use crate::audio::HostAudio;
use crate::debugger::HostDebugger;
use crate::fs_backend::HostDirBackend;
use crate::input::HostInputHandler;
use crate::log_sink::HostConsoleSink;
use crate::overlay::{capture_snapshot, draw_overlay};
use crate::stats::HostStats;
use crate::utilities::draw_rgb565_to_rgba8;
use pixels::wgpu::PresentMode;
use pixels::{Pixels, PixelsBuilder, SurfaceTexture};
use prometeu_drivers::AudioCommand;
use prometeu_drivers::hardware::Hardware;
use prometeu_firmware::{BootTarget, Firmware};
use prometeu_hal::telemetry::CertificationConfig;
use std::time::{Duration, Instant};
use winit::application::ApplicationHandler;
use winit::dpi::LogicalSize;
use winit::event::{ElementState, WindowEvent};
use winit::event_loop::{ActiveEventLoop, ControlFlow};
use winit::keyboard::{KeyCode, PhysicalKey};
use winit::window::{Window, WindowAttributes, WindowId};

/// The Desktop implementation of the PROMETEU Runtime.
///
/// This struct acts as the physical "chassis" of the virtual console. It is
/// responsible for:
/// - Creating and managing the OS window (via `winit`).
/// - Initializing the GPU-accelerated framebuffer (via `pixels`).
/// - Handling real keyboard/gamepad events and converting them to virtual signals.
/// - Providing a high-fidelity audio backend (via `cpal`).
/// - Implementing the DevTools Protocol for remote debugging.
/// - Maintaining a deterministic 60Hz timing loop.
pub struct HostRunner {
    /// The OS window handle.
    window: Option<&'static Window>,
    /// The pixel buffer interface for rendering to the GPU.
    pixels: Option<Pixels<'static>>,

    /// The instance of the virtual hardware peripherals.
    hardware: Hardware,
    /// The instance of the system firmware and OS logic.
    firmware: Firmware,

    /// Helper to collect and normalize input signals.
    input: HostInputHandler,
    /// Root path for the virtual sandbox filesystem.
    fs_root: Option<String>,

    /// Sink for system and application logs (prints to console).
    log_sink: HostConsoleSink,

    /// Target duration for a single frame (nominally 16.66ms for 60Hz).
    frame_target_dt: Duration,
    /// Last recorded wall-clock time to calculate deltas.
    last_frame_time: Instant,
    /// Time accumulator used to guarantee exact 60Hz logic updates.
    accumulator: Duration,

    /// Performance metrics collector.
    stats: HostStats,
    /// Remote debugger interface.
    debugger: HostDebugger,

    /// Flag to enable/disable the technical telemetry display.
    overlay_enabled: bool,

    /// The physical audio driver.
    audio: HostAudio,
    /// Last known pause state to sync with audio.
    last_paused_state: bool,
}

impl HostRunner {
    /// Configures the boot target (Hub or specific Cartridge).
    pub(crate) fn set_boot_target(&mut self, boot_target: BootTarget) {
        self.firmware.boot_target = boot_target.clone();
        self.debugger.setup_boot_target(&boot_target, &mut self.firmware);
    }

    /// Creates a new desktop runner instance.
    pub(crate) fn new(fs_root: Option<String>, cap_config: Option<CertificationConfig>) -> Self {
        let target_fps = 60;

        let mut firmware = Firmware::new(cap_config);
        if let Some(root) = &fs_root {
            let backend = HostDirBackend::new(root);
            firmware.os.mount_fs(Box::new(backend));
        }

        Self {
            window: None,
            pixels: None,
            hardware: Hardware::new(),
            firmware,
            input: HostInputHandler::new(),
            fs_root,
            log_sink: HostConsoleSink::new(),
            frame_target_dt: Duration::from_nanos(1_000_000_000 / target_fps),
            last_frame_time: Instant::now(),
            accumulator: Duration::ZERO,

            stats: HostStats::new(),
            debugger: HostDebugger::new(),
            overlay_enabled: false,
            audio: HostAudio::new(),
            last_paused_state: false,
        }
    }

    fn window(&self) -> &'static Window {
        self.window.expect("window not created yet")
    }

    fn resize_surface(&mut self, width: u32, height: u32) {
        if let Some(p) = self.pixels.as_mut() {
            let _ = p.resize_surface(width, height);
        }
    }

    fn request_redraw(&self) {
        if let Some(w) = self.window.as_ref() {
            w.request_redraw();
        }
    }

