presentar_terminal/

app.rs

//! TUI application runner with Jidoka verification gates.
//!
//! ## Non-Blocking UI Pattern (CB-INPUT-006)
//!
//! For applications with heavy data collection (system monitors, dashboards),
//! use the [`AsyncCollector`] pattern to ensure the main thread never blocks.
//!
//! ```ignore
//! // Background thread owns collectors, sends snapshots through channel
//! let (tx, rx) = mpsc::channel::<MySnapshot>();
//!
//! std::thread::spawn(move || {
//!     let mut collector = MyCollector::new();
//!     loop {
//!         let snapshot = collector.collect();  // Can take seconds
//!         tx.send(snapshot).ok();
//!         std::thread::sleep(Duration::from_secs(1));
//!     }
//! });
//!
//! // Main thread: input + render only (always <16ms)
//! loop {
//!     while let Ok(snapshot) = rx.try_recv() {
//!         app.apply_snapshot(snapshot);  // O(1) operation
//!     }
//!     app.handle_input();  // Non-blocking
//!     app.render();        // <16ms budget
//! }
//! ```

#![allow(dead_code, unreachable_pub)]

use crate::color::ColorMode;
use crate::direct::{CellBuffer, DiffRenderer, DirectTerminalCanvas};
use crate::error::{TuiError, VerificationError};
use crate::input::InputHandler;
use crossterm::{
    cursor,
    event::{self, Event as CrosstermEvent, KeyCode},
    execute,
    terminal::{disable_raw_mode, enable_raw_mode, EnterAlternateScreen, LeaveAlternateScreen},
};
use presentar_core::{Constraints, Rect, Widget};
use std::io::{self, Stdout, Write};
use std::time::{Duration, Instant};

// =============================================================================
// Non-Blocking UI Pattern (CB-INPUT-006)
// =============================================================================

/// Snapshot of collected metrics, transportable via channel.
///
/// Implement this trait for data structures that are sent from a background
/// collector thread to the main UI thread.
///
/// # Requirements
/// - Must be `Clone` (for potential buffering)
/// - Must be `Send` (for channel transport)
/// - Must be `'static` (for thread safety)
pub trait Snapshot: Clone + Send + 'static {
    /// Create an empty snapshot for initial state before first collection.
    fn empty() -> Self;
}

/// Background collector that produces snapshots.
///
/// Implement this trait for objects that collect metrics in a background thread.
/// The collector owns all heavy I/O objects (System, Disks, Networks, etc.)
/// and produces lightweight snapshots that can be sent through a channel.
///
/// # Example
/// ```ignore
/// struct SystemCollector {
///     system: System,
///     disks: Disks,
/// }
///
/// impl AsyncCollector for SystemCollector {
///     type Snapshot = MetricsSnapshot;
///
///     fn collect(&mut self) -> MetricsSnapshot {
///         self.system.refresh_all();  // Heavy I/O
///         MetricsSnapshot {
///             cpu_usage: self.system.global_cpu_usage(),
///             // ... extract other data
///         }
///     }
/// }
/// ```
pub trait AsyncCollector: Send + 'static {
    /// The snapshot type produced by this collector.
    type Snapshot: Snapshot;

    /// Collect metrics and return a snapshot.
    ///
    /// This method may take seconds to complete (heavy I/O).
    /// It runs in a background thread, never blocking the UI.
    fn collect(&mut self) -> Self::Snapshot;
}

/// Application that can apply snapshots to update its state.
///
/// Implement this trait for your application state. The `apply_snapshot`
/// method is called on the main thread and MUST complete in <1ms.
///
/// # Example
/// ```ignore
/// impl SnapshotReceiver for MyApp {
///     type Snapshot = MetricsSnapshot;
///
///     fn apply_snapshot(&mut self, snapshot: MetricsSnapshot) {
///         // O(1) operations only - just copy/swap data
///         self.cpu_usage = snapshot.cpu_usage;
///         self.processes = snapshot.processes;
///     }
/// }
/// ```
pub trait SnapshotReceiver {
    /// The snapshot type this receiver accepts.
    type Snapshot: Snapshot;

    /// Apply a snapshot to update the application state.
    ///
    /// **MUST be O(1) and complete in <1ms.**
    /// Only perform simple assignments, no I/O or heavy computation.
    fn apply_snapshot(&mut self, snapshot: Self::Snapshot);
}

/// QA timing diagnostics for non-blocking UI verification.
///
/// Use this struct to collect timing data for `--qa-timing` output.
#[derive(Debug, Clone, Default)]
pub struct QaTimings {
    /// Input event processing times in microseconds.
    pub input_times_us: Vec<u64>,
    /// Lock acquisition times in microseconds (should be 0 with channel pattern).
    pub lock_times_us: Vec<u64>,
    /// Render times in microseconds.
    pub render_times_us: Vec<u64>,
    /// Last collect duration in microseconds (from background thread).
    pub last_collect_us: u64,
}

impl QaTimings {
    /// Create new QA timing collector.
    #[must_use]
    pub fn new() -> Self {
        Self::default()
    }

    /// Record an input event processing time.
    pub fn record_input(&mut self, duration: Duration) {
        self.input_times_us.push(duration.as_micros() as u64);
    }

    /// Record a lock acquisition time.
    pub fn record_lock(&mut self, duration: Duration) {
        self.lock_times_us.push(duration.as_micros() as u64);
    }

    /// Record a render time.
    pub fn record_render(&mut self, duration: Duration) {
        self.render_times_us.push(duration.as_micros() as u64);
    }

    /// Format timing report for stderr output.
    #[must_use]
    pub fn format_report(&self) -> String {
        let avg = |v: &[u64]| {
            if v.is_empty() {
                0
            } else {
                v.iter().sum::<u64>() / v.len() as u64
            }
        };
        let max = |v: &[u64]| v.iter().max().copied().unwrap_or(0);

        format!(
            "[QA] input: avg={}us max={}us | lock: avg={}us max={}us | render: avg={}us max={}us | collect: {}us",
            avg(&self.input_times_us), max(&self.input_times_us),
            avg(&self.lock_times_us), max(&self.lock_times_us),
            avg(&self.render_times_us), max(&self.render_times_us),
            self.last_collect_us
        )
    }

    /// Clear accumulated timing data.
    pub fn clear(&mut self) {
        self.input_times_us.clear();
        self.lock_times_us.clear();
        self.render_times_us.clear();
    }
}

// =============================================================================
// Terminal Abstraction
// =============================================================================

/// Terminal abstraction for testability.
pub trait Terminal {
    /// Enter raw mode and alternate screen.
    fn enter(&mut self) -> Result<(), TuiError>;
    /// Leave alternate screen and raw mode.
    fn leave(&mut self) -> Result<(), TuiError>;
    /// Get terminal size (width, height).
    fn size(&self) -> Result<(u16, u16), TuiError>;
    /// Poll for events with timeout.
    fn poll(&self, timeout: Duration) -> Result<bool, TuiError>;
    /// Read the next event.
    fn read_event(&self) -> Result<CrosstermEvent, TuiError>;
    /// Flush output.
    fn flush(
        &mut self,
        buffer: &mut CellBuffer,
        renderer: &mut DiffRenderer,
    ) -> Result<(), TuiError>;
    /// Enable mouse capture.
    fn enable_mouse(&mut self) -> Result<(), TuiError>;
    /// Disable mouse capture.
    fn disable_mouse(&mut self) -> Result<(), TuiError>;
}

/// Backend trait for raw terminal operations (crossterm calls).
/// This layer exists purely for testability.
pub trait TerminalBackend {
    fn enable_raw_mode(&mut self) -> Result<(), TuiError>;
    fn disable_raw_mode(&mut self) -> Result<(), TuiError>;
    fn enter_alternate_screen(&mut self) -> Result<(), TuiError>;
    fn leave_alternate_screen(&mut self) -> Result<(), TuiError>;
    fn hide_cursor(&mut self) -> Result<(), TuiError>;
    fn show_cursor(&mut self) -> Result<(), TuiError>;
    fn size(&self) -> Result<(u16, u16), TuiError>;
    fn poll(&self, timeout: Duration) -> Result<bool, TuiError>;
    fn read_event(&self) -> Result<CrosstermEvent, TuiError>;
    fn write_flush(
        &mut self,
        buffer: &mut CellBuffer,
        renderer: &mut DiffRenderer,
    ) -> Result<(), TuiError>;
    fn enable_mouse_capture(&mut self) -> Result<(), TuiError>;
    fn disable_mouse_capture(&mut self) -> Result<(), TuiError>;
}

