path: root/test/snapshot.zig

// pardes-snap: drive a pardes binary with a scripted input trace in a pty and
// capture the rendered grid at named sync points. The same script run against
// the prototype and the rewrite must produce byte-identical captures — this is
// the old-vs-new parity oracle for the rewrite.
//
//   zig build snap                        run all snapshots/*.snap, diff goldens
//   zig build snap -- --update            regenerate goldens from this binary
//   zig build snap -- snapshots/boot.snap one script
//
// Script commands (line-oriented, # comments):
//   file <name> <content>     create file in the script's cwd (before start)
//   lines <name> <n>          create file with n numbered lines
//   dirmk <name>              create a subdirectory
//   start <rows> <cols> [arg] fork the app in a pty (optional extra CLI arg)
//   wait <ms> <needle...>     pump until needle appears on the grid (fails hard)
//   settle <ms>               pump for a fixed duration
//   stable <quiet_ms> <timeout_ms>  pump until the grid stops changing
//   text <literal>            send literal bytes
//   send <escaped>            send with \e \r \n \t \\ \xNN escapes
//   key <names...>            enter esc tab bs space up down left right home end
//                             pgup pgdn c-<ch> a-<ch>   (after esc: settle >=600ms,
//                             or vaxis parses the next byte as alt-<ch>)
//   press|release <left|middle|right> <col> <row>   SGR mouse, 1-based
//   drag <btn> <col> <row>    motion with button held
//   motion <col> <row>        button-less motion (hover)
//   wheel <up|down> <col> <row>
//   resize <rows> <cols>
//   snap <label>              capture grid text + cursor
//   snapstyle <label>         capture per-cell style runs (fg,bg,attrs)
const std = @import("std");
const posix = std.posix;
const linux = std.os.linux;
const ghostty_vt = @import("ghostty-vt");
const eh = @import("e2e_harness.zig");

extern "c" fn setenv(name: [*:0]const u8, value: [*:0]const u8, overwrite: c_int) c_int;
extern "c" fn execvp(file: [*:0]const u8, argv: [*:null]const ?[*:0]const u8) c_int;

const SNAP_BASE = "/tmp/pardes-snap";
const gpa = std.heap.page_allocator;

pub fn main(init: std.process.Init) !void {
    var arena_state = std.heap.ArenaAllocator.init(gpa);
    defer arena_state.deinit();
    const arena = arena_state.allocator();
    const args = try init.minimal.args.toSlice(init.arena.allocator());

    // argv: exe-under-test, then flags/scripts. All paths made absolute up
    // front because runScript chdirs into a per-script workdir.
    var cwd_buf: [4096]u8 = undefined;
    const cwd_rc: isize = @bitCast(linux.getcwd(&cwd_buf, cwd_buf.len));
    if (cwd_rc <= 0) fatal("getcwd failed", .{});
    const orig_cwd = cwd_buf[0..@intCast(cwd_rc - 1)];

    var exe: ?[]const u8 = null;
    var update = false;
    var scripts: std.ArrayList([]const u8) = .empty;
    for (args[1..]) |a| {
        if (std.mem.eql(u8, a, "--update")) {
            update = true;
        } else if (exe == null) {
            exe = try absPath(arena, orig_cwd, a);
        } else {
            try scripts.append(arena, try absPath(arena, orig_cwd, a));
        }
    }
    if (exe == null) fatal("usage: pardes-snap <exe> [scripts...] [--update]", .{});
    const exe_z = try arena.dupeZ(u8, exe.?);

    if (scripts.items.len == 0) {
        try listSnaps(arena, try absPath(arena, orig_cwd, "test/snapshots"), &scripts);
        std.mem.sort([]const u8, scripts.items, {}, struct {
            fn lt(_: void, x: []const u8, y: []const u8) bool {
                return std.mem.lessThan(u8, x, y);
            }
        }.lt);
    }
    if (scripts.items.len == 0) fatal("no .snap scripts found", .{});

