#![deny(clippy::all)]
#![forbid(unsafe_code)]

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

const WIDTH: u32 = 320;
const HEIGHT: u32 = 240;
const BOX_SIZE: i16 = 64;

/// Representation of the application state. In this example, a box will bounce around the screen.
struct World {
    box_x: i16,
    box_y: i16,
    velocity_x: i16,
    velocity_y: i16,
}

fn main() -> Result<(), Error> {
    let event_loop = EventLoop::new();
    let mut input = WinitInputHelper::new();
    let window = {
        let size = LogicalSize::new(WIDTH as f64, HEIGHT as f64);
        WindowBuilder::new()
            .with_title("Hello Pixels")
            .with_inner_size(size)
            .with_min_inner_size(size)
            .build(&event_loop)
            .unwrap()
    };
    let mut hidpi_factor = window.hidpi_factor();

    let mut pixels = {
        let surface = Surface::create(&window);
        let surface_texture = SurfaceTexture::new(WIDTH, HEIGHT, surface);
        Pixels::new(WIDTH, HEIGHT, surface_texture)?
    };
    let mut world = World::new();

    event_loop.run(move |event, _, control_flow| {
        // Draw the current frame
        if let Event::WindowEvent {
            event: WindowEvent::RedrawRequested,
            ..
        } = event
        {
            world.draw(pixels.get_frame());
            pixels.render();
        }

        // Handle input events
        if input.update(event) {
            // Close events
            if input.key_pressed(VirtualKeyCode::Escape) || input.quit() {
                *control_flow = ControlFlow::Exit;
                return;
            }

            // Adjust high DPI factor
            if let Some(factor) = input.hidpi_changed() {
                hidpi_factor = factor;
            }

            // Resize the window
            if let Some(size) = input.window_resized() {
                let size = size.to_physical(hidpi_factor);
                let width = size.width.round() as u32;
                let height = size.height.round() as u32;

                pixels.resize(width, height);
            }

            // Update internal state and request a redraw
            world.update();
            window.request_redraw();
        }
    });
}

impl World {
    /// Create a new `World` instance that can draw a moving box.
    fn new() -> Self {
        Self {
            box_x: 24,
            box_y: 16,
            velocity_x: 1,
            velocity_y: 1,
        }
    }

    /// Update the `World` internal state; bounce the box around the screen.
    fn update(&mut self) {
        if self.box_x < 0 || self.box_x + BOX_SIZE >= WIDTH as i16 {
            self.velocity_x *= -1;
        }
        if self.box_y < 0 || self.box_y + BOX_SIZE >= HEIGHT as i16 {
            self.velocity_y *= -1;
        }

        self.box_x += self.velocity_x;
        self.box_y += self.velocity_y;
    }

    /// Draw the `World` state to the frame buffer.
    ///
    /// Assumes the default texture format: [`wgpu::TextureFormat::Rgba8UnormSrgb`]
    fn draw(&self, frame: &mut [u8]) {
        for (i, pixel) in frame.chunks_exact_mut(4).enumerate() {
            let x = (i % WIDTH as usize) as i16;
            let y = (i / WIDTH as usize) as i16;

            let inside_the_box = x >= self.box_x
                && x < self.box_x + BOX_SIZE
                && y >= self.box_y
                && y < self.box_y + BOX_SIZE;

            let rgba = if inside_the_box {
                [0x5e, 0x48, 0xe8, 0xff]
            } else {
                [0x48, 0xb2, 0xe8, 0xff]
            };

            pixel.copy_from_slice(&rgba);
        }
    }
}