/// Real crossterm backend.
pub struct CrosstermBackend {
    stdout: Stdout,
}

impl CrosstermBackend {
    pub fn new() -> Self {
        Self {
            stdout: io::stdout(),
        }
    }
}

impl Default for CrosstermBackend {
    fn default() -> Self {
        Self::new()
    }
}

impl TerminalBackend for CrosstermBackend {
    fn enable_raw_mode(&mut self) -> Result<(), TuiError> {
        enable_raw_mode()?;
        Ok(())
    }
    fn disable_raw_mode(&mut self) -> Result<(), TuiError> {
        let _ = disable_raw_mode();
        Ok(())
    }
    fn enter_alternate_screen(&mut self) -> Result<(), TuiError> {
        execute!(self.stdout, EnterAlternateScreen)?;
        Ok(())
    }
    fn leave_alternate_screen(&mut self) -> Result<(), TuiError> {
        let _ = execute!(self.stdout, LeaveAlternateScreen);
        Ok(())
    }
    fn hide_cursor(&mut self) -> Result<(), TuiError> {
        execute!(self.stdout, cursor::Hide)?;
        Ok(())
    }
    fn show_cursor(&mut self) -> Result<(), TuiError> {
        let _ = execute!(self.stdout, cursor::Show);
        Ok(())
    }
    fn size(&self) -> Result<(u16, u16), TuiError> {
        Ok(crossterm::terminal::size()?)
    }
    fn poll(&self, timeout: Duration) -> Result<bool, TuiError> {
        Ok(event::poll(timeout)?)
    }
    fn read_event(&self) -> Result<CrosstermEvent, TuiError> {
        Ok(event::read()?)
    }
    fn write_flush(
        &mut self,
        buffer: &mut CellBuffer,
        renderer: &mut DiffRenderer,
    ) -> Result<(), TuiError> {
        renderer.flush(buffer, &mut self.stdout)?;
        self.stdout.flush()?;
        Ok(())
    }
    fn enable_mouse_capture(&mut self) -> Result<(), TuiError> {
        execute!(self.stdout, crossterm::event::EnableMouseCapture)?;
        Ok(())
    }
    fn disable_mouse_capture(&mut self) -> Result<(), TuiError> {
        let _ = execute!(self.stdout, crossterm::event::DisableMouseCapture);
        Ok(())
    }
}

/// Testable backend with generic writer for capturing escape sequences.
/// This backend allows testing terminal output without a real TTY.
#[allow(clippy::struct_excessive_bools)]
pub struct TestableBackend<W: Write> {
    writer: W,
    size: (u16, u16),
    raw_mode: bool,
    alternate_screen: bool,
    cursor_hidden: bool,
    mouse_captured: bool,
    events: std::cell::RefCell<std::collections::VecDeque<CrosstermEvent>>,
    poll_results: std::cell::RefCell<std::collections::VecDeque<bool>>,
}

impl<W: Write> TestableBackend<W> {
    /// Create a new testable backend with the given writer and size.
    pub fn new(writer: W, width: u16, height: u16) -> Self {
        Self {
            writer,
            size: (width, height),
            raw_mode: false,
            alternate_screen: false,
            cursor_hidden: false,
            mouse_captured: false,
            events: std::cell::RefCell::new(std::collections::VecDeque::new()),
            poll_results: std::cell::RefCell::new(std::collections::VecDeque::new()),
        }
    }

    /// Queue events to be returned by `read_event`.
    pub fn with_events(self, events: Vec<CrosstermEvent>) -> Self {
        *self.events.borrow_mut() = events.into_iter().collect();
        self
    }

    /// Queue poll results.
    pub fn with_polls(self, polls: Vec<bool>) -> Self {
        *self.poll_results.borrow_mut() = polls.into_iter().collect();
        self
    }

    /// Check if raw mode was enabled.
    pub fn is_raw_mode(&self) -> bool {
        self.raw_mode
    }

    /// Check if alternate screen was entered.
    pub fn is_alternate_screen(&self) -> bool {
        self.alternate_screen
    }

    /// Check if cursor is hidden.
    pub fn is_cursor_hidden(&self) -> bool {
        self.cursor_hidden
    }

    /// Check if mouse is captured.
    pub fn is_mouse_captured(&self) -> bool {
        self.mouse_captured
    }

    /// Get the underlying writer (consumes self).
    pub fn into_writer(self) -> W {
        self.writer
    }
}

impl<W: Write> TerminalBackend for TestableBackend<W> {
    fn enable_raw_mode(&mut self) -> Result<(), TuiError> {
        self.raw_mode = true;
        Ok(())
    }

    fn disable_raw_mode(&mut self) -> Result<(), TuiError> {
        self.raw_mode = false;
        Ok(())
    }

    fn enter_alternate_screen(&mut self) -> Result<(), TuiError> {
        self.alternate_screen = true;
        // Write the actual escape sequence for testing
        execute!(self.writer, EnterAlternateScreen)?;
        Ok(())
    }

    fn leave_alternate_screen(&mut self) -> Result<(), TuiError> {
        self.alternate_screen = false;
        let _ = execute!(self.writer, LeaveAlternateScreen);
        Ok(())
    }

    fn hide_cursor(&mut self) -> Result<(), TuiError> {
        self.cursor_hidden = true;
        execute!(self.writer, cursor::Hide)?;
        Ok(())
    }

    fn show_cursor(&mut self) -> Result<(), TuiError> {
        self.cursor_hidden = false;
        let _ = execute!(self.writer, cursor::Show);
        Ok(())
    }

    fn size(&self) -> Result<(u16, u16), TuiError> {
        Ok(self.size)
    }

    fn poll(&self, _timeout: Duration) -> Result<bool, TuiError> {
        Ok(self.poll_results.borrow_mut().pop_front().unwrap_or(false))
    }

    fn read_event(&self) -> Result<CrosstermEvent, TuiError> {
        self.events
            .borrow_mut()
            .pop_front()
            .ok_or_else(|| TuiError::Io(io::Error::new(io::ErrorKind::WouldBlock, "no events")))
    }

    fn write_flush(
        &mut self,
        buffer: &mut CellBuffer,
        renderer: &mut DiffRenderer,
    ) -> Result<(), TuiError> {
        renderer.flush(buffer, &mut self.writer)?;
        self.writer.flush()?;
        Ok(())
    }

    fn enable_mouse_capture(&mut self) -> Result<(), TuiError> {
        self.mouse_captured = true;
        execute!(self.writer, crossterm::event::EnableMouseCapture)?;
        Ok(())
    }

    fn disable_mouse_capture(&mut self) -> Result<(), TuiError> {
        self.mouse_captured = false;
        let _ = execute!(self.writer, crossterm::event::DisableMouseCapture);
        Ok(())
    }
}

/// Generic terminal implementation using a backend.
pub struct GenericTerminal<B: TerminalBackend> {
    backend: B,
}

impl<B: TerminalBackend> GenericTerminal<B> {
    pub fn new(backend: B) -> Self {
        Self { backend }
    }
}

impl<B: TerminalBackend> Terminal for GenericTerminal<B> {
    fn enter(&mut self) -> Result<(), TuiError> {
        self.backend.enable_raw_mode()?;
        self.backend.enter_alternate_screen()?;
        self.backend.hide_cursor()?;
        Ok(())
    }

    fn leave(&mut self) -> Result<(), TuiError> {
        self.backend.show_cursor()?;
        self.backend.leave_alternate_screen()?;
        self.backend.disable_raw_mode()?;
        Ok(())
    }

    fn size(&self) -> Result<(u16, u16), TuiError> {
        self.backend.size()
    }

    fn poll(&self, timeout: Duration) -> Result<bool, TuiError> {
        self.backend.poll(timeout)
    }

    fn read_event(&self) -> Result<CrosstermEvent, TuiError> {
        self.backend.read_event()
    }

    fn flush(
        &mut self,
        buffer: &mut CellBuffer,
        renderer: &mut DiffRenderer,
    ) -> Result<(), TuiError> {
        self.backend.write_flush(buffer, renderer)
    }

    fn enable_mouse(&mut self) -> Result<(), TuiError> {
        self.backend.enable_mouse_capture()
    }

    fn disable_mouse(&mut self) -> Result<(), TuiError> {
        self.backend.disable_mouse_capture()
    }
}