}

impl ApplicationHandler for HostRunner {
    fn resumed(&mut self, event_loop: &ActiveEventLoop) {
        let attrs = WindowAttributes::default()
            .with_title(format!(
                "PROMETEU | GFX: {:.1} KB | FPS: {:.1} | Load: {:.1}% (C) + {:.1}% (A) | Frame: tick {} logical {} done {}",
                0.0, 0.0, 0.0, 0, 0, 0, 0))
            .with_inner_size(LogicalSize::new(960.0, 540.0))
            .with_min_inner_size(LogicalSize::new(320.0, 180.0));

        let window = event_loop.create_window(attrs).expect("failed to create window");

        // 🔥 Leak: Window becomes &'static Window (bootstrap)
        let window: &'static Window = Box::leak(Box::new(window));
        self.window = Some(window);

        let size = window.inner_size();
        let surface_texture = SurfaceTexture::new(size.width, size.height, window);

        let mut pixels =
            PixelsBuilder::new(Hardware::W as u32, Hardware::H as u32, surface_texture)
                .present_mode(PresentMode::Fifo) // activate vsync
                .build()
                .expect("failed to create Pixels");

        pixels.frame_mut().fill(0);

        self.pixels = Some(pixels);

        if let Err(err) = self.audio.init() {
            eprintln!("[HostAudio] Disabled: {}", err);
        }

        event_loop.set_control_flow(ControlFlow::Poll);
    }

    fn window_event(&mut self, event_loop: &ActiveEventLoop, _id: WindowId, event: WindowEvent) {
        self.input.handle_event(&event, self.window());

        match event {
            WindowEvent::CloseRequested => event_loop.exit(),

            WindowEvent::Resized(size) => {
                self.resize_surface(size.width, size.height);
            }

            WindowEvent::ScaleFactorChanged { .. } => {
                let size = self.window().inner_size();
                self.resize_surface(size.width, size.height);
            }

            WindowEvent::RedrawRequested => {
                let overlay_snapshot =
                    self.overlay_enabled.then(|| capture_snapshot(&self.stats, &self.firmware));

                // Get Pixels directly from the field (not via helper that gets the entire &mut self)
                let pixels = self.pixels.as_mut().expect("pixels not initialized");

                {
                    // Mutable borrow of the frame (lasts only within this block)
                    let frame = pixels.frame_mut();

                    // Immutable borrow of prometeu-core (different field, ok)
                    let src = self.hardware.gfx.front_buffer();

                    draw_rgb565_to_rgba8(src, frame);

                    if let Some(snapshot) = overlay_snapshot.as_ref() {
                        draw_overlay(frame, Hardware::W, Hardware::H, snapshot);
                    }
                } // <- frame borrow ends here

                if pixels.render().is_err() {
                    event_loop.exit();
                }
            }

            WindowEvent::KeyboardInput { event, .. } => {
                if let PhysicalKey::Code(code) = event.physical_key {
                    let is_down = event.state == ElementState::Pressed;

                    if is_down && code == KeyCode::KeyD && self.debugger.waiting_for_start {
                        self.debugger.waiting_for_start = false;
                        println!("[Debugger] Execution started!");
                    }

                    if is_down && code == KeyCode::F1 {
                        self.overlay_enabled = !self.overlay_enabled;
                    }
                }
            }

            _ => {}
        }
    }

    /// Called by `winit` when the application is idle and ready to perform updates.
    /// This is where the core execution loop lives.
    fn about_to_wait(&mut self, _event_loop: &ActiveEventLoop) {
        // 1. Process pending debug commands from the network.
        self.debugger.check_commands(&mut self.firmware, &mut self.hardware);

