use std::time::{Duration, Instant};

use pixels::{Pixels, SurfaceTexture};
use prometeu_core::peripherals::InputSignals;
use prometeu_core::Machine;
use winit::{
    application::ApplicationHandler,
    dpi::LogicalSize,
    event::{ElementState, MouseButton, WindowEvent},
    event_loop::{ActiveEventLoop, ControlFlow, EventLoop},
    keyboard::{KeyCode, PhysicalKey},
    window::{Window, WindowAttributes, WindowId},
};

fn main() -> Result<(), Box<dyn std::error::Error>> {
    let event_loop = EventLoop::new()?;

    let mut app = PrometeuApp::new();
    event_loop.run_app(&mut app)?;

    Ok(())
}

struct PrometeuApp {
    window: Option<&'static Window>,
    pixels: Option<Pixels<'static>>,
    
    machine: Machine,

    input_signals: InputSignals,
    
    frame_target_dt: Duration,
    last_frame_time: Instant,
    accumulator: Duration,

    last_stats_update: Instant,
    frames_since_last_update: u64,
}

impl PrometeuApp {
    fn new() -> Self {
        let target_fps = 60;

        Self {
            window: None,
            pixels: None,
            
            machine: Machine::new(),

            input_signals: InputSignals::default(),
            
            frame_target_dt: Duration::from_nanos(1_000_000_000 / target_fps),
            last_frame_time: Instant::now(),
            accumulator: Duration::ZERO,

            last_stats_update: Instant::now(),
            frames_since_last_update: 0,
        }
    }

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

    // fn pixels_mut(&mut self) -> &mut Pixels<'static> {
    //     self.pixels.as_mut().expect("pixels 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 PrometeuApp {
    fn resumed(&mut self, event_loop: &ActiveEventLoop) {
        let attrs = WindowAttributes::default()
            .with_title(format!("PROMETEU | GFX: {:.1} KB | FPS: {:.1} | Frame: {}", 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 vira &'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 = Pixels::new(Machine::W as u32, Machine::H as u32, surface_texture)
            .expect("failed to create Pixels");

        pixels.frame_mut().fill(0);

        self.pixels = Some(pixels);

        event_loop.set_control_flow(ControlFlow::Poll);
    }


    fn window_event(&mut self, event_loop: &ActiveEventLoop, _id: WindowId, event: WindowEvent) {
        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 => {
                // Pegue o Pixels diretamente do campo (não via helper que pega &mut self inteiro)
                let pixels = self.pixels.as_mut().expect("pixels not initialized");

                {
                    // Borrow mutável do frame (dura só dentro deste bloco)
                    let frame = pixels.frame_mut();

                    // Borrow imutável do core (campo diferente, ok)
                    let src = self.machine.gfx.front_buffer();

                    draw_rgb565_to_rgba8(src, frame);
                } // <- frame borrow termina aqui

                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;
                    match code {
                        KeyCode::ArrowUp => self.input_signals.up_signal = is_down,
                        KeyCode::ArrowDown => self.input_signals.down_signal = is_down,
                        KeyCode::ArrowLeft => self.input_signals.left_signal = is_down,
                        KeyCode::ArrowRight => self.input_signals.right_signal = is_down,

                        // A/B (troque depois como quiser)
                        KeyCode::KeyA => self.input_signals.a_signal = is_down,
                        KeyCode::KeyD => self.input_signals.d_signal = is_down,
                        KeyCode::KeyW => self.input_signals.w_signal = is_down,
                        KeyCode::KeyS => self.input_signals.s_signal = is_down,
                        KeyCode::KeyQ => self.input_signals.q_signal = is_down,
                        KeyCode::KeyE => self.input_signals.e_signal = is_down,

                        KeyCode::KeyZ => self.input_signals.start_signal = is_down,
                        KeyCode::ShiftLeft | KeyCode::ShiftRight => self.input_signals.select_signal = is_down,