/// Convenience alias for crossterm-backed terminal.
pub type CrosstermTerminal = GenericTerminal<CrosstermBackend>;

/// Configuration for the TUI application.
#[derive(Debug, Clone)]
pub struct TuiConfig {
    /// Tick rate in milliseconds for input polling.
    pub tick_rate_ms: u64,
    /// Enable mouse support.
    pub enable_mouse: bool,
    /// Color mode (auto-detected if not specified).
    pub color_mode: Option<ColorMode>,
    /// Skip Brick verification (DANGEROUS - for debugging only).
    pub skip_verification: bool,
    /// Target frame rate (used for budget calculation).
    pub target_fps: u32,
}

impl Default for TuiConfig {
    fn default() -> Self {
        Self {
            tick_rate_ms: 250,
            enable_mouse: false,
            color_mode: None,
            target_fps: 60,
            skip_verification: false,
        }
    }
}

impl TuiConfig {
    /// Create a high-performance config (60fps, fast tick).
    #[must_use]
    pub fn high_performance() -> Self {
        Self {
            tick_rate_ms: 16,
            target_fps: 60,
            ..Default::default()
        }
    }

    /// Create a power-saving config (30fps, slow tick).
    #[must_use]
    pub fn power_saving() -> Self {
        Self {
            tick_rate_ms: 100,
            target_fps: 30,
            ..Default::default()
        }
    }
}

/// Frame timing metrics.
#[derive(Debug, Clone, Default)]
pub struct FrameMetrics {
    /// Time spent in verification phase.
    pub verify_time: Duration,
    /// Time spent in measure phase.
    pub measure_time: Duration,
    /// Time spent in layout phase.
    pub layout_time: Duration,
    /// Time spent in paint phase.
    pub paint_time: Duration,
    /// Total frame time.
    pub total_time: Duration,
    /// Frame number.
    pub frame_count: u64,
}

/// Main TUI application runner.
pub struct TuiApp<W: Widget> {
    root: W,
    config: TuiConfig,
    input_handler: InputHandler,
    metrics: FrameMetrics,
    should_quit: bool,
    color_mode: ColorMode,
}

/// Internal app runner that accepts a Terminal implementation.
struct AppRunner<'a, W: Widget, T: Terminal> {
    app: &'a mut TuiApp<W>,
    terminal: T,
    buffer: CellBuffer,
    renderer: DiffRenderer,
}

impl<W: Widget, T: Terminal> AppRunner<'_, W, T> {
    fn run_loop(&mut self) -> Result<(), TuiError> {
        let tick_duration = Duration::from_millis(self.app.config.tick_rate_ms);

        loop {
            let frame_start = Instant::now();

            // Check for terminal resize
            let (width, height) = self.terminal.size()?;
            if width != self.buffer.width() || height != self.buffer.height() {
                self.buffer.resize(width, height);
                self.renderer.reset();
            }

            // Phase 1: Verify (Jidoka gate)
            let verify_start = Instant::now();
            if !self.app.config.skip_verification {
                let verification = self.app.root.verify();
                if !verification.is_valid() {
                    return Err(TuiError::VerificationFailed(VerificationError::from(
                        verification,
                    )));
                }
            }
            self.app.metrics.verify_time = verify_start.elapsed();

            // Phase 2: Render frame
            self.app.render_frame(&mut self.buffer);

            // Phase 3: Flush to terminal
            self.terminal.flush(&mut self.buffer, &mut self.renderer)?;

            self.app.metrics.total_time = frame_start.elapsed();
            self.app.metrics.frame_count += 1;

            // Phase 4: Handle input
            if self.terminal.poll(tick_duration)? {
                if let CrosstermEvent::Key(key) = self.terminal.read_event()? {
                    if key.code == KeyCode::Char('q')
                        || key.code == KeyCode::Char('c')
                            && key
                                .modifiers
                                .contains(crossterm::event::KeyModifiers::CONTROL)
                    {
                        self.app.should_quit = true;
                    }

                    if let Some(event) = self.app.input_handler.convert(CrosstermEvent::Key(key)) {
                        let _ = self.app.root.event(&event);
                    }
                }
            }

            if self.app.should_quit {
                break;
            }
        }

        Ok(())
    }
}

impl<W: Widget> TuiApp<W> {
    /// Create a new TUI application with the given root widget.
    pub fn new(root: W) -> Result<Self, TuiError> {
        // Jidoka: reject Bricks with no assertions
        if root.assertions().is_empty() {
            return Err(TuiError::InvalidBrick(
                "Root widget has no assertions - every Brick must have at least one falsifiable assertion".to_string(),
            ));
        }

        Ok(Self {
            root,
            config: TuiConfig::default(),
            input_handler: InputHandler::new(),
            metrics: FrameMetrics::default(),
            should_quit: false,
            color_mode: ColorMode::detect(),
        })
    }

    /// Set the configuration.
    #[must_use]
    pub fn with_config(mut self, config: TuiConfig) -> Self {
        if let Some(mode) = config.color_mode {
            self.color_mode = mode;
        }
        self.config = config;
        self
    }

    /// Set the input handler.
    #[must_use]
    pub fn with_input_handler(mut self, handler: InputHandler) -> Self {
        self.input_handler = handler;
        self
    }

    /// Get a reference to the root widget.
    #[must_use]
    pub fn root(&self) -> &W {
        &self.root
    }

    /// Get a mutable reference to the root widget.
    pub fn root_mut(&mut self) -> &mut W {
        &mut self.root
    }

    /// Get the current frame metrics.
    #[must_use]
    pub fn metrics(&self) -> &FrameMetrics {
        &self.metrics
    }

    /// Request the application to quit.
    pub fn quit(&mut self) {
        self.should_quit = true;
    }

    /// Run the application (blocking).
    pub fn run(&mut self) -> Result<(), TuiError> {
        let backend = CrosstermBackend::new();
        let terminal = GenericTerminal::new(backend);
        self.run_with_terminal(terminal)
    }

    /// Run the application with a custom terminal implementation.
    /// This is the testable entry point.
    pub fn run_with_terminal<T: Terminal>(&mut self, mut terminal: T) -> Result<(), TuiError> {
        terminal.enter()?;

        if self.config.enable_mouse {
            terminal.enable_mouse()?;
        }

        // Get initial terminal size
        let (width, height) = terminal.size()?;
        let buffer = CellBuffer::new(width, height);
        let renderer = DiffRenderer::with_color_mode(self.color_mode);

        let mut runner = AppRunner {
            app: self,
            terminal,
            buffer,
            renderer,
        };

        let result = runner.run_loop();

        if runner.app.config.enable_mouse {
            runner.terminal.disable_mouse()?;
        }
        runner.terminal.leave()?;

        result
    }

    fn render_frame(&mut self, buffer: &mut CellBuffer) {
        let width = buffer.width();
        let height = buffer.height();

        // Phase 2a: Measure
        let measure_start = Instant::now();
        let constraints = Constraints::new(0.0, f32::from(width), 0.0, f32::from(height));
        let _size = self.root.measure(constraints);
        self.metrics.measure_time = measure_start.elapsed();

        // Phase 2b: Layout
        let layout_start = Instant::now();
        let bounds = Rect::new(0.0, 0.0, f32::from(width), f32::from(height));
        let _ = self.root.layout(bounds);
        self.metrics.layout_time = layout_start.elapsed();

