//! Widget Testing Framework for zcatui
//!
//! Provides utilities for testing widgets in isolation:
//! - TestBackend: Mock backend for capturing output
//! - TestTerminal: Terminal that captures frames
//! - Assertions: Test helpers for widget behavior
//! - Snapshots: Golden file testing
//!
//! Example:
//! ```zig
//! const testing = @import("testing.zig");
//! const widgets = @import("root.zig").widgets;
//!
//! test "paragraph renders correctly" {
//!     var harness = testing.WidgetHarness.init(testing.testing_allocator, 40, 10);
//!     defer harness.deinit();
//!
//!     const para = widgets.Paragraph.init("Hello, World!");
//!     harness.render(para);
//!
//!     try harness.expectText(0, 0, "Hello, World!");
//!     try harness.expectStyle(0, 0, .{ .foreground = .white });
//! }
//! ```

const std = @import("std");
const Buffer = @import("buffer.zig").Buffer;
const Cell = @import("buffer.zig").Cell;
const Rect = @import("buffer.zig").Rect;
const Style = @import("style.zig").Style;
const Color = @import("style.zig").Color;

/// Test allocator for use in tests
pub const testing_allocator = std.testing.allocator;

// ============================================================================
// Test Backend
// ============================================================================

/// A mock backend that captures all output for testing
pub const TestBackend = struct {
    /// Captured ANSI sequences
    output: std.ArrayListUnmanaged(u8),
    allocator: std.mem.Allocator,
    /// Cursor position
    cursor_x: u16 = 0,
    cursor_y: u16 = 0,
    /// Cursor visible
    cursor_visible: bool = true,
    /// Terminal size
    width: u16,
    height: u16,
    /// Alternate screen active
    alternate_screen: bool = false,
    /// Raw mode active
    raw_mode: bool = false,
    /// Mouse capture active
    mouse_capture: bool = false,

    pub fn init(allocator: std.mem.Allocator, width: u16, height: u16) TestBackend {
        return .{
            .output = .{},
            .allocator = allocator,
            .width = width,
            .height = height,
        };
    }

    pub fn deinit(self: *TestBackend) void {
        self.output.deinit(self.allocator);
    }

    /// Write output (captured)
    pub fn write(self: *TestBackend, data: []const u8) !void {
        try self.output.appendSlice(self.allocator, data);
    }

    /// Clear captured output
    pub fn clearOutput(self: *TestBackend) void {
        self.output.clearRetainingCapacity();
    }

    /// Get captured output as string
    pub fn getOutput(self: *const TestBackend) []const u8 {
        return self.output.items;
    }

    /// Check if output contains a string
    pub fn outputContains(self: *const TestBackend, needle: []const u8) bool {
        return std.mem.indexOf(u8, self.output.items, needle) != null;
    }

    /// Simulate terminal resize
    pub fn resize(self: *TestBackend, width: u16, height: u16) void {
        self.width = width;
        self.height = height;
    }

    /// Get terminal size
    pub fn size(self: *const TestBackend) struct { width: u16, height: u16 } {
        return .{ .width = self.width, .height = self.height };
    }
};

// ============================================================================
// Widget Test Harness
// ============================================================================

/// Test harness for widget testing
pub const WidgetHarness = struct {
    allocator: std.mem.Allocator,
    buffer: Buffer,
    area: Rect,
    /// Previous buffer for diff testing
    prev_buffer: ?Buffer = null,
    /// Frame counter
    frame_count: u32 = 0,

    /// Initialize test harness with given dimensions
    pub fn init(allocator: std.mem.Allocator, width: u16, height: u16) WidgetHarness {
        const area = Rect.init(0, 0, width, height);
        return .{
            .allocator = allocator,
            .buffer = Buffer.init(allocator, area) catch unreachable,
            .area = area,
        };
    }

    /// Deinitialize
    pub fn deinit(self: *WidgetHarness) void {
        self.buffer.deinit();
        if (self.prev_buffer) |*prev| {
            prev.deinit();
        }
    }

    /// Reset buffer for new test
    pub fn reset(self: *WidgetHarness) void {
        self.buffer.clear();
        self.frame_count = 0;
    }