    var failed: usize = 0;
    for (scripts.items) |script_path| {
        const stem = std.fs.path.stem(script_path);
        const base_path = script_path[0 .. script_path.len - ".snap".len];
        const golden_path = try std.fmt.allocPrint(arena, "{s}.golden", .{base_path});
        const out = runScript(arena, exe_z, script_path, stem) catch |e| {
            std.debug.print("FAIL {s}: script error {s}\n", .{ stem, @errorName(e) });
            failed += 1;
            continue;
        };
        if (update) {
            try eh.writeFile(try arena.dupeZ(u8, golden_path), out);
            std.debug.print("UPDATED {s} ({d} bytes)\n", .{ stem, out.len });
        } else {
            const golden = readFileAlloc(arena, golden_path) catch {
                std.debug.print("FAIL {s}: no golden (run with -- --update)\n", .{stem});
                failed += 1;
                continue;
            };
            if (std.mem.eql(u8, golden, out)) {
                std.debug.print("PASS {s}\n", .{stem});
            } else {
                const actual_path = try std.fmt.allocPrint(arena, "{s}.actual", .{base_path});
                try eh.writeFile(try arena.dupeZ(u8, actual_path), out);
                std.debug.print("FAIL {s}: differs from golden (actual written to {s})\n", .{ stem, actual_path });
                printFirstDiff(golden, out);
                failed += 1;
            }
        }
    }
    if (failed > 0) {
        std.debug.print("{d}/{d} snapshot scripts FAILED\n", .{ failed, scripts.items.len });
        std.process.exit(1);
    }
    std.debug.print("all {d} snapshot scripts ok\n", .{scripts.items.len});
}

fn runScript(arena: std.mem.Allocator, exe_z: [:0]const u8, script_path: []const u8, stem: []const u8) ![]u8 {
    const src = try readFileAlloc(arena, script_path);

    // Fixed, recreated-per-run workdir: its PATH shows up in pane tags, so it
    // must be identical across runs and across old/new binaries.
    const base = try std.fmt.allocPrint(arena, "{s}/{s}", .{ SNAP_BASE, stem });
    rmrf(base);
    try mkdir(arena, SNAP_BASE, true);
    try mkdir(arena, base, false);
    const home = try std.fmt.allocPrint(arena, "{s}/home", .{base});
    const work = try std.fmt.allocPrint(arena, "{s}/cwd", .{base});
    try mkdir(arena, home, false);
    try mkdir(arena, work, false);
    // deterministic shell: fixed prompt, no history, no user rc leakage
    try eh.writeFile(try std.fmt.allocPrintSentinel(arena, "{s}/.bashrc", .{home}, 0), "PS1='$ '\nHISTFILE=\n");
    _ = setenv("HOME", try arena.dupeZ(u8, home), 1);
    _ = setenv("TERM", "xterm-256color", 1);
    _ = setenv("LC_ALL", "C", 1);
    if (chdirRc(try arena.dupeZ(u8, work)) < 0) return error.ChdirFailed;

    var out: std.ArrayList(u8) = .empty;
    var h: ?eh.Harness = null;
    defer if (h) |*hp| hp.deinit();

    var lines_it = std.mem.splitScalar(u8, src, '\n');
    var lineno: usize = 0;
    while (lines_it.next()) |raw_line| {
        lineno += 1;
        const line = std.mem.trim(u8, raw_line, " \t\r");
        if (line.len == 0 or line[0] == '#') continue;
        var tok = std.mem.tokenizeScalar(u8, line, ' ');
        const cmd = tok.next().?;
        errdefer std.debug.print("  at {s}:{d}: {s}\n", .{ script_path, lineno, line });

