const std = @import("std");
const posix = std.posix;
const libc = std.c;
const ghostty_vt = @import("ghostty-vt");

// TIOCSWINSZ: absent from std.c.T on darwin — _IOW('t', 103, winsize)
const TIOCSWINSZ: c_int = @bitCast(@as(u32, if (@hasDecl(posix.T, "IOCSWINSZ")) posix.T.IOCSWINSZ else 0x80087467));

extern "c" fn forkpty(
    amaster: *c_int,
    name: ?[*:0]u8,
    termp: ?*const anyopaque,
    winp: ?*const posix.winsize,
) c_int;
extern "c" fn execvp(file: [*:0]const u8, argv: [*:null]const ?[*:0]const u8) c_int;
extern "c" fn _exit(status: c_int) noreturn;
extern "c" fn unsetenv(name: [*:0]const u8) c_int;

/// Monotonic milliseconds; the harness's only clock (std.time lost
/// milliTimestamp in 0.16).
pub fn nowMs() i64 {
    var ts: libc.timespec = undefined;
    _ = libc.clock_gettime(.MONOTONIC, &ts);
    return @as(i64, @intCast(ts.sec)) * 1000 + @divFloor(@as(i64, @intCast(ts.nsec)), 1_000_000);
}
const raw_capture_max = 64 * 1024 * 1024;

pub const RawCapture = struct {
    bytes: [raw_capture_max]u8 = undefined,
    items: []u8 = &.{},
    full: bool = false,

    fn appendSlice(self: *RawCapture, chunk: []const u8) error{CaptureFull}!void {
        if (self.full) return error.CaptureFull;
        if (chunk.len > self.bytes.len - self.items.len) {
            self.full = true;
            return error.CaptureFull;
        }
        const end = self.items.len + chunk.len;
        @memcpy(self.bytes[self.items.len..end], chunk);
        self.items = self.bytes[0..end];
    }
};

/// E2E test harness: forks the app in a pty and parses its output with a
/// ghostty terminal emulator. Tests read the 2D screen GRID (via plainString),
/// not raw byte streams — so they're decoupled from how the app renders
/// (vaxis diff-rendering, repaints, etc). The grid is always current after
/// `pump`/`waitFor`; no setWinsize-to-force-repaint hacks needed.
///
/// Input is sent as raw bytes to the pty (the app's vaxis parses them). The
/// harness terminal only reads output.
pub const Harness = struct {
    gpa: std.mem.Allocator,
    master: c_int,
    pid: posix.pid_t,
    /// heap-allocated so its address is stable: vtStream()'s handler holds a
    /// pointer back into the Terminal, so it must not move (same reason main.zig
    /// heap-allocates Term). Freed in deinit.
    term: *ghostty_vt.Terminal,
    stream: ghostty_vt.TerminalStream,
    rows: u16,
    cols: u16,
    /// when true, print the captured screen state after each pump/waitFor and on
    /// every assertion, so live test runs can be inspected (zig build test -Dtrace).
    trace: bool = false,
    /// every raw byte the app has emitted (accumulated in pump). Lets tests assert
    /// on control sequences the emulator consumes and never renders (e.g. OSC 52
    /// clipboard writes). Capture is bounded explicitly so a runaway child cannot
    /// consume unbounded test-runner memory.
    raw: *RawCapture,

    pub fn init(gpa: std.mem.Allocator, exe: [*:0]const u8, rows: u16, cols: u16) !Harness {
        return initArgs(gpa, exe, rows, cols, null);
    }

    /// Like init, but passes one extra CLI arg to the app (e.g. "--tty").
    pub fn initArgs(gpa: std.mem.Allocator, exe: [*:0]const u8, rows: u16, cols: u16, arg: ?[*:0]const u8) !Harness {
        var argv: [2]?[*:0]const u8 = .{ null, null };
        if (arg) |a| argv[0] = a;
        return initArgv(gpa, exe, rows, cols, argv[0..(if (arg != null) @as(usize, 1) else 0)]);
    }