        // Sync inspection mode state.
        self.firmware.os.inspection_active = self.overlay_enabled || self.debugger.stream.is_some();

        // 2. Maintain filesystem connection if it was lost (e.g., directory removed).
        if let Some(root) = &self.fs_root {
            use prometeu_system::fs::FsState;
            if matches!(self.firmware.os.fs_state, FsState::Unmounted | FsState::Error(_))
                && std::path::Path::new(root).exists()
            {
                let backend = HostDirBackend::new(root);
                self.firmware.os.mount_fs(Box::new(backend));
            }
        }

        // 3. Timing Management (The heart of determinism).
        // We measure the elapsed time since the last iteration and add it to an
        // accumulator. We then execute exactly as many 60Hz slices as the
        // accumulator allows.
        let now = Instant::now();
        let mut frame_delta = now.duration_since(self.last_frame_time);

        // Safety cap: if the OS freezes or we fall behind too much, we don't try
        // to catch up indefinitely (avoiding the "death spiral").
        if frame_delta > Duration::from_millis(100) {
            frame_delta = Duration::from_millis(100);
        }

        self.last_frame_time = now;
        self.accumulator += frame_delta;

        // 🔥 Logic Update Loop: consumes time in exact 60Hz (16.66ms) slices.
        while self.accumulator >= self.frame_target_dt {
            // Unless the debugger is waiting for a 'start' command, advance the system.
            if !self.debugger.waiting_for_start {
                self.firmware.tick(&self.input.signals, &mut self.hardware);
                self.stats.record_host_cpu_time(self.firmware.os.last_frame_cpu_time_us);
            }

            // Sync pause state with audio.
            // We do this AFTER firmware.tick to avoid MasterPause/Resume commands
            // being cleared by the OS if a new logical frame starts in this tick.
            let is_paused = self.firmware.os.paused || self.debugger.waiting_for_start;
            if is_paused != self.last_paused_state {
                self.last_paused_state = is_paused;
                let cmd =
                    if is_paused { AudioCommand::MasterPause } else { AudioCommand::MasterResume };
                self.hardware.audio.commands.push(cmd);
            }

            // Sync virtual audio commands to the physical mixer.
            self.audio.send_commands(&mut self.hardware.audio.commands);

            self.accumulator -= self.frame_target_dt;
            self.stats.record_frame();
        }

        // 4. Feedback and Synchronization.
        self.audio.update_stats(&mut self.stats);

        // Update technical statistics displayed in the window title.
        self.stats.update(now, self.window, &self.hardware, &self.firmware);

        // Synchronize system logs to the host console.
        let last_seq = self.log_sink.last_seq().unwrap_or(u64::MAX);
        let new_events = if last_seq == u64::MAX {
            self.firmware.os.log_service.get_recent(4096)
        } else {
            self.firmware.os.log_service.get_after(last_seq)
        };
        self.log_sink.process_events(new_events);

        // 5. Request redraw so the host surface can present the latest machine frame
        // and, when enabled, compose the overlay in the host-only RGBA surface.
        self.request_redraw();
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use prometeu_firmware::BootTarget;
    use prometeu_hal::debugger_protocol::DEVTOOLS_PROTOCOL_VERSION;
    use std::io::{Read, Write};
    use std::net::TcpStream;

    #[test]
    #[ignore = "requires localhost TCP bind/connect; run via `cargo test -p prometeu-host-desktop-winit --lib -- --ignored`"]
    fn test_debug_port_opens() {
        let mut runner = HostRunner::new(None, None);
        let port = 9999;
        runner.set_boot_target(BootTarget::Cartridge {
            path: "dummy.bin".to_string(),
            debug: true,
            debug_port: port,
        });

        assert!(runner.debugger.waiting_for_start);
        assert!(runner.debugger.listener.is_some());