        // Phase 2c: Paint
        let paint_start = Instant::now();
        {
            let mut canvas = DirectTerminalCanvas::new(buffer);
            self.root.paint(&mut canvas);
        }
        self.metrics.paint_time = paint_start.elapsed();
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use presentar_core::{
        Brick, BrickAssertion, BrickBudget, BrickVerification, Canvas, Color, Event, LayoutResult,
        Size, TypeId,
    };
    use std::any::Any;
    use std::time::Duration;

    struct TestWidget {
        assertions: Vec<BrickAssertion>,
    }

    impl TestWidget {
        fn new() -> Self {
            Self {
                assertions: vec![BrickAssertion::max_latency_ms(16)],
            }
        }

        fn without_assertions() -> Self {
            Self { assertions: vec![] }
        }
    }

    impl Brick for TestWidget {
        fn brick_name(&self) -> &'static str {
            "test_widget"
        }

        fn assertions(&self) -> &[BrickAssertion] {
            &self.assertions
        }

        fn budget(&self) -> BrickBudget {
            BrickBudget::default()
        }

        fn verify(&self) -> BrickVerification {
            BrickVerification {
                passed: self.assertions.clone(),
                failed: vec![],
                verification_time: Duration::from_micros(10),
            }
        }

        fn to_html(&self) -> String {
            String::new()
        }

        fn to_css(&self) -> String {
            String::new()
        }
    }

    impl Widget for TestWidget {
        fn type_id(&self) -> TypeId {
            TypeId::of::<Self>()
        }

        fn measure(&self, constraints: Constraints) -> Size {
            constraints.constrain(Size::new(10.0, 5.0))
        }

        fn layout(&mut self, bounds: Rect) -> LayoutResult {
            LayoutResult {
                size: Size::new(bounds.width, bounds.height),
            }
        }

        fn paint(&self, canvas: &mut dyn Canvas) {
            canvas.fill_rect(Rect::new(0.0, 0.0, 10.0, 5.0), Color::BLUE);
        }

        fn event(&mut self, _event: &Event) -> Option<Box<dyn Any + Send>> {
            None
        }

        fn children(&self) -> &[Box<dyn Widget>] {
            &[]
        }

        fn children_mut(&mut self) -> &mut [Box<dyn Widget>] {
            &mut []
        }
    }

    #[test]
    fn test_tui_app_creation() {
        let widget = TestWidget::new();
        let app = TuiApp::new(widget);
        assert!(app.is_ok());
    }

    #[test]
    fn test_tui_app_rejects_empty_assertions() {
        let widget = TestWidget::without_assertions();
        let app = TuiApp::new(widget);
        assert!(app.is_err());
        let err = app.err().expect("expected error");
        assert!(matches!(err, TuiError::InvalidBrick(_)));
    }

    #[test]
    fn test_config_default() {
        let config = TuiConfig::default();
        assert_eq!(config.tick_rate_ms, 250);
        assert_eq!(config.target_fps, 60);
        assert!(!config.enable_mouse);
        assert!(!config.skip_verification);
        assert!(config.color_mode.is_none());
    }

    #[test]
    fn test_config_high_performance() {
        let config = TuiConfig::high_performance();
        assert_eq!(config.tick_rate_ms, 16);
        assert_eq!(config.target_fps, 60);
    }

    #[test]
    fn test_config_power_saving() {
        let config = TuiConfig::power_saving();
        assert_eq!(config.tick_rate_ms, 100);
        assert_eq!(config.target_fps, 30);
    }

    #[test]
    fn test_tui_app_with_config() {
        let widget = TestWidget::new();
        let mut app = TuiApp::new(widget).unwrap();

        let config = TuiConfig {
            tick_rate_ms: 50,
            enable_mouse: true,
            color_mode: Some(ColorMode::Color256),
            skip_verification: false,
            target_fps: 30,
        };

        app = app.with_config(config);
        assert!(app.metrics().frame_count == 0);
    }

    #[test]
    fn test_tui_app_with_input_handler() {
        let widget = TestWidget::new();
        let mut app = TuiApp::new(widget).unwrap();

        let mut handler = InputHandler::new();
        handler.add_binding(crate::input::KeyBinding::simple(
            crossterm::event::KeyCode::Char('q'),
            "quit",
        ));

        app = app.with_input_handler(handler);
        assert!(app.root().assertions().len() == 1);
    }

    #[test]
    fn test_tui_app_root_accessors() {
        let widget = TestWidget::new();
        let mut app = TuiApp::new(widget).unwrap();

        assert_eq!(app.root().brick_name(), "test_widget");
        assert_eq!(app.root_mut().brick_name(), "test_widget");
    }

    #[test]
    fn test_tui_app_metrics() {
        let widget = TestWidget::new();
        let app = TuiApp::new(widget).unwrap();

        let metrics = app.metrics();
        assert_eq!(metrics.frame_count, 0);
        assert_eq!(metrics.total_time, Duration::ZERO);
    }

    #[test]
    fn test_tui_app_quit() {
        let widget = TestWidget::new();
        let mut app = TuiApp::new(widget).unwrap();

        assert!(!app.should_quit);
        app.quit();
        assert!(app.should_quit);
    }

    #[test]
    fn test_frame_metrics_default() {
        let metrics = FrameMetrics::default();
        assert_eq!(metrics.frame_count, 0);
        assert_eq!(metrics.verify_time, Duration::ZERO);
        assert_eq!(metrics.measure_time, Duration::ZERO);
        assert_eq!(metrics.layout_time, Duration::ZERO);
        assert_eq!(metrics.paint_time, Duration::ZERO);
        assert_eq!(metrics.total_time, Duration::ZERO);
    }

    #[test]
    fn test_config_with_color_mode_override() {
        let widget = TestWidget::new();
        let app = TuiApp::new(widget).unwrap();

        let config = TuiConfig {
            color_mode: Some(ColorMode::Mono),
            ..Default::default()
        };

        let app = app.with_config(config);
        assert_eq!(app.color_mode, ColorMode::Mono);
    }

    #[test]
    fn test_config_without_color_mode() {
        let widget = TestWidget::new();
        let app = TuiApp::new(widget).unwrap();
        let original_mode = app.color_mode;

        let config = TuiConfig {
            color_mode: None,
            ..Default::default()
        };

        let app = app.with_config(config);
        assert_eq!(app.color_mode, original_mode);
    }

    #[test]
    fn test_render_frame() {
        let widget = TestWidget::new();
        let mut app = TuiApp::new(widget).unwrap();
        let mut buffer = CellBuffer::new(80, 24);

        // Render a frame and verify metrics are updated
        app.render_frame(&mut buffer);

        assert!(
            app.metrics.measure_time > Duration::ZERO || app.metrics.measure_time == Duration::ZERO
        );
        assert!(app.metrics.layout_time >= Duration::ZERO);
        assert!(app.metrics.paint_time >= Duration::ZERO);
    }

    #[test]
    fn test_render_frame_updates_metrics() {
        let widget = TestWidget::new();
        let mut app = TuiApp::new(widget).unwrap();
        let mut buffer = CellBuffer::new(40, 10);

        // Render multiple frames
        for _ in 0..3 {
            app.render_frame(&mut buffer);
        }

        // Metrics should be set (even if durations are very small)
        let metrics = app.metrics();
        assert_eq!(metrics.frame_count, 0); // frame_count is only updated in run_loop
    }

    #[test]
    fn test_render_frame_with_different_buffer_sizes() {
        let widget = TestWidget::new();
        let mut app = TuiApp::new(widget).unwrap();

        // Small buffer
        let mut small_buffer = CellBuffer::new(10, 5);
        app.render_frame(&mut small_buffer);

        // Large buffer
        let mut large_buffer = CellBuffer::new(200, 50);
        app.render_frame(&mut large_buffer);

        // Should not panic with any buffer size
    }

    #[test]
    fn test_frame_metrics_clone() {
        let metrics = FrameMetrics {
            verify_time: Duration::from_millis(1),
            measure_time: Duration::from_millis(2),
            layout_time: Duration::from_millis(3),
            paint_time: Duration::from_millis(4),
            total_time: Duration::from_millis(10),
            frame_count: 100,
        };

        let cloned = metrics.clone();
        assert_eq!(cloned.frame_count, 100);
        assert_eq!(cloned.verify_time, Duration::from_millis(1));
    }

    #[test]
    fn test_frame_metrics_debug() {
        let metrics = FrameMetrics::default();
        let debug_str = format!("{:?}", metrics);
        assert!(debug_str.contains("FrameMetrics"));
        assert!(debug_str.contains("frame_count"));
    }

    #[test]
    fn test_tui_config_clone() {
        let config = TuiConfig::high_performance();
        let cloned = config.clone();
        assert_eq!(cloned.tick_rate_ms, 16);
        assert_eq!(cloned.target_fps, 60);
    }

    #[test]
    fn test_tui_config_debug() {
        let config = TuiConfig::default();
        let debug_str = format!("{:?}", config);
        assert!(debug_str.contains("TuiConfig"));
        assert!(debug_str.contains("tick_rate_ms"));
    }