    /// Like init, but passes extra CLI args (e.g. "-l", "dump.zon").
    pub fn initArgv(gpa: std.mem.Allocator, exe: [*:0]const u8, rows: u16, cols: u16, args: []const ?[*:0]const u8) !Harness {
        const argv = try gpa.allocSentinel(?[*:0]const u8, args.len + 1, null);
        defer gpa.free(argv);
        argv[0] = exe;
        for (args, 0..) |a, i| argv[i + 1] = a;

        var master: c_int = undefined;
        const ws = posix.winsize{ .row = rows, .col = cols, .xpixel = 0, .ypixel = 0 };
        const pid = forkpty(&master, null, null, &ws);
        if (pid == 0) {
            for ([_][*:0]const u8{ "PARDES_9P", "PARDES_PANE", "PARDES_FORWARD_LOOK" }) |name|
                if (unsetenv(name) != 0) _exit(126);
            _ = execvp(exe, argv.ptr);
            _exit(127);
        }
        const term = try gpa.create(ghostty_vt.Terminal);
        errdefer gpa.destroy(term);
        term.* = try ghostty_vt.Terminal.init(std.Io.Threaded.global_single_threaded.io(), gpa, .{
            .cols = cols,
            .rows = rows,
            .max_scrollback = 1024 * 1024,
        });
        errdefer term.deinit(gpa);
        // vtStream() captures a pointer to `term`; term is heap-allocated so the
        // pointer stays valid for the life of the harness.
        const stream = term.vtStream();
        const raw = try gpa.create(RawCapture);
        errdefer gpa.destroy(raw);
        raw.* = .{};
        return .{
            .gpa = gpa,
            .master = master,
            .pid = pid,
            .term = term,
            .stream = stream,
            .rows = rows,
            .cols = cols,
            .raw = raw,
        };
    }

    pub fn deinit(self: *Harness) void {
        posix.kill(self.pid, posix.SIG.KILL) catch {};
        _ = libc.close(self.master);
        self.stream.deinit();
        self.gpa.destroy(self.raw);
        self.term.deinit(self.gpa);
        self.gpa.destroy(self.term);
    }

    /// Write raw bytes to the pty (input to the app: keystrokes, mouse events).
    pub fn send(self: *Harness, bytes: []const u8) !void {
        var off: usize = 0;
        while (off < bytes.len) {
            const n = libc.write(self.master, bytes[off..].ptr, bytes.len - off);
            if (n < 0) {
                if (libc.errno(n) == .INTR) continue;
                return error.WriteFailed;
            }
            off += @intCast(n);
        }
    }

    /// Read pty output and feed it to our ghostty terminal for `ms` ms. After
    /// this, the grid reflects everything the app rendered so far.
    pub fn pump(self: *Harness, ms: i64) !void {
        const deadline = nowMs() + ms;
        var buf: [4096]u8 = undefined;
        while (nowMs() < deadline) {
            var fds = [_]posix.pollfd{.{ .fd = self.master, .events = posix.POLL.IN, .revents = 0 }};
            _ = posix.poll(&fds, 50) catch {};
            if ((fds[0].revents & posix.POLL.IN) != 0) {
                const n = posix.read(self.master, &buf) catch break;
                if (n == 0) break;
                self.recordRaw(buf[0..n]);
                self.stream.nextSlice(buf[0..n]);
            }
        }
        if (self.trace) self.traceScreen("pump");
    }

    /// Wait up to `ms` for the app to say something, feed whatever arrived to
    /// the emulator, and report whether anything did. `ms` = 0 polls. This is
    /// the event-driven half of `pump`: a caller that only cares about the
    /// SETTLED grid sleeps in poll until the app actually writes, instead of
    /// burning a fixed window per check (see snapshot.zig's waitStable).
    pub fn pumpOnce(self: *Harness, ms: i64) !bool {
        var fds = [_]posix.pollfd{.{ .fd = self.master, .events = posix.POLL.IN, .revents = 0 }};
        const ready = posix.poll(&fds, @intCast(@max(0, ms))) catch 0;
        if (ready == 0 or (fds[0].revents & posix.POLL.IN) == 0) return false;
        var buf: [4096]u8 = undefined;
        const n = posix.read(self.master, &buf) catch return false;
        if (n == 0) return false;
        self.recordRaw(buf[0..n]);
        self.stream.nextSlice(buf[0..n]);
        return true;
    }