                        _ => {}
                    }
                }
            }

            WindowEvent::CursorMoved { position, .. } => {
                let v = window_to_fb(position.x as f32, position.y as f32, self.window());
                self.input_signals.x_pos = v.0;
                self.input_signals.y_pos = v.1;
            }

            WindowEvent::MouseInput { state, button, .. } => {
                if button == MouseButton::Left {
                    match state {
                        ElementState::Pressed => {
                            self.input_signals.t_signal = true;
                        }
                        ElementState::Released => {
                            self.input_signals.t_signal = false;
                        }
                    }
                }
            }

            _ => {}
        }
    }

    fn about_to_wait(&mut self, _event_loop: &ActiveEventLoop) {
        let now = Instant::now();
        let mut frame_delta = now.duration_since(self.last_frame_time);

        // Limitador para evitar a "espiral da morte" se o SO travar (máximo de 100ms por volta)
        if frame_delta > Duration::from_millis(100) {
            frame_delta = Duration::from_millis(100);
        }

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

        // 🔥 O coração do determinismo: consome o tempo em fatias exatas de 60Hz
        while self.accumulator >= self.frame_target_dt {
            self.machine.step_frame(&self.input_signals);
            self.accumulator -= self.frame_target_dt;
            self.frames_since_last_update += 1;
        }

        // Atualiza estatísticas a cada 1 segundo real
        let stats_elapsed = now.duration_since(self.last_stats_update);
        if stats_elapsed >= Duration::from_secs(1) {
            if let Some(window) = self.window {
                let fps = self.frames_since_last_update as f64 / stats_elapsed.as_secs_f64();
                let kb = self.machine.gfx.memory_usage_bytes() as f64 / 1024.0;

                let frame_budget_us = 16666.0;
                let cpu_load = (self.machine.last_frame_cpu_time_us as f64 / frame_budget_us) * 100.0;

                let title = format!(
                    "PROMETEU | GFX: {:.1} KB | FPS: {:.1} | Load: {:.1}% | Frame: {}",
                    kb, fps, cpu_load, self.machine.frame_index
                );
                window.set_title(&title);
            }

            self.last_stats_update = now;
            self.frames_since_last_update = 0;
        }

        self.request_redraw();
    }
}

/// Mapeamento simples: window coords -> framebuffer coords (stretch).
/// Depois podemos fazer letterbox/aspect-ratio correto.
fn window_to_fb(wx: f32, wy: f32, window: &Window) -> (i32, i32) {
    let size = window.inner_size();
    let fb_w = Machine::W as f32;
    let fb_h = Machine::H as f32;

    let x = (wx * fb_w / size.width as f32).floor() as i32;
    let y = (wy * fb_h / size.height as f32).floor() as i32;

    (x.clamp(0, Machine::W as i32 - 1), y.clamp(0, Machine::H as i32 - 1))
}

/// Copia RGB565 (u16) -> RGBA8888 (u8[4]) para o frame do pixels.
/// Formato do pixels: RGBA8.
fn draw_rgb565_to_rgba8(src: &[u16], dst_rgba: &mut [u8]) {
    for (i, &px) in src.iter().enumerate() {
        let (r8, g8, b8) = rgb565_to_rgb888(px);
        let o = i * 4;
        dst_rgba[o] = r8;
        dst_rgba[o + 1] = g8;
        dst_rgba[o + 2] = b8;
        dst_rgba[o + 3] = 0xFF;
    }
}

/// Expande RGB565 para RGB888 (replicação de bits altos).
#[inline(always)]
fn rgb565_to_rgb888(px: u16) -> (u8, u8, u8) {
    let r5 = ((px >> 11) & 0x1F) as u8;
    let g6 = ((px >> 5) & 0x3F) as u8;
    let b5 = (px & 0x1F) as u8;

    let r8 = (r5 << 3) | (r5 >> 2);
    let g8 = (g6 << 2) | (g6 >> 4);
    let b8 = (b5 << 3) | (b5 >> 2);

    (r8, g8, b8)
}