        // Check if we can connect
        {
            let mut stream =
                TcpStream::connect(format!("127.0.0.1:{}", port)).expect("Should connect");
            // Short sleep to ensure the OS processes
            std::thread::sleep(std::time::Duration::from_millis(100));

            // Simulates the loop to accept the connection
            runner.debugger.check_commands(&mut runner.firmware, &mut runner.hardware);
            assert!(runner.debugger.stream.is_some(), "Stream should have been kept open");

            // Handshake Check
            let mut buf = [0u8; 2048];
            let n = stream.read(&mut buf).expect("Should read handshake");
            let resp: serde_json::Value =
                serde_json::from_slice(&buf[..n]).expect("Handshake should be valid JSON");
            assert_eq!(resp["type"], "handshake");
            assert_eq!(resp["protocol_version"], DEVTOOLS_PROTOCOL_VERSION);

            // Send start via JSON
            stream
                .write_all(b"{\"type\":\"start\"}\n")
                .expect("Connection should be open for writing");
            std::thread::sleep(std::time::Duration::from_millis(50));

            // Process the received command
            runner.debugger.check_commands(&mut runner.firmware, &mut runner.hardware);
            assert!(
                !runner.debugger.waiting_for_start,
                "Execution should have started after start command"
            );
            assert!(
                runner.debugger.listener.is_some(),
                "Listener should remain open for reconnections"
            );
        }

        // Now that the stream is out of the test scope, the runner should detect closure on next check
        std::thread::sleep(std::time::Duration::from_millis(50));
        runner.debugger.check_commands(&mut runner.firmware, &mut runner.hardware);
        assert!(
            runner.debugger.stream.is_none(),
            "Stream should have been closed after client disconnected"
        );
    }

    #[test]
    #[ignore = "requires localhost TCP bind/connect; run via `cargo test -p prometeu-host-desktop-winit --lib -- --ignored`"]
    fn test_debug_reconnection() {
        let mut runner = HostRunner::new(None, None);
        let port = 9998;
        runner.set_boot_target(BootTarget::Cartridge {
            path: "dummy.bin".to_string(),
            debug: true,
            debug_port: port,
        });

        // 1. Connect and start
        {
            let mut stream =
                TcpStream::connect(format!("127.0.0.1:{}", port)).expect("Should connect 1");
            std::thread::sleep(std::time::Duration::from_millis(50));
            runner.debugger.check_commands(&mut runner.firmware, &mut runner.hardware);
            assert!(runner.debugger.stream.is_some());

            stream.write_all(b"{\"type\":\"start\"}\n").expect("Should write start");
            std::thread::sleep(std::time::Duration::from_millis(50));
            runner.debugger.check_commands(&mut runner.firmware, &mut runner.hardware);
            assert!(!runner.debugger.waiting_for_start);
            // Currently the listener is closed here.
        }

        // 2. Disconnect (clears stream in runner)
        std::thread::sleep(std::time::Duration::from_millis(50));
        runner.debugger.check_commands(&mut runner.firmware, &mut runner.hardware);
        assert!(runner.debugger.stream.is_none());

        // 3. Try to reconnect - SHOULD FAIL currently, but we want it to WORK
        let stream2 = TcpStream::connect(format!("127.0.0.1:{}", port));
        assert!(stream2.is_ok(), "Should accept new connection even after start");

        std::thread::sleep(std::time::Duration::from_millis(50));
        runner.debugger.check_commands(&mut runner.firmware, &mut runner.hardware);
        assert!(
            runner.debugger.stream.is_some(),
            "Stream should have been accepted on reconnection"
        );
    }

    #[test]
    #[ignore = "requires localhost TCP bind/connect; run via `cargo test -p prometeu-host-desktop-winit --lib -- --ignored`"]
    fn test_debug_refuse_second_connection() {
        let mut runner = HostRunner::new(None, None);
        let port = 9997;
        runner.set_boot_target(BootTarget::Cartridge {
            path: "dummy.bin".to_string(),
            debug: true,
            debug_port: port,
        });