    // Additional tests for improved coverage

    struct FailingWidget;

    impl Brick for FailingWidget {
        fn brick_name(&self) -> &'static str {
            "failing_widget"
        }

        fn assertions(&self) -> &[BrickAssertion] {
            static ASSERTIONS: &[BrickAssertion] = &[BrickAssertion::max_latency_ms(16)];
            ASSERTIONS
        }

        fn budget(&self) -> BrickBudget {
            BrickBudget::default()
        }

        fn verify(&self) -> BrickVerification {
            // This widget always fails verification
            BrickVerification {
                passed: vec![],
                failed: vec![(
                    BrickAssertion::max_latency_ms(16),
                    "Intentional failure".to_string(),
                )],
                verification_time: Duration::from_micros(10),
            }
        }

        fn to_html(&self) -> String {
            String::new()
        }

        fn to_css(&self) -> String {
            String::new()
        }
    }

    impl Widget for FailingWidget {
        fn type_id(&self) -> TypeId {
            TypeId::of::<Self>()
        }

        fn measure(&self, constraints: Constraints) -> Size {
            constraints.constrain(Size::new(10.0, 5.0))
        }

        fn layout(&mut self, bounds: Rect) -> LayoutResult {
            LayoutResult {
                size: Size::new(bounds.width, bounds.height),
            }
        }

        fn paint(&self, _canvas: &mut dyn Canvas) {}

        fn event(&mut self, _event: &Event) -> Option<Box<dyn Any + Send>> {
            None
        }

        fn children(&self) -> &[Box<dyn Widget>] {
            &[]
        }

        fn children_mut(&mut self) -> &mut [Box<dyn Widget>] {
            &mut []
        }
    }

    #[test]
    fn test_tui_app_with_failing_widget() {
        let widget = FailingWidget;
        let app = TuiApp::new(widget);
        // Should be Ok since we only check assertions on creation, not verify()
        assert!(app.is_ok());
    }

    #[test]
    fn test_tui_config_all_fields() {
        let config = TuiConfig {
            tick_rate_ms: 100,
            enable_mouse: true,
            color_mode: Some(ColorMode::Color16),
            skip_verification: true,
            target_fps: 30,
        };

        assert_eq!(config.tick_rate_ms, 100);
        assert!(config.enable_mouse);
        assert_eq!(config.color_mode, Some(ColorMode::Color16));
        assert!(config.skip_verification);
        assert_eq!(config.target_fps, 30);
    }

    #[test]
    fn test_frame_metrics_all_fields() {
        let metrics = FrameMetrics {
            verify_time: Duration::from_millis(1),
            measure_time: Duration::from_millis(2),
            layout_time: Duration::from_millis(3),
            paint_time: Duration::from_millis(4),
            total_time: Duration::from_millis(10),
            frame_count: 42,
        };

        assert_eq!(metrics.verify_time, Duration::from_millis(1));
        assert_eq!(metrics.measure_time, Duration::from_millis(2));
        assert_eq!(metrics.layout_time, Duration::from_millis(3));
        assert_eq!(metrics.paint_time, Duration::from_millis(4));
        assert_eq!(metrics.total_time, Duration::from_millis(10));
        assert_eq!(metrics.frame_count, 42);
    }

    #[test]
    fn test_tui_app_skip_verification_config() {
        let widget = TestWidget::new();
        let app = TuiApp::new(widget).unwrap();

        let config = TuiConfig {
            skip_verification: true,
            ..Default::default()
        };

        let app = app.with_config(config);
        assert!(app.config.skip_verification);
    }

    #[test]
    fn test_tui_app_enable_mouse_config() {
        let widget = TestWidget::new();
        let app = TuiApp::new(widget).unwrap();

        let config = TuiConfig {
            enable_mouse: true,
            ..Default::default()
        };

        let app = app.with_config(config);
        assert!(app.config.enable_mouse);
    }

    #[test]
    fn test_render_frame_zero_size_buffer() {
        let widget = TestWidget::new();
        let mut app = TuiApp::new(widget).unwrap();

        // Test with minimal buffer size
        let mut buffer = CellBuffer::new(1, 1);
        app.render_frame(&mut buffer);
        // Should not panic
    }

    #[test]
    fn test_render_frame_metrics_populated() {
        let widget = TestWidget::new();
        let mut app = TuiApp::new(widget).unwrap();
        let mut buffer = CellBuffer::new(80, 24);

        app.render_frame(&mut buffer);

        // All timing metrics should be non-negative (possibly zero for fast operations)
        assert!(app.metrics.measure_time >= Duration::ZERO);
        assert!(app.metrics.layout_time >= Duration::ZERO);
        assert!(app.metrics.paint_time >= Duration::ZERO);
    }

    #[test]
    fn test_tui_config_color_modes() {
        // Test all color modes
        for mode in [
            ColorMode::TrueColor,
            ColorMode::Color256,
            ColorMode::Color16,
            ColorMode::Mono,
        ] {
            let widget = TestWidget::new();
            let app = TuiApp::new(widget).unwrap();

            let config = TuiConfig {
                color_mode: Some(mode),
                ..Default::default()
            };

            let app = app.with_config(config);
            assert_eq!(app.color_mode, mode);
        }
    }

    #[test]
    fn test_test_widget_brick_methods() {
        let widget = TestWidget::new();

        assert_eq!(widget.brick_name(), "test_widget");
        assert!(!widget.assertions().is_empty());
        assert!(widget.verify().is_valid());
        assert!(widget.to_html().is_empty());
        assert!(widget.to_css().is_empty());
    }

    #[test]
    fn test_test_widget_widget_methods() {
        let mut widget = TestWidget::new();

        // measure
        let size = widget.measure(Constraints::loose(Size::new(100.0, 100.0)));
        assert!(size.width > 0.0);
        assert!(size.height > 0.0);

        // layout
        let bounds = Rect::new(0.0, 0.0, 50.0, 25.0);
        let result = widget.layout(bounds);
        assert_eq!(result.size.width, 50.0);
        assert_eq!(result.size.height, 25.0);

        // event
        let event = Event::KeyDown {
            key: presentar_core::Key::Enter,
        };
        assert!(widget.event(&event).is_none());

        // children
        assert!(widget.children().is_empty());
        assert!(widget.children_mut().is_empty());
    }

    #[test]
    fn test_tui_app_multiple_render_frames() {
        let widget = TestWidget::new();
        let mut app = TuiApp::new(widget).unwrap();
        let mut buffer = CellBuffer::new(80, 24);

        // Render multiple frames to ensure stability
        for _ in 0..10 {
            app.render_frame(&mut buffer);
        }

        // Should complete without panic
    }

    // Mock terminal for testing run/run_loop

    use std::cell::RefCell;
    use std::collections::VecDeque;

    struct MockTerminal {
        size: (u16, u16),
        events: RefCell<VecDeque<CrosstermEvent>>,
        poll_results: RefCell<VecDeque<bool>>,
        entered: RefCell<bool>,
        left: RefCell<bool>,
        mouse_enabled: RefCell<bool>,
        flush_count: RefCell<u32>,
    }

    impl MockTerminal {
        fn new(width: u16, height: u16) -> Self {
            Self {
                size: (width, height),
                events: RefCell::new(VecDeque::new()),
                poll_results: RefCell::new(VecDeque::new()),
                entered: RefCell::new(false),
                left: RefCell::new(false),
                mouse_enabled: RefCell::new(false),
                flush_count: RefCell::new(0),
            }
        }

        fn with_events(mut self, events: Vec<CrosstermEvent>) -> Self {
            self.events = RefCell::new(events.into());
            self
        }

        fn with_polls(mut self, polls: Vec<bool>) -> Self {
            self.poll_results = RefCell::new(polls.into());
            self
        }
    }

    impl Terminal for MockTerminal {
        fn enter(&mut self) -> Result<(), TuiError> {
            *self.entered.borrow_mut() = true;
            Ok(())
        }

        fn leave(&mut self) -> Result<(), TuiError> {
            *self.left.borrow_mut() = true;
            Ok(())
        }

        fn size(&self) -> Result<(u16, u16), TuiError> {
            Ok(self.size)
        }

        fn poll(&self, _timeout: Duration) -> Result<bool, TuiError> {
            Ok(self.poll_results.borrow_mut().pop_front().unwrap_or(false))
        }

        fn read_event(&self) -> Result<CrosstermEvent, TuiError> {
            self.events
                .borrow_mut()
                .pop_front()
                .ok_or_else(|| TuiError::Io(io::Error::new(io::ErrorKind::Other, "no event")))
        }

        fn flush(
            &mut self,
            _buffer: &mut CellBuffer,
            _renderer: &mut DiffRenderer,
        ) -> Result<(), TuiError> {
            *self.flush_count.borrow_mut() += 1;
            Ok(())
        }

        fn enable_mouse(&mut self) -> Result<(), TuiError> {
            *self.mouse_enabled.borrow_mut() = true;
            Ok(())
        }

        fn disable_mouse(&mut self) -> Result<(), TuiError> {
            *self.mouse_enabled.borrow_mut() = false;
            Ok(())
        }
    }