        if (std.mem.eql(u8, cmd, "file")) {
            const name = tok.next() orelse return error.BadScript;
            try eh.writeFile(try arena.dupeZ(u8, name), try unescape(arena, tok.rest()));
        } else if (std.mem.eql(u8, cmd, "lines")) {
            const name = tok.next() orelse return error.BadScript;
            const n = try std.fmt.parseInt(usize, tok.next() orelse return error.BadScript, 10);
            var buf: std.ArrayList(u8) = .empty;
            for (1..n + 1) |i| try buf.appendSlice(arena, try std.fmt.allocPrint(arena, "line {d}\n", .{i}));
            try eh.writeFile(try arena.dupeZ(u8, name), buf.items);
        } else if (std.mem.eql(u8, cmd, "ppmdiag")) {
            // the 64x64 diagonal-split test PPM (white/blue) from the old e2e
            const name = tok.next() orelse return error.BadScript;
            var ppm: std.ArrayList(u8) = .empty;
            try ppm.appendSlice(arena, "P6\n64 64\n255\n");
            var py: usize = 0;
            while (py < 64) : (py += 1) {
                var px: usize = 0;
                while (px < 64) : (px += 1)
                    try ppm.appendSlice(arena, if (px + py < 64) &[_]u8{ 255, 255, 255 } else &[_]u8{ 0, 0, 255 });
            }
            try eh.writeFile(try arena.dupeZ(u8, name), ppm.items);
        } else if (std.mem.eql(u8, cmd, "dirmk")) {
            try mkdir(arena, tok.next() orelse return error.BadScript, false);
        } else if (std.mem.eql(u8, cmd, "start")) {
            const rows = try std.fmt.parseInt(u16, tok.next() orelse return error.BadScript, 10);
            const cols = try std.fmt.parseInt(u16, tok.next() orelse return error.BadScript, 10);
            var extra: [6]?[*:0]const u8 = @splat(null);
            var nextra: usize = 0;
            while (tok.next()) |a| : (nextra += 1) {
                if (nextra >= extra.len) return error.BadScript;
                extra[nextra] = (try arena.dupeZ(u8, a)).ptr;
            }
            if (h) |*hp| hp.deinit(); // scripts may restart (e.g. dump then -l)
            h = try eh.Harness.initArgv(gpa, exe_z.ptr, rows, cols, extra[0..nextra]);
        } else if (std.mem.eql(u8, cmd, "snapfile")) {
            const label = tok.next() orelse return error.BadScript;
            const contents = try readFileAlloc(arena, tok.rest());
            try out.appendSlice(arena, try std.fmt.allocPrint(arena, "== file {s}\n", .{label}));
            // elide base64 payloads: they encode raw pty byte HISTORY, whose
            // micro-timing (prompt redraw cycles) legitimately differs between
            // implementations; the cleaned text fields are the contract.
            var flines = std.mem.splitScalar(u8, contents, '\n');
            while (flines.next()) |fl| {
                if (std.mem.indexOf(u8, fl, "_b64 = \"") != null) {
                    const eq = std.mem.indexOf(u8, fl, "=").?;
                    try out.appendSlice(arena, fl[0 .. eq + 1]);
                    try out.appendSlice(arena, " <elided>\n");
                } else {
                    try out.appendSlice(arena, fl);
                    try out.append(arena, '\n');
                }
            }
            try out.appendSlice(arena, "== end file\n");
        } else if (std.mem.eql(u8, cmd, "wait")) {
            const ms = try std.fmt.parseInt(i64, tok.next() orelse return error.BadScript, 10);
            try live(&h).expectWaitFor(tok.rest(), ms, "snapshot wait");
        } else if (std.mem.eql(u8, cmd, "settle")) {
            try live(&h).pump(try std.fmt.parseInt(i64, tok.next() orelse return error.BadScript, 10));
        } else if (std.mem.eql(u8, cmd, "stable")) {
            const quiet = try std.fmt.parseInt(i64, tok.next() orelse return error.BadScript, 10);
            const timeout = try std.fmt.parseInt(i64, tok.next() orelse return error.BadScript, 10);
            try waitStable(live(&h), quiet, timeout);
        } else if (std.mem.eql(u8, cmd, "text")) {
            try live(&h).send(tok.rest());
        } else if (std.mem.eql(u8, cmd, "send")) {
            try live(&h).send(try unescape(arena, tok.rest()));
        } else if (std.mem.eql(u8, cmd, "key")) {
            while (tok.next()) |name| try live(&h).send(keyBytes(name) orelse return error.BadKey);
        } else if (std.mem.eql(u8, cmd, "press") or std.mem.eql(u8, cmd, "release") or std.mem.eql(u8, cmd, "drag")) {
            const btn = buttonCode(tok.next() orelse return error.BadScript) orelse return error.BadScript;
            const col = try std.fmt.parseInt(u16, tok.next() orelse return error.BadScript, 10);
            const row = try std.fmt.parseInt(u16, tok.next() orelse return error.BadScript, 10);
            const b: u16 = if (std.mem.eql(u8, cmd, "drag")) btn + 32 else btn;
            const fin: u8 = if (std.mem.eql(u8, cmd, "release")) 'm' else 'M';
            try live(&h).send(try std.fmt.allocPrint(arena, "\x1b[<{d};{d};{d}{c}", .{ b, col, row, fin }));
        } else if (std.mem.eql(u8, cmd, "motion")) {
            const col = try std.fmt.parseInt(u16, tok.next() orelse return error.BadScript, 10);
            const row = try std.fmt.parseInt(u16, tok.next() orelse return error.BadScript, 10);
            try live(&h).send(try std.fmt.allocPrint(arena, "\x1b[<35;{d};{d}M", .{ col, row }));
        } else if (std.mem.eql(u8, cmd, "wheel")) {
            const dir = tok.next() orelse return error.BadScript;
            const b: u16 = if (std.mem.eql(u8, dir, "up")) 64 else 65;
            const col = try std.fmt.parseInt(u16, tok.next() orelse return error.BadScript, 10);
            const row = try std.fmt.parseInt(u16, tok.next() orelse return error.BadScript, 10);
            try live(&h).send(try std.fmt.allocPrint(arena, "\x1b[<{d};{d};{d}M", .{ b, col, row }));
        } else if (std.mem.eql(u8, cmd, "resize")) {
            const rows = try std.fmt.parseInt(u16, tok.next() orelse return error.BadScript, 10);
            const cols = try std.fmt.parseInt(u16, tok.next() orelse return error.BadScript, 10);
            try live(&h).resize(rows, cols);
        } else if (std.mem.eql(u8, cmd, "snap")) {
            try snapText(arena, &out, live(&h), tok.rest());
        } else if (std.mem.eql(u8, cmd, "snapstyle")) {
            try snapStyle(arena, &out, live(&h), tok.rest());
        } else {
            std.debug.print("unknown command {s}\n", .{cmd});
            return error.BadScript;
        }
    }
    return out.items;
}