    /// Bytes sitting in the pty that nobody has picked up — keystrokes the app
    /// has not read yet, or output we have not read yet (the master counts both
    /// directions). Zero is the proof that the app has actually CONSUMED the
    /// input just sent: without it, an app still asleep in its event loop looks
    /// exactly like an app that has finished. See snapshot.zig's waitStable.
    pub fn pending(self: *Harness) usize {
        // Darwin files FIONREAD under the socket ioctls rather than the
        // termios group std.posix.T exposes, and encodes it differently
        // besides — _IOR('f', 127, int) against linux's flat constant.
        // Neither is derivable from the other, so both are named.
        const FIONREAD: c_int = switch (@import("builtin").os.tag) {
            .linux => posix.T.FIONREAD,
            else => 0x4004667f,
        };
        var n: c_int = 0;
        if (posix.system.ioctl(self.master, FIONREAD, @intFromPtr(&n)) != 0) return 0;
        return if (n > 0) @intCast(n) else 0;
    }

    /// Resize both the pty (SIGWINCH to the app) and our terminal (grid reflows
    /// to the new size). Harness terminal first so it's ready for the app's
    /// re-render at the new size.
    pub fn resize(self: *Harness, rows: u16, cols: u16) !void {
        self.rows = rows;
        self.cols = cols;
        self.term.resize(self.gpa, .{ .cols = cols, .rows = rows }) catch {};
        const ws = posix.winsize{ .row = rows, .col = cols, .xpixel = 0, .ypixel = 0 };
        _ = posix.system.ioctl(self.master, TIOCSWINSZ, @intFromPtr(&ws));
    }

    /// The full viewport text (plainString), newline-joined rows. Caller frees.
    pub fn screenText(self: *Harness) ![]const u8 {
        return self.term.plainString(self.gpa);
    }

    /// Is `needle` present anywhere on the current screen?
    pub fn contains(self: *Harness, needle: []const u8) bool {
        const text = self.screenText() catch return false;
        defer self.gpa.free(text);
        return std.mem.indexOf(u8, text, needle) != null;
    }

    /// Wait up to `ms` for `needle` to appear on screen, pumping bytes the
    /// whole time. Replaces pollFor + setWinsize-repaint: the grid is checked
    /// directly each iteration.
    pub fn waitFor(self: *Harness, needle: []const u8, ms: i64) !bool {
        {
            const text = try self.screenText();
            defer self.gpa.free(text);
            if (std.mem.indexOf(u8, text, needle) != null) {
                if (self.trace) self.traceScreen("waitFor hit");
                return true;
            }
        }
        const deadline = nowMs() + ms;
        var buf: [4096]u8 = undefined;
        while (nowMs() < deadline) {
            var fds = [_]posix.pollfd{.{ .fd = self.master, .events = posix.POLL.IN, .revents = 0 }};
            _ = posix.poll(&fds, 50) catch {};
            if ((fds[0].revents & posix.POLL.IN) != 0) {
                const n = posix.read(self.master, &buf) catch break;
                if (n == 0) break;
                self.recordRaw(buf[0..n]);
                self.stream.nextSlice(buf[0..n]);
            }
            const text = try self.screenText();
            defer self.gpa.free(text);
            if (std.mem.indexOf(u8, text, needle) != null) {
                if (self.trace) self.traceScreen("waitFor hit");
                return true;
            }
        }
        if (self.trace) self.traceScreen("waitFor miss");
        return false;
    }

    /// Wait up to `ms` for `needle` to appear in the app's RAW output, pumping
    /// bytes the whole time. Same shape as `waitFor`, against `raw` rather than
    /// the grid: for control sequences the emulator swallows and never renders.
    pub fn waitForRaw(self: *Harness, needle: []const u8, ms: i64) bool {
        if (std.mem.indexOf(u8, self.raw.items, needle) != null) return true;
        const deadline = nowMs() + ms;
        var buf: [4096]u8 = undefined;
        while (nowMs() < deadline) {
            var fds = [_]posix.pollfd{.{ .fd = self.master, .events = posix.POLL.IN, .revents = 0 }};
            _ = posix.poll(&fds, 50) catch {};
            if ((fds[0].revents & posix.POLL.IN) == 0) continue;
            const n = posix.read(self.master, &buf) catch break;
            if (n == 0) break;
            self.recordRaw(buf[0..n]);
            self.stream.nextSlice(buf[0..n]);
            if (std.mem.indexOf(u8, self.raw.items, needle) != null) return true;
        }
        return false;
    }
    fn recordRaw(self: *Harness, bytes: []const u8) void {
        self.raw.appendSlice(bytes) catch |err| switch (err) {
            error.CaptureFull => {},
        };
    }