    #[test]
    fn test_run_with_terminal_quit_on_q() {
        let widget = TestWidget::new();
        let mut app = TuiApp::new(widget).unwrap();

        let terminal = MockTerminal::new(80, 24)
            .with_polls(vec![true])
            .with_events(vec![CrosstermEvent::Key(crossterm::event::KeyEvent::new(
                KeyCode::Char('q'),
                crossterm::event::KeyModifiers::NONE,
            ))]);

        let result = app.run_with_terminal(terminal);
        assert!(result.is_ok());
        assert!(app.should_quit);
    }

    #[test]
    fn test_run_with_terminal_ctrl_c() {
        let widget = TestWidget::new();
        let mut app = TuiApp::new(widget).unwrap();

        let terminal = MockTerminal::new(80, 24)
            .with_polls(vec![true])
            .with_events(vec![CrosstermEvent::Key(crossterm::event::KeyEvent::new(
                KeyCode::Char('c'),
                crossterm::event::KeyModifiers::CONTROL,
            ))]);

        let result = app.run_with_terminal(terminal);
        assert!(result.is_ok());
        assert!(app.should_quit);
    }

    #[test]
    fn test_run_with_terminal_mouse_enabled() {
        let widget = TestWidget::new();
        let mut app = TuiApp::new(widget).unwrap();
        app.config.enable_mouse = true;

        let terminal = MockTerminal::new(80, 24)
            .with_polls(vec![true])
            .with_events(vec![CrosstermEvent::Key(crossterm::event::KeyEvent::new(
                KeyCode::Char('q'),
                crossterm::event::KeyModifiers::NONE,
            ))]);

        let result = app.run_with_terminal(terminal);
        assert!(result.is_ok());
    }

    #[test]
    fn test_run_with_terminal_skip_verification() {
        let widget = FailingWidget;
        let mut app = TuiApp::new(widget).unwrap();
        app.config.skip_verification = true;

        let terminal = MockTerminal::new(80, 24)
            .with_polls(vec![true])
            .with_events(vec![CrosstermEvent::Key(crossterm::event::KeyEvent::new(
                KeyCode::Char('q'),
                crossterm::event::KeyModifiers::NONE,
            ))]);

        // Should succeed because verification is skipped
        let result = app.run_with_terminal(terminal);
        assert!(result.is_ok());
    }

    #[test]
    fn test_run_with_terminal_verification_failure() {
        let widget = FailingWidget;
        let mut app = TuiApp::new(widget).unwrap();

        let terminal = MockTerminal::new(80, 24).with_polls(vec![false]);

        // Should fail verification
        let result = app.run_with_terminal(terminal);
        assert!(result.is_err());
        assert!(matches!(result, Err(TuiError::VerificationFailed(_))));
    }

    #[test]
    fn test_run_with_terminal_no_events() {
        let widget = TestWidget::new();
        let mut app = TuiApp::new(widget).unwrap();
        app.quit(); // Pre-set quit to exit immediately

        let terminal = MockTerminal::new(80, 24).with_polls(vec![false]);

        let result = app.run_with_terminal(terminal);
        assert!(result.is_ok());
    }

    #[test]
    fn test_run_with_terminal_other_key() {
        let widget = TestWidget::new();
        let mut app = TuiApp::new(widget).unwrap();

        let terminal = MockTerminal::new(80, 24)
            .with_polls(vec![true, true])
            .with_events(vec![
                CrosstermEvent::Key(crossterm::event::KeyEvent::new(
                    KeyCode::Enter,
                    crossterm::event::KeyModifiers::NONE,
                )),
                CrosstermEvent::Key(crossterm::event::KeyEvent::new(
                    KeyCode::Char('q'),
                    crossterm::event::KeyModifiers::NONE,
                )),
            ]);

        let result = app.run_with_terminal(terminal);
        assert!(result.is_ok());
    }

    #[test]
    fn test_run_with_terminal_frame_count() {
        let widget = TestWidget::new();
        let mut app = TuiApp::new(widget).unwrap();

        let terminal = MockTerminal::new(80, 24)
            .with_polls(vec![false, false, true])
            .with_events(vec![CrosstermEvent::Key(crossterm::event::KeyEvent::new(
                KeyCode::Char('q'),
                crossterm::event::KeyModifiers::NONE,
            ))]);

        let result = app.run_with_terminal(terminal);
        assert!(result.is_ok());
        assert!(app.metrics.frame_count >= 1);
    }

    #[test]
    fn test_crossterm_backend_new() {
        let backend = CrosstermBackend::new();
        // Just verify it can be created
        let _ = backend;
    }

    #[test]
    fn test_crossterm_backend_default() {
        let backend = CrosstermBackend::default();
        let _ = backend;
    }

    // Mock backend for testing GenericTerminal
    struct MockBackend {
        size: (u16, u16),
        events: RefCell<VecDeque<CrosstermEvent>>,
        poll_results: RefCell<VecDeque<bool>>,
        raw_mode: RefCell<bool>,
        alternate_screen: RefCell<bool>,
        cursor_hidden: RefCell<bool>,
        mouse_captured: RefCell<bool>,
    }

    impl MockBackend {
        fn new(width: u16, height: u16) -> Self {
            Self {
                size: (width, height),
                events: RefCell::new(VecDeque::new()),
                poll_results: RefCell::new(VecDeque::new()),
                raw_mode: RefCell::new(false),
                alternate_screen: RefCell::new(false),
                cursor_hidden: RefCell::new(false),
                mouse_captured: RefCell::new(false),
            }
        }

        fn with_events(self, events: Vec<CrosstermEvent>) -> Self {
            *self.events.borrow_mut() = events.into();
            self
        }

        fn with_polls(self, polls: Vec<bool>) -> Self {
            *self.poll_results.borrow_mut() = polls.into();
            self
        }
    }

    impl TerminalBackend for MockBackend {
        fn enable_raw_mode(&mut self) -> Result<(), TuiError> {
            *self.raw_mode.borrow_mut() = true;
            Ok(())
        }
        fn disable_raw_mode(&mut self) -> Result<(), TuiError> {
            *self.raw_mode.borrow_mut() = false;
            Ok(())
        }
        fn enter_alternate_screen(&mut self) -> Result<(), TuiError> {
            *self.alternate_screen.borrow_mut() = true;
            Ok(())
        }
        fn leave_alternate_screen(&mut self) -> Result<(), TuiError> {
            *self.alternate_screen.borrow_mut() = false;
            Ok(())
        }
        fn hide_cursor(&mut self) -> Result<(), TuiError> {
            *self.cursor_hidden.borrow_mut() = true;
            Ok(())
        }
        fn show_cursor(&mut self) -> Result<(), TuiError> {
            *self.cursor_hidden.borrow_mut() = false;
            Ok(())
        }
        fn size(&self) -> Result<(u16, u16), TuiError> {
            Ok(self.size)
        }
        fn poll(&self, _timeout: Duration) -> Result<bool, TuiError> {
            Ok(self.poll_results.borrow_mut().pop_front().unwrap_or(false))
        }
        fn read_event(&self) -> Result<CrosstermEvent, TuiError> {
            self.events
                .borrow_mut()
                .pop_front()
                .ok_or_else(|| TuiError::Io(io::Error::new(io::ErrorKind::Other, "no event")))
        }
        fn write_flush(
            &mut self,
            _buffer: &mut CellBuffer,
            _renderer: &mut DiffRenderer,
        ) -> Result<(), TuiError> {
            Ok(())
        }
        fn enable_mouse_capture(&mut self) -> Result<(), TuiError> {
            *self.mouse_captured.borrow_mut() = true;
            Ok(())
        }
        fn disable_mouse_capture(&mut self) -> Result<(), TuiError> {
            *self.mouse_captured.borrow_mut() = false;
            Ok(())
        }
    }

