// 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/ibm_logo.ch8");
    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) {
            if input.key_pressed(VirtualKeyCode::Escape) || input.quit() {
                *control_flow = ControlFlow::Exit;
                return;
            }

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

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

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);
    }
}