fn live(h: *?eh.Harness) *eh.Harness {
    if (h.*) |*v| return v;
    fatal("script used the app before `start`", .{});
}

/// Pump until the grid is unchanged for `quiet` ms (bounded by `timeout`).
/// The one sync primitive that needs no needle — used before every snap so
/// old and new binaries are compared at rest, not mid-repaint.
fn waitStable(h: *eh.Harness, quiet: i64, timeout: i64) !void {
    var total: i64 = 0;
    var prev = try h.screenText();
    defer h.gpa.free(prev);
    while (total < timeout) {
        try h.pump(quiet);
        total += quiet;
        const cur = try h.screenText();
        if (std.mem.eql(u8, prev, cur)) {
            h.gpa.free(cur);
            return;
        }
        h.gpa.free(prev);
        prev = cur;
    }
    return error.NeverStable;
}

fn snapText(arena: std.mem.Allocator, out: *std.ArrayList(u8), h: *eh.Harness, label: []const u8) !void {
    const text = try h.screenText();
    defer h.gpa.free(text);
    const c = h.cursor();
    try out.appendSlice(arena, try std.fmt.allocPrint(arena, "== snap {s} grid={d}x{d} cursor={d},{d}\n", .{ label, h.cols, h.rows, c.x, c.y }));
    var it = std.mem.splitScalar(u8, text, '\n');
    var row: usize = 0;
    while (row < h.rows) : (row += 1) {
        const line = it.next() orelse "";
        try out.append(arena, '|');
        try out.appendSlice(arena, std.mem.trimEnd(u8, line, " "));
        try out.append(arena, '\n');
    }
}