    #[test]
    fn test_generic_terminal_enter_leave() {
        let backend = MockBackend::new(80, 24);
        let mut terminal = GenericTerminal::new(backend);

        terminal.enter().unwrap();
        assert!(*terminal.backend.raw_mode.borrow());
        assert!(*terminal.backend.alternate_screen.borrow());
        assert!(*terminal.backend.cursor_hidden.borrow());

        terminal.leave().unwrap();
        assert!(!*terminal.backend.raw_mode.borrow());
        assert!(!*terminal.backend.alternate_screen.borrow());
        assert!(!*terminal.backend.cursor_hidden.borrow());
    }

    #[test]
    fn test_generic_terminal_size() {
        let backend = MockBackend::new(100, 50);
        let terminal = GenericTerminal::new(backend);
        let (w, h) = terminal.size().unwrap();
        assert_eq!(w, 100);
        assert_eq!(h, 50);
    }

    #[test]
    fn test_generic_terminal_poll_read() {
        let backend = MockBackend::new(80, 24)
            .with_polls(vec![true, false])
            .with_events(vec![CrosstermEvent::Key(crossterm::event::KeyEvent::new(
                KeyCode::Enter,
                crossterm::event::KeyModifiers::NONE,
            ))]);
        let terminal = GenericTerminal::new(backend);

        assert!(terminal.poll(Duration::from_millis(10)).unwrap());
        let event = terminal.read_event().unwrap();
        assert!(matches!(event, CrosstermEvent::Key(_)));

        assert!(!terminal.poll(Duration::from_millis(10)).unwrap());
    }

    #[test]
    fn test_generic_terminal_mouse() {
        let backend = MockBackend::new(80, 24);
        let mut terminal = GenericTerminal::new(backend);

        assert!(!*terminal.backend.mouse_captured.borrow());
        terminal.enable_mouse().unwrap();
        assert!(*terminal.backend.mouse_captured.borrow());
        terminal.disable_mouse().unwrap();
        assert!(!*terminal.backend.mouse_captured.borrow());
    }

    #[test]
    fn test_generic_terminal_flush() {
        let backend = MockBackend::new(80, 24);
        let mut terminal = GenericTerminal::new(backend);
        let mut buffer = CellBuffer::new(80, 24);
        let mut renderer = DiffRenderer::new();

        terminal.flush(&mut buffer, &mut renderer).unwrap();
    }

    #[test]
    fn test_run_with_generic_terminal() {
        let widget = TestWidget::new();
        let mut app = TuiApp::new(widget).unwrap();

        let backend = MockBackend::new(80, 24)
            .with_polls(vec![true])
            .with_events(vec![CrosstermEvent::Key(crossterm::event::KeyEvent::new(
                KeyCode::Char('q'),
                crossterm::event::KeyModifiers::NONE,
            ))]);
        let terminal = GenericTerminal::new(backend);

        let result = app.run_with_terminal(terminal);
        assert!(result.is_ok());
        assert!(app.should_quit);
    }

    #[test]
    fn test_mock_terminal_enter_leave() {
        let mut terminal = MockTerminal::new(80, 24);
        assert!(!*terminal.entered.borrow());
        terminal.enter().unwrap();
        assert!(*terminal.entered.borrow());

        assert!(!*terminal.left.borrow());
        terminal.leave().unwrap();
        assert!(*terminal.left.borrow());
    }

    #[test]
    fn test_mock_terminal_mouse() {
        let mut terminal = MockTerminal::new(80, 24);
        assert!(!*terminal.mouse_enabled.borrow());
        terminal.enable_mouse().unwrap();
        assert!(*terminal.mouse_enabled.borrow());
        terminal.disable_mouse().unwrap();
        assert!(!*terminal.mouse_enabled.borrow());
    }

    #[test]
    fn test_mock_terminal_size() {
        let terminal = MockTerminal::new(100, 50);
        let (w, h) = terminal.size().unwrap();
        assert_eq!(w, 100);
        assert_eq!(h, 50);
    }

    #[test]
    fn test_run_with_terminal_resize() {
        let widget = TestWidget::new();
        let mut app = TuiApp::new(widget).unwrap();

        // Create terminal that simulates a size change by having different initial size
        let terminal = MockTerminal::new(40, 12)
            .with_polls(vec![true])
            .with_events(vec![CrosstermEvent::Key(crossterm::event::KeyEvent::new(
                KeyCode::Char('q'),
                crossterm::event::KeyModifiers::NONE,
            ))]);

        let result = app.run_with_terminal(terminal);
        assert!(result.is_ok());
    }

    #[test]
    fn test_run_with_terminal_mouse_event() {
        let widget = TestWidget::new();
        let mut app = TuiApp::new(widget).unwrap();

        let terminal = MockTerminal::new(80, 24)
            .with_polls(vec![true, true])
            .with_events(vec![
                CrosstermEvent::Mouse(crossterm::event::MouseEvent {
                    kind: crossterm::event::MouseEventKind::Down(
                        crossterm::event::MouseButton::Left,
                    ),
                    column: 10,
                    row: 5,
                    modifiers: crossterm::event::KeyModifiers::NONE,
                }),
                CrosstermEvent::Key(crossterm::event::KeyEvent::new(
                    KeyCode::Char('q'),
                    crossterm::event::KeyModifiers::NONE,
                )),
            ]);

        let result = app.run_with_terminal(terminal);
        assert!(result.is_ok());
    }

    #[test]
    fn test_run_with_terminal_non_key_event_then_quit() {
        let widget = TestWidget::new();
        let mut app = TuiApp::new(widget).unwrap();

        let terminal = MockTerminal::new(80, 24)
            .with_polls(vec![true, true])
            .with_events(vec![
                CrosstermEvent::Resize(100, 50),
                CrosstermEvent::Key(crossterm::event::KeyEvent::new(
                    KeyCode::Char('q'),
                    crossterm::event::KeyModifiers::NONE,
                )),
            ]);

        let result = app.run_with_terminal(terminal);
        assert!(result.is_ok());
    }

    #[test]
    fn test_app_runner_metrics_update() {
        let widget = TestWidget::new();
        let mut app = TuiApp::new(widget).unwrap();

        let terminal = MockTerminal::new(80, 24)
            .with_polls(vec![false, true])
            .with_events(vec![CrosstermEvent::Key(crossterm::event::KeyEvent::new(
                KeyCode::Char('q'),
                crossterm::event::KeyModifiers::NONE,
            ))]);

        app.run_with_terminal(terminal).unwrap();

        // Metrics should be populated
        assert!(app.metrics.frame_count >= 1);
    }

    // =====================================================
    // TestableBackend tests - TTY mocking with escape sequences
    // =====================================================

    #[test]
    fn test_testable_backend_new() {
        let buf: Vec<u8> = Vec::new();
        let backend = TestableBackend::new(buf, 80, 24);
        assert_eq!(backend.size, (80, 24));
        assert!(!backend.raw_mode);
        assert!(!backend.alternate_screen);
        assert!(!backend.cursor_hidden);
        assert!(!backend.mouse_captured);
    }

    #[test]
    fn test_testable_backend_with_events() {
        let buf: Vec<u8> = Vec::new();
        let backend = TestableBackend::new(buf, 80, 24).with_events(vec![CrosstermEvent::Key(
            crossterm::event::KeyEvent::new(
                KeyCode::Char('a'),
                crossterm::event::KeyModifiers::NONE,
            ),
        )]);
        assert_eq!(backend.events.borrow().len(), 1);
    }

    #[test]
    fn test_testable_backend_with_polls() {
        let buf: Vec<u8> = Vec::new();
        let backend = TestableBackend::new(buf, 80, 24).with_polls(vec![true, false, true]);
        assert_eq!(backend.poll_results.borrow().len(), 3);
    }

    #[test]
    fn test_testable_backend_enable_raw_mode() {
        let buf: Vec<u8> = Vec::new();
        let mut backend = TestableBackend::new(buf, 80, 24);
        assert!(!backend.is_raw_mode());
        backend.enable_raw_mode().unwrap();
        assert!(backend.is_raw_mode());
    }

    #[test]
    fn test_testable_backend_disable_raw_mode() {
        let buf: Vec<u8> = Vec::new();
        let mut backend = TestableBackend::new(buf, 80, 24);
        backend.enable_raw_mode().unwrap();
        assert!(backend.is_raw_mode());
        backend.disable_raw_mode().unwrap();
        assert!(!backend.is_raw_mode());
    }

