#![cfg_attr(windows, windows_subsystem = "windows")]

use std::iter::once;

use wgpu::{
    Backends, Color, CommandEncoderDescriptor, Device, DeviceDescriptor, Features, Instance,
    InstanceDescriptor, Limits, LoadOp, Operations, PowerPreference, Queue,
    RenderPassColorAttachment, RenderPassDescriptor, RequestAdapterOptions, Surface,
    SurfaceConfiguration, SurfaceError, TextureUsages, TextureViewDescriptor,
};
use winit::{
    dpi::PhysicalSize,
    event::{ElementState, Event, KeyboardInput, VirtualKeyCode, WindowEvent},
    event_loop::{ControlFlow, EventLoop},
    window::{Window, WindowBuilder},
};
use winit_fullscreen::*;

fn main() {
    pollster::block_on(run());
}

async fn run() {
    let event_loop = EventLoop::new();
    let window = WindowBuilder::new()
        .with_title("winit-fullscreen example")
        .with_inner_size(PhysicalSize::new(800, 600))
        .build(&event_loop)
        .unwrap();

    let mut state = State::new(window).await;

    event_loop.run(move |event, _target, control_flow| {
        *control_flow = ControlFlow::Poll;

        match event {
            Event::WindowEvent {
                event, window_id, ..
            } if window_id == state.window().id() => match event {
                WindowEvent::CloseRequested => *control_flow = ControlFlow::Exit,
                WindowEvent::KeyboardInput { input, .. } => match input {
                    KeyboardInput {
                        state: ElementState::Pressed,
                        virtual_keycode: Some(VirtualKeyCode::Escape),
                        ..
                    } => *control_flow = ControlFlow::Exit,
                    KeyboardInput {
                        state: ElementState::Pressed,
                        virtual_keycode: Some(VirtualKeyCode::Return),
                        ..
                    } => {
                        // Toggle fullscreen
                        state.window().toggle_fullscreen();
                    }
                    _ => {}
                },
                WindowEvent::Resized(physical_size) => state.resize(physical_size),
                WindowEvent::ScaleFactorChanged { new_inner_size, .. } => {
                    state.resize(*new_inner_size)
                }
                _ => {}
            },
            Event::RedrawRequested(window_id) if window_id == state.window().id() => {
                match state.render() {
                    Ok(_) => {}
                    Err(SurfaceError::Lost) => state.resize(state.size),
                    Err(SurfaceError::OutOfMemory) => *control_flow = ControlFlow::Exit,
                    Err(e) => eprintln!("{:?}", e),
                }
            }
            Event::MainEventsCleared => {
                state.window().request_redraw();
            }
            _ => {}
        }
    })
}

struct State {
    surface: Surface,
    device: Device,
    queue: Queue,
    config: SurfaceConfiguration,
    size: PhysicalSize<u32>,
    window: Window,
}

impl State {
    async fn new(window: Window) -> Self {
        let size = window.inner_size();

        let instance = Instance::new(InstanceDescriptor {
            backends: Backends::all(),
            dx12_shader_compiler: Default::default(),
        });

        let surface = unsafe { instance.create_surface(&window) }.unwrap();

        let adapter = instance
            .request_adapter(&RequestAdapterOptions {
                power_preference: PowerPreference::default(),
                compatible_surface: Some(&surface),
                force_fallback_adapter: false,
            })
            .await
            .unwrap();

        let (device, queue) = adapter
            .request_device(
                &DeviceDescriptor {
                    features: Features::empty(),
                    limits: Limits::default(),
                    label: None,
                },
                None,
            )
            .await
            .unwrap();

        let surface_caps = surface.get_capabilities(&adapter);
        let surface_format = surface_caps
            .formats
            .iter()
            .copied()
            .find(|f| f.describe().srgb)
            .unwrap_or(surface_caps.formats[0]);

        let config = SurfaceConfiguration {
            usage: TextureUsages::RENDER_ATTACHMENT,
            format: surface_format,
            width: size.width,
            height: size.height,
            present_mode: surface_caps.present_modes[0],
            alpha_mode: surface_caps.alpha_modes[0],
            view_formats: vec![],
        };
        surface.configure(&device, &config);

        Self {
            window,
            surface,
            device,
            queue,
            config,
            size,
        }
    }

    pub fn window(&self) -> &Window {
        &self.window
    }

    fn resize(&mut self, new_size: PhysicalSize<u32>) {
        if new_size.width > 0 && new_size.height > 0 {
            self.size = new_size;
            self.config.width = new_size.width;
            self.config.height = new_size.height;
            self.surface.configure(&self.device, &self.config);
        }
    }

    fn render(&mut self) -> Result<(), SurfaceError> {
        let output = self.surface.get_current_texture()?;
        let view = output
            .texture
            .create_view(&TextureViewDescriptor::default());
        let mut encoder = self
            .device
            .create_command_encoder(&CommandEncoderDescriptor {
                label: Some("Render Encoder"),
            });

        {
            let _render_pass = encoder.begin_render_pass(&RenderPassDescriptor {
                label: Some("Render Pass"),
                color_attachments: &[Some(RenderPassColorAttachment {
                    view: &view,
                    resolve_target: None,
                    ops: Operations {
                        load: LoadOp::Clear(Color {
                            r: 0.1,
                            g: 0.2,
                            b: 0.3,
                            a: 1.0,
                        }),
                        store: true,
                    },
                })],
                depth_stencil_attachment: None,
            });
        }

        self.queue.submit(once(encoder.finish()));
        output.present();

        Ok(())
    }
}