/// Per-row style runs from the harness emulator: `|y: x0-x1 fg,bg,attrs ...`.
/// fg/bg: d (default) | pN (palette) | #rrggbb. attrs: b f i k r v x + u U ~ . -
/// for underline single/double/curly/dotted/dashed.
fn snapStyle(arena: std.mem.Allocator, out: *std.ArrayList(u8), h: *eh.Harness, label: []const u8) !void {
    try out.appendSlice(arena, try std.fmt.allocPrint(arena, "== style {s}\n", .{label}));
    var y: u16 = 0;
    while (y < h.rows) : (y += 1) {
        try out.appendSlice(arena, try std.fmt.allocPrint(arena, "|{d}:", .{y}));
        var run_buf: [64]u8 = undefined;
        var key_buf: [64]u8 = undefined;
        var run_key: []const u8 = "";
        var run_start: u16 = 0;
        var x: u16 = 0;
        while (x <= h.cols) : (x += 1) {
            const key: []const u8 = if (x == h.cols) "\x00end" else cellKey(h, x, y, &key_buf);
            if (x == 0) {
                run_key = try arena.dupe(u8, key);
                continue;
            }
            if (std.mem.eql(u8, key, run_key)) continue;
            try out.appendSlice(arena, try std.fmt.bufPrint(&run_buf, " {d}-{d} ", .{ run_start, x - 1 }));
            try out.appendSlice(arena, run_key);
            run_key = try arena.dupe(u8, key);
            run_start = x;
        }
        try out.append(arena, '\n');
    }
}

fn cellKey(h: *eh.Harness, x: u16, y: u16, buf: *[64]u8) []const u8 {
    const ci = h.term.screens.active.pages.getCell(.{ .viewport = .{ .x = x, .y = y } }) orelse return "d,d,";
    if (ci.cell.wide == .spacer_tail) return "d,d,";
    const style = ci.style();
    var n: usize = 0;
    var tmp: [16]u8 = undefined;
    const fg = colorStr(style.fg_color, &tmp);
    @memcpy(buf[n..][0..fg.len], fg);
    n += fg.len;
    buf[n] = ',';
    n += 1;
    var tmp2: [16]u8 = undefined;
    const bg: []const u8 = switch (ci.cell.content_tag) {
        .bg_color_palette => std.fmt.bufPrint(&tmp2, "p{d}", .{ci.cell.content.color_palette.data}) catch "?",
        .bg_color_rgb => blk: {
            const rgb = ci.cell.content.color_rgb;
            break :blk std.fmt.bufPrint(&tmp2, "#{x:0>2}{x:0>2}{x:0>2}", .{ rgb.r, rgb.g, rgb.b }) catch "?";
        },
        else => colorStr(style.bg_color, &tmp2),
    };
    @memcpy(buf[n..][0..bg.len], bg);
    n += bg.len;
    buf[n] = ',';
    n += 1;
    if (style.flags.bold) {
        buf[n] = 'b';
        n += 1;
    }
    if (style.flags.faint) {
        buf[n] = 'f';
        n += 1;
    }
    if (style.flags.italic) {
        buf[n] = 'i';
        n += 1;
    }
    if (style.flags.blink) {
        buf[n] = 'k';
        n += 1;
    }
    if (style.flags.inverse) {
        buf[n] = 'r';
        n += 1;
    }
    if (style.flags.invisible) {
        buf[n] = 'v';
        n += 1;
    }
    if (style.flags.strikethrough) {
        buf[n] = 'x';
        n += 1;
    }
    const ul: []const u8 = switch (style.flags.underline) {
        .none => "",
        .single => "u",
        .double => "U",
        .curly => "~",
        .dotted => ".",
        .dashed => "-",
    };
    @memcpy(buf[n..][0..ul.len], ul);
    n += ul.len;
    return buf[0..n];
}