    #[test]
    fn test_testable_backend_enter_alternate_screen() {
        let buf: Vec<u8> = Vec::new();
        let mut backend = TestableBackend::new(buf, 80, 24);
        assert!(!backend.is_alternate_screen());
        backend.enter_alternate_screen().unwrap();
        assert!(backend.is_alternate_screen());
        // Verify escape sequence was written
        let output = backend.into_writer();
        assert!(!output.is_empty());
        // EnterAlternateScreen is \x1b[?1049h
        assert!(output.starts_with(b"\x1b["));
    }

    #[test]
    fn test_testable_backend_leave_alternate_screen() {
        let buf: Vec<u8> = Vec::new();
        let mut backend = TestableBackend::new(buf, 80, 24);
        backend.enter_alternate_screen().unwrap();
        backend.leave_alternate_screen().unwrap();
        assert!(!backend.is_alternate_screen());
    }

    #[test]
    fn test_testable_backend_hide_cursor() {
        let buf: Vec<u8> = Vec::new();
        let mut backend = TestableBackend::new(buf, 80, 24);
        assert!(!backend.is_cursor_hidden());
        backend.hide_cursor().unwrap();
        assert!(backend.is_cursor_hidden());
        // Verify escape sequence was written
        let output = backend.into_writer();
        assert!(!output.is_empty());
    }

    #[test]
    fn test_testable_backend_show_cursor() {
        let buf: Vec<u8> = Vec::new();
        let mut backend = TestableBackend::new(buf, 80, 24);
        backend.hide_cursor().unwrap();
        backend.show_cursor().unwrap();
        assert!(!backend.is_cursor_hidden());
    }

    #[test]
    fn test_testable_backend_size() {
        let buf: Vec<u8> = Vec::new();
        let backend = TestableBackend::new(buf, 120, 40);
        assert_eq!(backend.size().unwrap(), (120, 40));
    }

    #[test]
    fn test_testable_backend_poll() {
        let buf: Vec<u8> = Vec::new();
        let backend = TestableBackend::new(buf, 80, 24).with_polls(vec![true, false]);
        assert!(backend.poll(Duration::from_millis(100)).unwrap());
        assert!(!backend.poll(Duration::from_millis(100)).unwrap());
        // Default when empty
        assert!(!backend.poll(Duration::from_millis(100)).unwrap());
    }

    #[test]
    fn test_testable_backend_read_event() {
        let buf: Vec<u8> = Vec::new();
        let backend = TestableBackend::new(buf, 80, 24).with_events(vec![CrosstermEvent::Key(
            crossterm::event::KeyEvent::new(
                KeyCode::Char('x'),
                crossterm::event::KeyModifiers::NONE,
            ),
        )]);
        let event = backend.read_event().unwrap();
        assert!(matches!(event, CrosstermEvent::Key(_)));
    }

    #[test]
    fn test_testable_backend_read_event_empty() {
        let buf: Vec<u8> = Vec::new();
        let backend = TestableBackend::new(buf, 80, 24);
        let result = backend.read_event();
        assert!(result.is_err());
    }

    #[test]
    fn test_testable_backend_enable_mouse_capture() {
        let buf: Vec<u8> = Vec::new();
        let mut backend = TestableBackend::new(buf, 80, 24);
        assert!(!backend.is_mouse_captured());
        backend.enable_mouse_capture().unwrap();
        assert!(backend.is_mouse_captured());
        // Verify escape sequence was written
        let output = backend.into_writer();
        assert!(!output.is_empty());
    }

    #[test]
    fn test_testable_backend_disable_mouse_capture() {
        let buf: Vec<u8> = Vec::new();
        let mut backend = TestableBackend::new(buf, 80, 24);
        backend.enable_mouse_capture().unwrap();
        backend.disable_mouse_capture().unwrap();
        assert!(!backend.is_mouse_captured());
    }

    #[test]
    fn test_testable_backend_write_flush() {
        use crate::direct::Cell;

        let buf: Vec<u8> = Vec::new();
        let mut backend = TestableBackend::new(buf, 80, 24);
        let mut buffer = CellBuffer::new(80, 24);
        let mut renderer = DiffRenderer::new();

        // Write something to the buffer using the Cell API
        let mut cell_a = Cell::default();
        cell_a.update(
            "A",
            presentar_core::Color::WHITE,
            presentar_core::Color::BLACK,
            crate::direct::Modifiers::empty(),
        );
        buffer.set(0, 0, cell_a);

        let mut cell_b = Cell::default();
        cell_b.update(
            "B",
            presentar_core::Color::WHITE,
            presentar_core::Color::BLACK,
            crate::direct::Modifiers::empty(),
        );
        buffer.set(1, 0, cell_b);

        buffer.mark_all_dirty();
        backend.write_flush(&mut buffer, &mut renderer).unwrap();

        // Verify output was written
        let output = backend.into_writer();
        assert!(!output.is_empty());
    }

    #[test]
    fn test_testable_backend_full_lifecycle() {
        let buf: Vec<u8> = Vec::new();
        let mut backend = TestableBackend::new(buf, 80, 24);

        // Enter
        backend.enable_raw_mode().unwrap();
        backend.enter_alternate_screen().unwrap();
        backend.hide_cursor().unwrap();

        assert!(backend.is_raw_mode());
        assert!(backend.is_alternate_screen());
        assert!(backend.is_cursor_hidden());

        // Leave
        backend.show_cursor().unwrap();
        backend.leave_alternate_screen().unwrap();
        backend.disable_raw_mode().unwrap();

        assert!(!backend.is_raw_mode());
        assert!(!backend.is_alternate_screen());
        assert!(!backend.is_cursor_hidden());
    }

    #[test]
    fn test_testable_backend_escape_sequences() {
        let buf: Vec<u8> = Vec::new();
        let mut backend = TestableBackend::new(buf, 80, 24);

        backend.enter_alternate_screen().unwrap();
        backend.hide_cursor().unwrap();
        backend.enable_mouse_capture().unwrap();

        let output = backend.into_writer();
        let output_str = String::from_utf8_lossy(&output);

        // Check for ANSI escape sequences (CSI = \x1b[)
        assert!(
            output_str.contains("\x1b["),
            "Expected ANSI escape sequences"
        );
    }

    #[test]
    fn test_generic_terminal_with_testable_backend() {
        let buf: Vec<u8> = Vec::new();
        let backend = TestableBackend::new(buf, 80, 24)
            .with_polls(vec![true])
            .with_events(vec![CrosstermEvent::Key(crossterm::event::KeyEvent::new(
                KeyCode::Char('q'),
                crossterm::event::KeyModifiers::NONE,
            ))]);

        let mut terminal = GenericTerminal::new(backend);

        terminal.enter().unwrap();
        assert_eq!(terminal.size().unwrap(), (80, 24));

        // Poll and read
        assert!(terminal.poll(Duration::from_millis(10)).unwrap());
        let event = terminal.read_event().unwrap();
        assert!(matches!(event, CrosstermEvent::Key(_)));

        terminal.leave().unwrap();
    }

    #[test]
    fn test_testable_backend_with_tui_app() {
        let widget = TestWidget::new();
        let mut app = TuiApp::new(widget).unwrap();

        let buf: Vec<u8> = Vec::new();
        let backend = TestableBackend::new(buf, 80, 24)
            .with_polls(vec![true])
            .with_events(vec![CrosstermEvent::Key(crossterm::event::KeyEvent::new(
                KeyCode::Char('q'),
                crossterm::event::KeyModifiers::NONE,
            ))]);

        let terminal = GenericTerminal::new(backend);
        let result = app.run_with_terminal(terminal);
        assert!(result.is_ok());
    }

    #[test]
    fn test_testable_backend_captures_render_output() {
        let widget = TestWidget::new();
        let _app = TuiApp::new(widget).unwrap();

        let buf: Vec<u8> = Vec::new();
        let backend = TestableBackend::new(buf, 40, 10)
            .with_polls(vec![true])
            .with_events(vec![CrosstermEvent::Key(crossterm::event::KeyEvent::new(
                KeyCode::Char('q'),
                crossterm::event::KeyModifiers::NONE,
            ))]);

        let mut terminal = GenericTerminal::new(backend);
        terminal.enter().unwrap();

        // Get terminal size
        let (width, height) = terminal.size().unwrap();
        assert_eq!((width, height), (40, 10));

        terminal.leave().unwrap();
    }
}