        // 1. First connection
        let mut _stream1 =
            TcpStream::connect(format!("127.0.0.1:{}", port)).expect("Should connect 1");
        std::thread::sleep(std::time::Duration::from_millis(50));
        runner.debugger.check_commands(&mut runner.firmware, &mut runner.hardware);
        assert!(runner.debugger.stream.is_some());

        // 2. Second connection
        let mut stream2 = TcpStream::connect(format!("127.0.0.1:{}", port))
            .expect("Should connect 2 (OS accepts)");
        std::thread::sleep(std::time::Duration::from_millis(50));
        runner.debugger.check_commands(&mut runner.firmware, &mut runner.hardware); // Should accept and close stream2

        // Check if stream2 was closed by the server
        let mut buf = [0u8; 10];
        stream2.set_read_timeout(Some(std::time::Duration::from_millis(100))).unwrap();
        let res = stream2.read(&mut buf);
        assert!(
            matches!(res, Ok(0)) || res.is_err(),
            "Second connection should be closed by server"
        );

        assert!(runner.debugger.stream.is_some(), "First connection should continue active");
    }

    #[test]
    #[ignore = "requires localhost TCP bind/connect; run via `cargo test -p prometeu-host-desktop-winit --lib -- --ignored`"]
    fn test_get_state_returns_response() {
        let mut runner = HostRunner::new(None, None);
        let port = 9996;
        runner.set_boot_target(BootTarget::Cartridge {
            path: "dummy.bin".to_string(),
            debug: true,
            debug_port: port,
        });

        let stream = TcpStream::connect(format!("127.0.0.1:{}", port)).expect("Should connect");
        std::thread::sleep(std::time::Duration::from_millis(100));
        runner.debugger.check_commands(&mut runner.firmware, &mut runner.hardware);

        use std::io::BufRead;
        let mut reader = std::io::BufReader::new(stream);

        let mut line = String::new();
        reader.read_line(&mut line).expect("Should read handshake");
        assert!(line.contains("handshake"));

        // Send getState
        reader.get_mut().write_all(b"{\"type\":\"getState\"}\n").expect("Should write getState");
        std::thread::sleep(std::time::Duration::from_millis(100));

        runner.debugger.check_commands(&mut runner.firmware, &mut runner.hardware);

        // Check if response received (may have events/logs before)
        loop {
            line.clear();
            reader.read_line(&mut line).expect("Should read line");
            if line.is_empty() {
                break;
            }

            if let Ok(resp) = serde_json::from_str::<serde_json::Value>(&line) {
                if resp["type"] == "getState" {
                    return;
                }
            }
        }
        panic!("Did not receive getState response");
    }

    #[test]
    #[ignore = "requires localhost TCP bind/connect; run via `cargo test -p prometeu-host-desktop-winit --lib -- --ignored`"]
    fn test_debug_resume_on_disconnect() {
        let mut runner = HostRunner::new(None, None);
        let port = 9995;
        runner.set_boot_target(BootTarget::Cartridge {
            path: "dummy.bin".to_string(),
            debug: true,
            debug_port: port,
        });

        // 1. Connect and pause
        {
            let mut stream =
                TcpStream::connect(format!("127.0.0.1:{}", port)).expect("Should connect");
            std::thread::sleep(std::time::Duration::from_millis(50));
            runner.debugger.check_commands(&mut runner.firmware, &mut runner.hardware);

            stream.write_all(b"{\"type\":\"pause\"}\n").expect("Should write pause");
            std::thread::sleep(std::time::Duration::from_millis(50));
            runner.debugger.check_commands(&mut runner.firmware, &mut runner.hardware);
            assert!(runner.firmware.os.paused, "VM should be paused");
        }

        // 2. Disconnect (stream goes out of scope)
        std::thread::sleep(std::time::Duration::from_millis(50));
        runner.debugger.check_commands(&mut runner.firmware, &mut runner.hardware);

        // 3. Check if unpaused
        assert!(!runner.firmware.os.paused, "VM should have unpaused after disconnect");
        assert!(!runner.debugger.waiting_for_start, "VM should have left waiting_for_start state");
    }
}