fn colorStr(color: ghostty_vt.Style.Color, buf: *[16]u8) []const u8 {
    return switch (color) {
        .none => "d",
        .palette => |idx| std.fmt.bufPrint(buf, "p{d}", .{idx}) catch "?",
        .rgb => |rgb| std.fmt.bufPrint(buf, "#{x:0>2}{x:0>2}{x:0>2}", .{ rgb.r, rgb.g, rgb.b }) catch "?",
    };
}

fn keyBytes(name: []const u8) ?[]const u8 {
    const map = .{
        .{ "enter", "\r" },    .{ "esc", "\x1b" },     .{ "tab", "\t" },
        .{ "bs", "\x7f" },     .{ "space", " " },      .{ "up", "\x1b[A" },
        .{ "down", "\x1b[B" }, .{ "right", "\x1b[C" }, .{ "left", "\x1b[D" },
        .{ "home", "\x1b[H" }, .{ "end", "\x1b[F" },   .{ "pgup", "\x1b[5~" },
        .{ "pgdn", "\x1b[6~" },
    };
    inline for (map) |e| if (std.mem.eql(u8, name, e[0])) return e[1];
    const S = struct {
        var buf: [2]u8 = undefined;
    };
    if (name.len == 1) {
        S.buf[0] = name[0];
        return S.buf[0..1];
    }
    if (name.len == 3 and name[1] == '-') {
        if (name[0] == 'c' and name[2] >= 'a' and name[2] <= 'z') {
            S.buf[0] = name[2] - 'a' + 1;
            return S.buf[0..1];
        }
        if (name[0] == 'a') {
            S.buf = .{ 0x1b, name[2] };
            return S.buf[0..2];
        }
    }
    return null;
}

fn buttonCode(name: []const u8) ?u16 {
    if (std.mem.eql(u8, name, "left")) return 0;
    if (std.mem.eql(u8, name, "middle")) return 1;
    if (std.mem.eql(u8, name, "right")) return 2;
    return null;
}

fn unescape(arena: std.mem.Allocator, s: []const u8) ![]const u8 {
    var buf: std.ArrayList(u8) = .empty;
    var i: usize = 0;
    while (i < s.len) : (i += 1) {
        if (s[i] != '\\' or i + 1 >= s.len) {
            try buf.append(arena, s[i]);
            continue;
        }
        i += 1;
        switch (s[i]) {
            'e' => try buf.append(arena, 0x1b),
            'r' => try buf.append(arena, '\r'),
            'n' => try buf.append(arena, '\n'),
            't' => try buf.append(arena, '\t'),
            '\\' => try buf.append(arena, '\\'),
            'x' => {
                if (i + 2 >= s.len) return error.BadEscape;
                try buf.append(arena, try std.fmt.parseInt(u8, s[i + 1 .. i + 3], 16));
                i += 2;
            },
            else => return error.BadEscape,
        }
    }
    return buf.items;
}

fn absPath(arena: std.mem.Allocator, cwd: []const u8, p: []const u8) ![]const u8 {
    if (p.len > 0 and p[0] == '/') return try arena.dupe(u8, p);
    return try std.fmt.allocPrint(arena, "{s}/{s}", .{ cwd, p });
}