    /// Render a widget to the test buffer
    pub fn render(self: *WidgetHarness, widget: anytype) void {
        widget.render(self.area, &self.buffer);
        self.frame_count += 1;
    }

    /// Render a widget with state
    pub fn renderWithState(self: *WidgetHarness, widget: anytype, state: anytype) void {
        widget.render(self.area, &self.buffer, state);
        self.frame_count += 1;
    }

    /// Render to a specific area within the harness
    pub fn renderTo(self: *WidgetHarness, widget: anytype, area: Rect) void {
        widget.render(area, &self.buffer);
        self.frame_count += 1;
    }

    // ========================================================================
    // Assertions
    // ========================================================================

    /// Get cell at position
    pub fn getCell(self: *const WidgetHarness, x: u16, y: u16) ?*const Cell {
        return self.buffer.get(x, y);
    }

    /// Get text at position (single character)
    pub fn getChar(self: *const WidgetHarness, x: u16, y: u16) ?[]const u8 {
        if (self.buffer.get(x, y)) |cell| {
            return cell.symbol.slice();
        }
        return null;
    }

    /// Get text from a row
    pub fn getRowText(self: *const WidgetHarness, y: u16) []const u8 {
        var result: [256]u8 = undefined;
        var len: usize = 0;

        var x: u16 = 0;
        while (x < self.area.width) : (x += 1) {
            if (self.buffer.get(x, y)) |cell| {
                const sym = cell.symbol.slice();
                if (len + sym.len <= result.len) {
                    @memcpy(result[len..][0..sym.len], sym);
                    len += sym.len;
                }
            }
        }

        // Trim trailing spaces
        while (len > 0 and result[len - 1] == ' ') {
            len -= 1;
        }

        return result[0..len];
    }

    /// Expect text at position
    pub fn expectText(self: *const WidgetHarness, x: u16, y: u16, expected: []const u8) !void {
        var pos_x = x;
        for (expected) |char| {
            if (self.buffer.get(pos_x, y)) |cell| {
                const sym = cell.symbol.slice();
                if (sym.len > 0) {
                    try std.testing.expectEqual(char, sym[0]);
                }
            }
            pos_x += 1;
        }
    }

    /// Expect style at position
    pub fn expectStyle(self: *const WidgetHarness, x: u16, y: u16, expected_style: Style) !void {
        if (self.buffer.get(x, y)) |cell| {
            try std.testing.expectEqual(expected_style.foreground, cell.style.foreground);
            try std.testing.expectEqual(expected_style.background, cell.style.background);
        } else {
            return error.CellNotFound;
        }
    }

    /// Expect foreground color at position
    pub fn expectFg(self: *const WidgetHarness, x: u16, y: u16, expected: Color) !void {
        if (self.buffer.get(x, y)) |cell| {
            try std.testing.expectEqual(expected, cell.style.foreground);
        } else {
            return error.CellNotFound;
        }
    }

    /// Expect background color at position
    pub fn expectBg(self: *const WidgetHarness, x: u16, y: u16, expected: Color) !void {
        if (self.buffer.get(x, y)) |cell| {
            try std.testing.expectEqual(expected, cell.style.background);
        } else {
            return error.CellNotFound;
        }
    }

    /// Expect area to be empty (all spaces)
    pub fn expectEmpty(self: *const WidgetHarness, area: Rect) !void {
        var y = area.y;
        while (y < area.bottom()) : (y += 1) {
            var x = area.x;
            while (x < area.right()) : (x += 1) {
                if (self.buffer.get(x, y)) |cell| {
                    const sym = cell.symbol.slice();
                    if (sym.len > 0 and sym[0] != ' ') {
                        std.debug.print("Expected empty at ({}, {}), found: '{s}'\n", .{ x, y, sym });
                        return error.NotEmpty;
                    }
                }
            }
        }
    }

    /// Expect area to not be empty
    pub fn expectNotEmpty(self: *const WidgetHarness, area: Rect) !void {
        var y = area.y;
        while (y < area.bottom()) : (y += 1) {
            var x = area.x;
            while (x < area.right()) : (x += 1) {
                if (self.buffer.get(x, y)) |cell| {
                    const sym = cell.symbol.slice();
                    if (sym.len > 0 and sym[0] != ' ') {
                        return; // Found non-empty
                    }
                }
            }
        }
        return error.IsEmpty;
    }