    /// The visual cursor position (viewport coords): { x, y }.
    pub fn cursor(self: *Harness) struct { x: u16, y: u16 } {
        return .{
            .x = self.term.screens.active.cursor.x,
            .y = self.term.screens.active.cursor.y,
        };
    }

    /// True if the shell is at a prompt (OSC 133 semantic prompt). Requires
    /// shell integration; false if the shell is outputting or has no integration.
    pub fn atPrompt(self: *Harness) bool {
        return self.term.cursorIsAtPrompt();
    }

    /// Print the screen grid (clean text, not raw bytes) for debugging on
    /// failure. Also shows the cursor position and screen size.
    pub fn dump(self: *Harness, msg: []const u8) void {
        const text = self.screenText() catch {
            std.debug.print("E2E FAIL: {s}\n(could not read screen)\n", .{msg});
            return;
        };
        defer self.gpa.free(text);
        const c = self.cursor();
        std.debug.print("E2E FAIL: {s}\nscreen {d}x{d} cursor=({d},{d}):\n{s}\n", .{
            msg, self.cols, self.rows, c.x, c.y, text,
        });
    }

    /// trace-mode screen snapshot: print the current grid + cursor + size to
    /// stderr (always, not just on failure). Bounded by a header so the live
    /// stream of snapshots is easy to scan.
    pub fn traceScreen(self: *Harness, tag: []const u8) void {
        const text = self.screenText() catch return;
        defer self.gpa.free(text);
        const c = self.cursor();
        std.debug.print("\n[trace {s}] screen {d}x{d} cursor=({d},{d}):\n{s}\n[/trace]\n", .{
            tag, self.cols, self.rows, c.x, c.y, text,
        });
    }

    // ---- assertions (dump on failure, return error.ExpectFailed) ----

    pub fn expectWaitFor(self: *Harness, needle: []const u8, ms: i64, msg: []const u8) !void {
        if (!try self.waitFor(needle, ms)) {
            self.dump(msg);
            return error.ExpectFailed;
        }
    }

    pub fn expectContains(self: *Harness, needle: []const u8, msg: []const u8) !void {
        if (!self.contains(needle)) {
            self.dump(msg);
            return error.ExpectFailed;
        }
    }

    pub fn expectNotContains(self: *Harness, needle: []const u8, msg: []const u8) !void {
        if (self.contains(needle)) {
            self.dump(msg);
            return error.ExpectFailed;
        }
    }

    /// Assert a byte sequence appears anywhere in the app's raw output so far.
    /// For control sequences the emulator swallows and never renders (OSC 52 etc.).
    pub fn expectRawContains(self: *Harness, needle: []const u8, msg: []const u8) !void {
        if (std.mem.indexOf(u8, self.raw.items, needle) == null) {
            std.debug.print("E2E FAIL: {s}\n(raw output has no {any})\n", .{ msg, needle });
            return error.ExpectFailed;
        }
    }

    /// Assert a byte sequence appears in the app's raw output, waiting for it.
    /// A fixed `pump` before `expectRawContains` budgets a STARTUP instead of
    /// waiting for an answer, and a cold 70 MB Debug binary on a loaded machine
    /// overruns any such budget.
    pub fn expectRawWaitFor(self: *Harness, needle: []const u8, ms: i64, msg: []const u8) !void {
        if (!self.waitForRaw(needle, ms)) {
            std.debug.print("E2E FAIL: {s}\n(raw output has no {any})\n", .{ msg, needle });
            return error.ExpectFailed;
        }
    }
};

/// Write a file (helper for test setup, raw libc).
pub fn writeFile(path: [*:0]const u8, data: []const u8) !void {
    const fd = libc.open(path, .{ .ACCMODE = .WRONLY, .CREAT = true, .TRUNC = true }, @as(libc.mode_t, 0o644));
    if (fd < 0) return error.OpenFailed;
    defer _ = libc.close(fd);
    var off: usize = 0;
    while (off < data.len) {
        const w = libc.write(fd, data[off..].ptr, data.len - off);
        if (w <= 0) break;
        off += @intCast(w);
    }
}