, &out.writer);

    var file = try std.Io.Dir.createFileAbsolute(io, path, .{});
    defer file.close(io);
    try file.writeStreamingAll(io, out.written());
}

pub fn readFile(io: std.Io, gpa: std.mem.Allocator, path: []const u8) !State {
    const bytes = try std.Io.Dir.cwd().readFileAlloc(io, path, gpa, .limited(64 * 1024 * 1024));
    defer gpa.free(bytes);
    return readZon(gpa, bytes, path);
}

pub fn readZon(gpa: std.mem.Allocator, bytes: []const u8, label: []const u8) !State {
    const source = try gpa.dupeZ(u8, bytes);
    defer gpa.free(source);
    return readZonZ(gpa, source, label);
}

pub fn readZonZ(gpa: std.mem.Allocator, source: [:0]const u8, label: []const u8) !State {
    if (builtin.os.tag == .emscripten) {
        const state = std.zon.parse.fromSliceAlloc(State, gpa, source, null, .{}) catch |err| {
            log.err("parse dump {s}: {s}", .{ label, @errorName(err) });
            return err;
        };
        errdefer std.zon.parse.free(gpa, state);
        try validate(state);
        return state;
    }

    var diag: std.zon.parse.Diagnostics = .{};
    defer diag.deinit(gpa);
    const state = std.zon.parse.fromSliceAlloc(State, gpa, source, &diag, .{}) catch |err| {
        log.err("parse dump {s}: {f}", .{ label, diag });
        return err;
    };
    errdefer std.zon.parse.free(gpa, state);
    try validate(state);
    return state;
}

pub fn free(gpa: std.mem.Allocator, state: State) void {
    std.zon.parse.free(gpa, state);
}

pub fn encodeBytes(alloc: std.mem.Allocator, bytes: []const u8) ![]const u8 {
    const enc = std.base64.standard.Encoder;
    const out = try alloc.alloc(u8, enc.calcSize(bytes.len));
    return enc.encode(out, bytes);
}

pub fn decodeBytes(alloc: std.mem.Allocator, b64: []const u8) ![]u8 {
    const dec = std.base64.standard.Decoder;
    const n = try dec.calcSizeForSlice(b64);
    const out = try alloc.alloc(u8, n);
    errdefer alloc.free(out);
    try dec.decode(out, b64);
    return out;
}

test "dump zon roundtrip" {
    const gpa = std.testing.allocator;
    const tty_b64 = try encodeBytes(gpa, "old\nhello\nworld");
    defer gpa.free(tty_b64);
    const file_b64 = try encodeBytes(gpa, "alpha\nbeta\n");
    defer gpa.free(file_b64);
    const panes = [_]Pane{
        .{
            .kind = .terminal,
            .tag = "nm /tmp Del",
            .body = "hello\nworld",
            .scroll = 1,
            .cols = 40,
            .rows = 10,
            .terminal = .{ .cwd = "/tmp", .stream = "old\nhello\nworld", .stream_b64 = tty_b64, .cursor = .{ .col = 3, .row = 2 } },
        },
        .{
            .kind = .file,
            .tag = "nm /tmp/a.txt Save Del",
            .body = "   1 alpha",
            .cols = 20,
            .rows = 5,
            .file = .{ .path = "/tmp/a.txt", .content = "alpha\nbeta\n", .content_b64 = file_b64 },
        },
    };
    const col_panes = [_]usize{ 0, 1 };
    const columns = [_]Column{.{ .weight = 1, .panes = &col_panes }};
    const state: State = .{
        .screen = .{ .cols = 80, .rows = 24 },
        .topbar = "Kill Newcol Dump",
        .theme = "dark",
        .columns = &columns,
        .panes = &panes,
    };

    var out: std.Io.Writer.Allocating = .init(gpa);
    defer out.deinit();
    try std.zon.stringify.serialize(state, .{ .whitespace = true }, &out.writer);
    const source = try out.toOwnedSliceSentinel(0);
    defer gpa.free(source);

    var diag: std.zon.parse.Diagnostics = .{};
    defer diag.deinit(gpa);
    const parsed = try std.zon.parse.fromSliceAlloc(State, gpa, source, &diag, .{});
    defer std.zon.parse.free(gpa, parsed);
    try validate(parsed);
    try std.testing.expectEqual(@as(usize, 2), parsed.panes.len);
    try std.testing.expectEqualStrings("dark", parsed.theme);
    try std.testing.expectEqualStrings("old\nhello\nworld", parsed.panes[0].terminal.?.stream);
    try std.testing.expectEqualStrings("alpha\nbeta\n", parsed.panes[1].file.?.content);
    {
        const bytes = try decodeBytes(gpa, parsed.panes[0].terminal.?.stream_b64);
        defer gpa.free(bytes);
        try std.testing.expectEqualStrings("old\nhello\nworld", bytes);
    }
    {
        const bytes = try decodeBytes(gpa, parsed.panes[1].file.?.content_b64);
        defer gpa.free(bytes);
        try std.testing.expectEqualStrings("alpha\nbeta\n", bytes);
    }
}