    /// Check if a character exists anywhere in the buffer
    pub fn containsChar(self: *const WidgetHarness, char: u8) bool {
        var y: u16 = 0;
        while (y < self.area.height) : (y += 1) {
            var x: u16 = 0;
            while (x < self.area.width) : (x += 1) {
                if (self.buffer.get(x, y)) |cell| {
                    const sym = cell.symbol.slice();
                    if (sym.len > 0 and sym[0] == char) {
                        return true;
                    }
                }
            }
        }
        return false;
    }

    /// Check if text exists anywhere in the buffer
    pub fn containsText(self: *const WidgetHarness, text: []const u8) bool {
        var y: u16 = 0;
        while (y < self.area.height) : (y += 1) {
            var x: u16 = 0;
            while (x < self.area.width -| @as(u16, @intCast(text.len))) : (x += 1) {
                var matches = true;
                for (text, 0..) |char, i| {
                    if (self.buffer.get(x + @as(u16, @intCast(i)), y)) |cell| {
                        const sym = cell.symbol.slice();
                        if (sym.len == 0 or sym[0] != char) {
                            matches = false;
                            break;
                        }
                    } else {
                        matches = false;
                        break;
                    }
                }
                if (matches) return true;
            }
        }
        return false;
    }

    // ========================================================================
    // Snapshot Testing
    // ========================================================================

    /// Render buffer to string for snapshot comparison
    pub fn toString(self: *const WidgetHarness) []const u8 {
        var result: [4096]u8 = undefined;
        var len: usize = 0;

        var y: u16 = 0;
        while (y < self.area.height) : (y += 1) {
            var x: u16 = 0;
            while (x < self.area.width) : (x += 1) {
                if (self.buffer.get(x, y)) |cell| {
                    const sym = cell.symbol.slice();
                    if (sym.len > 0 and len + sym.len <= result.len) {
                        @memcpy(result[len..][0..sym.len], sym);
                        len += sym.len;
                    } else if (len < result.len) {
                        result[len] = ' ';
                        len += 1;
                    }
                } else if (len < result.len) {
                    result[len] = ' ';
                    len += 1;
                }
            }
            if (len < result.len) {
                result[len] = '\n';
                len += 1;
            }
        }

        return result[0..len];
    }

    /// Print buffer for debugging
    pub fn debugPrint(self: *const WidgetHarness) void {
        std.debug.print("\n=== Buffer ({} x {}) ===\n", .{ self.area.width, self.area.height });

        var y: u16 = 0;
        while (y < self.area.height) : (y += 1) {
            var x: u16 = 0;
            while (x < self.area.width) : (x += 1) {
                if (self.buffer.get(x, y)) |cell| {
                    const sym = cell.symbol.slice();
                    if (sym.len > 0) {
                        std.debug.print("{s}", .{sym});
                    } else {
                        std.debug.print(" ", .{});
                    }
                } else {
                    std.debug.print(" ", .{});
                }
            }
            std.debug.print("|\n", .{});
        }
        std.debug.print("======================\n", .{});
    }
};

// ============================================================================
// Event Simulation
// ============================================================================

const Event = @import("event.zig").Event;
const KeyEvent = @import("event.zig").KeyEvent;
const KeyCode = @import("event.zig").KeyCode;
const MouseEvent = @import("event.zig").MouseEvent;
const MouseButton = @import("event.zig").MouseButton;
const MouseEventKind = @import("event.zig").MouseEventKind;

/// Helper to create key events for testing
pub const SimulatedInput = struct {
    /// Create a key press event
    pub fn key(code: KeyCode) Event {
        return .{
            .key = .{
                .code = code,
                .modifiers = .{},
                .kind = .press,
            },
        };
    }

    /// Create a key press with char
    pub fn char(c: u21) Event {
        return .{
            .key = .{
                .code = .{ .char = c },
                .modifiers = .{},
                .kind = .press,
            },
        };
    }