fn listSnaps(arena: std.mem.Allocator, dir_path: []const u8, scripts: *std.ArrayList([]const u8)) !void {
    const dir_z = try arena.dupeZ(u8, dir_path);
    const rc = linux.open(dir_z, .{ .ACCMODE = .RDONLY, .DIRECTORY = true }, 0);
    const sfd: isize = @bitCast(rc);
    if (sfd < 0) fatal("no snapshots/ dir at {s}", .{dir_path});
    const fd: i32 = @intCast(sfd);
    defer _ = linux.close(fd);
    var buf: [8192]u8 align(@alignOf(linux.dirent64)) = undefined;
    while (true) {
        const r = linux.getdents64(fd, &buf, buf.len);
        const n: isize = @bitCast(r);
        if (n <= 0) break;
        var off: usize = 0;
        while (off < @as(usize, @intCast(n))) {
            const d: *align(1) linux.dirent64 = @ptrCast(&buf[off]);
            const name = std.mem.span(@as([*:0]const u8, @ptrCast(&d.name)));
            if (std.mem.endsWith(u8, name, ".snap"))
                try scripts.append(arena, try std.fmt.allocPrint(arena, "{s}/{s}", .{ dir_path, name }));
            off += d.reclen;
        }
    }
}

fn readFileAlloc(arena: std.mem.Allocator, path: []const u8) ![]u8 {
    const path_z = try arena.dupeZ(u8, path);
    const rc = linux.open(path_z, .{ .ACCMODE = .RDONLY }, 0);
    const sfd: isize = @bitCast(rc);
    if (sfd < 0) return error.OpenFailed;
    const fd: i32 = @intCast(sfd);
    defer _ = linux.close(fd);
    var buf: std.ArrayList(u8) = .empty;
    var chunk: [16384]u8 = undefined;
    while (true) {
        const r = linux.read(fd, &chunk, chunk.len);
        const n: isize = @bitCast(r);
        if (n < 0) {
            if (n == -@as(isize, @intFromEnum(linux.E.INTR))) continue;
            return error.ReadFailed;
        }
        if (n == 0) break;
        try buf.appendSlice(arena, chunk[0..@intCast(n)]);
    }
    return buf.items;
}

fn mkdir(arena: std.mem.Allocator, path: []const u8, exist_ok: bool) !void {
    const path_z = try arena.dupeZ(u8, path);
    const n: isize = @bitCast(linux.mkdir(path_z, 0o755));
    if (n < 0) {
        if (exist_ok and n == -@as(isize, @intFromEnum(linux.E.EXIST))) return;
        return error.MkdirFailed;
    }
}

fn chdirRc(path_z: [:0]const u8) isize {
    return @bitCast(linux.chdir(path_z.ptr));
}

fn rmrf(path: []const u8) void {
    var path_buf: [4096:0]u8 = undefined;
    if (path.len >= path_buf.len) return;
    @memcpy(path_buf[0..path.len], path);
    path_buf[path.len] = 0;
    const pid: isize = @bitCast(linux.fork());
    if (pid == 0) {
        const argv: [4:null]?[*:0]const u8 = .{ "rm", "-rf", @as([*:0]const u8, @ptrCast(&path_buf)), null };
        _ = execvp("rm", &argv);
        linux.exit_group(127);
    }
    if (pid < 0) return;
    var status: u32 = 0;
    _ = linux.wait4(@intCast(pid), &status, 0, null);
}

fn printFirstDiff(golden: []const u8, actual: []const u8) void {
    var gi = std.mem.splitScalar(u8, golden, '\n');
    var ai = std.mem.splitScalar(u8, actual, '\n');
    var n: usize = 1;
    while (true) : (n += 1) {
        const g = gi.next();
        const a = ai.next();
        if (g == null and a == null) return;
        if (g != null and a != null and std.mem.eql(u8, g.?, a.?)) continue;
        std.debug.print("  first diff at golden line {d}:\n  -{s}\n  +{s}\n", .{ n, g orelse "<eof>", a orelse "<eof>" });
        return;
    }
}

fn fatal(comptime fmt: []const u8, args: anytype) noreturn {
    std.debug.print(fmt ++ "\n", args);
    std.process.exit(1);
}