// I used: http://devernay.free.fr/hacks/chip8/C8TECH10.HTM#00E0
// and https://en.wikipedia.org/wiki/CHIP-8#Opcode_table
// for information about how to implement a CHIP-8 Emulator
use chip8::emu::Chip8;
use std::path::Path;

use pixels::{wgpu::Surface, Pixels, SurfaceTexture};
use winit::dpi::LogicalSize;
use winit::event::{Event, VirtualKeyCode};
use winit::event_loop::{ControlFlow, EventLoop};
use winit::window::{Window, WindowBuilder};
use winit_input_helper::WinitInputHelper;

static WIDTH: u32 = 64;
static HEIGHT: u32 = 32;

fn main() {
    let mut chip8: Chip8 = Default::default();
    let mut input = WinitInputHelper::new();
    let event_loop = EventLoop::new();
    let window = init_window(&event_loop);
    let mut pixels = init_pixels(&window);

    let rom_path = Path::new("./games/c8games/INVADERS");
    chip8.load_rom(rom_path).expect("Unable to load ROM");

    event_loop.run(move |event, _, control_flow| {
        if let Event::RedrawRequested(_) = event {
            draw(&chip8.display.buf, pixels.get_frame());
            if pixels
                .render()
                .map_err(|e| eprintln!("pixels.render()  failed: {}", e))
                .is_err()
            {
                *control_flow = ControlFlow::Exit;
                return;
            }
        }

        if input.update(&event) {
            handle_input(&mut chip8, &mut input, control_flow);

            if let Some(size) = input.window_resized() {
                pixels.resize(size.width, size.height);
            }

            chip8.execute_cycle();
            if chip8.request_redraw {
                window.request_redraw();
            }
        }
    });
}

fn handle_input(chip8: &mut Chip8, input: &mut WinitInputHelper, control_flow: &mut ControlFlow) {
    if input.key_pressed(VirtualKeyCode::Escape) || input.quit() {
        *control_flow = ControlFlow::Exit;
        return;
    }

    // 1 -> 1
    if input.key_pressed(VirtualKeyCode::Key1) {
        chip8.key.set_key(0x1);
    }
    if input.key_released(VirtualKeyCode::Key1) {
        chip8.key.unset_key(0x1);
    }
    // 2 -> 2
    if input.key_pressed(VirtualKeyCode::Key2) {
        chip8.key.set_key(0x2);
    }
    if input.key_released(VirtualKeyCode::Key2) {
        chip8.key.unset_key(0x2);
    }
    // 3 -> 3
    if input.key_pressed(VirtualKeyCode::Key3) {
        chip8.key.set_key(0x3);
    }
    if input.key_released(VirtualKeyCode::Key3) {
        chip8.key.unset_key(0x3);
    }
    // 4 -> C
    if input.key_pressed(VirtualKeyCode::Key4) {
        chip8.key.set_key(0xC);
    }
    if input.key_released(VirtualKeyCode::Key4) {
        chip8.key.unset_key(0xC);
    }
    // Q -> 4
    if input.key_pressed(VirtualKeyCode::Q) {
        chip8.key.set_key(0x4);
    }
    if input.key_released(VirtualKeyCode::Q) {
        chip8.key.unset_key(0x4);
    }
    // W -> 5
    if input.key_pressed(VirtualKeyCode::W) {
        chip8.key.set_key(0x5);
    }
    if input.key_released(VirtualKeyCode::W) {
        chip8.key.unset_key(0x5);
    }
    // E -> 6
    if input.key_pressed(VirtualKeyCode::E) {
        chip8.key.set_key(0x6);
    }
    if input.key_released(VirtualKeyCode::E) {
        chip8.key.unset_key(0x6);
    }
    // R -> D
    if input.key_pressed(VirtualKeyCode::R) {
        chip8.key.set_key(0xD);
    }
    if input.key_released(VirtualKeyCode::R) {
        chip8.key.unset_key(0xD);
    }
    // A -> 7
    if input.key_pressed(VirtualKeyCode::A) {
        chip8.key.set_key(0x7);
    }
    if input.key_released(VirtualKeyCode::A) {
        chip8.key.unset_key(0x7);
    }
    // S -> 8
    if input.key_pressed(VirtualKeyCode::S) {
        chip8.key.set_key(0x8);
    }
    if input.key_released(VirtualKeyCode::S) {
        chip8.key.unset_key(0x8);
    }
    // D -> 9
    if input.key_pressed(VirtualKeyCode::D) {
        chip8.key.set_key(0x9);
    }
    if input.key_released(VirtualKeyCode::D) {
        chip8.key.unset_key(0x9);
    }
    // F -> A
    if input.key_pressed(VirtualKeyCode::F) {
        chip8.key.set_key(0xE);
    }
    if input.key_released(VirtualKeyCode::F) {
        chip8.key.unset_key(0xE);
    }
    // Z -> A
    if input.key_pressed(VirtualKeyCode::Z) {
        chip8.key.set_key(0xA);
    }
    if input.key_released(VirtualKeyCode::Z) {
        chip8.key.unset_key(0xA);
    }
    // X -> 0
    if input.key_pressed(VirtualKeyCode::X) {
        chip8.key.set_key(0x0);
    }
    if input.key_released(VirtualKeyCode::X) {
        chip8.key.unset_key(0x0);
    }
    // C -> B
    if input.key_pressed(VirtualKeyCode::C) {
        chip8.key.set_key(0xB);
    }
    if input.key_released(VirtualKeyCode::C) {
        chip8.key.unset_key(0xB);
    }
    // V -> F
    if input.key_pressed(VirtualKeyCode::V) {
        chip8.key.set_key(0xF);
    }
    if input.key_released(VirtualKeyCode::V) {
        chip8.key.unset_key(0xF);
    }
}

fn init_pixels(window: &Window) -> Pixels {
    let surface = Surface::create(window);
    let texture = SurfaceTexture::new(WIDTH, HEIGHT, surface);
    Pixels::new(WIDTH, HEIGHT, texture).unwrap()
}

fn init_window(event_loop: &EventLoop<()>) -> Window {
    const SCALE: u32 = 10;
    let min_size = LogicalSize::new(WIDTH as f64, HEIGHT as f64);
    let size = LogicalSize::new((WIDTH * SCALE) as f64, (HEIGHT * SCALE) as f64);
    WindowBuilder::new()
        .with_title("Chip8 Emulator")
        .with_inner_size(size)
        .with_min_inner_size(min_size)
        .build(event_loop)
        .unwrap()
}

fn draw(chip8_gfx: &[u8], frame: &mut [u8]) {
    for (i, pixel) in frame.chunks_exact_mut(4).enumerate() {
        let rgba = if chip8_gfx[i] == 1 {
            [0xFF; 4]
        } else {
            [0x00; 4]
        };

        pixel.copy_from_slice(&rgba);
    }
}