    /// Create a key with modifiers
    pub fn keyWithMod(code: KeyCode, ctrl: bool, alt: bool, shift: bool) Event {
        return .{
            .key = .{
                .code = code,
                .modifiers = .{
                    .ctrl = ctrl,
                    .alt = alt,
                    .shift = shift,
                },
                .kind = .press,
            },
        };
    }

    /// Create mouse click event
    pub fn click(col: u16, row: u16, button: MouseButton) Event {
        return .{
            .mouse = .{
                .column = col,
                .row = row,
                .kind = .down,
                .button = button,
                .modifiers = .{},
            },
        };
    }

    /// Create mouse scroll event
    pub fn scroll(col: u16, row: u16, down: bool) Event {
        return .{
            .mouse = .{
                .column = col,
                .row = row,
                .kind = if (down) .scroll_down else .scroll_up,
                .button = .none,
                .modifiers = .{},
            },
        };
    }

    /// Create resize event
    pub fn resize(width: u16, height: u16) Event {
        return .{
            .resize = .{
                .width = width,
                .height = height,
            },
        };
    }
};

// ============================================================================
// Benchmark Utilities
// ============================================================================

/// Simple timing utility for widget benchmarks
pub const Benchmark = struct {
    start_time: i128,
    iterations: u32 = 0,
    total_ns: i128 = 0,

    pub fn start() Benchmark {
        return .{
            .start_time = std.time.nanoTimestamp(),
        };
    }

    pub fn lap(self: *Benchmark) void {
        const now = std.time.nanoTimestamp();
        self.total_ns += now - self.start_time;
        self.iterations += 1;
        self.start_time = now;
    }

    pub fn avgNs(self: *const Benchmark) i128 {
        if (self.iterations == 0) return 0;
        return @divTrunc(self.total_ns, self.iterations);
    }

    pub fn avgUs(self: *const Benchmark) f64 {
        return @as(f64, @floatFromInt(self.avgNs())) / 1000.0;
    }

    pub fn avgMs(self: *const Benchmark) f64 {
        return @as(f64, @floatFromInt(self.avgNs())) / 1_000_000.0;
    }

    pub fn report(self: *const Benchmark, name: []const u8) void {
        std.debug.print(
            "{s}: {} iterations, avg {d:.2}µs ({d:.2}ms total)\n",
            .{
                name,
                self.iterations,
                self.avgUs(),
                @as(f64, @floatFromInt(self.total_ns)) / 1_000_000.0,
            },
        );
    }
};

// ============================================================================
// Tests
// ============================================================================

test "TestBackend captures output" {
    var backend = TestBackend.init(testing_allocator, 80, 24);
    defer backend.deinit();

    try backend.write("Hello");
    try backend.write(" World");

    try std.testing.expectEqualStrings("Hello World", backend.getOutput());
    try std.testing.expect(backend.outputContains("World"));
    try std.testing.expect(!backend.outputContains("Foo"));
}

test "WidgetHarness basic operations" {
    var harness = WidgetHarness.init(testing_allocator, 20, 5);
    defer harness.deinit();

    // Test basic harness creation
    try std.testing.expectEqual(@as(u16, 20), harness.area.width);
    try std.testing.expectEqual(@as(u16, 5), harness.area.height);
}

test "SimulatedInput creates events" {
    const key_event = SimulatedInput.key(.enter);
    try std.testing.expectEqual(KeyCode.enter, key_event.key.code);

    const char_event = SimulatedInput.char('a');
    try std.testing.expectEqual(KeyCode{ .char = 'a' }, char_event.key.code);

    const click_event = SimulatedInput.click(10, 5, .left);
    try std.testing.expectEqual(@as(u16, 10), click_event.mouse.column);
    try std.testing.expectEqual(@as(u16, 5), click_event.mouse.row);
}

test "Benchmark timing" {
    var bench = Benchmark.start();

    var i: u32 = 0;
    while (i < 100) : (i += 1) {
        // Simulate some work
        _ = @as(u32, 0) +% @as(u32, 1);
        bench.lap();
    }

    try std.testing.expectEqual(@as(u32, 100), bench.iterations);
    try std.testing.expect(bench.total_ns > 0);
}