use std::iter;

use winit::{
    event::*,
    event_loop::EventLoop,
    keyboard::{KeyCode, PhysicalKey},
    window::{Window, WindowBuilder},
};

struct State<'a> {
    #[allow(dead_code)]
    instance: wgpu::Instance,
    #[allow(dead_code)]
    adapter: wgpu::Adapter,
    surface: wgpu::Surface<'a>,
    device: wgpu::Device,
    queue: wgpu::Queue,
    config: wgpu::SurfaceConfiguration,
    size: winit::dpi::PhysicalSize<u32>,
    clear_color: wgpu::Color,
    window: &'a Window,
}

impl<'a> State<'a> {
    async fn new(window: &'a Window) -> State<'a> {
        let size = window.inner_size();

        // The instance is a handle to our GPU
        // BackendBit::PRIMARY => Vulkan + Metal + DX12 + Browser WebGPU
        let instance = wgpu::Instance::new(wgpu::InstanceDescriptor {
            backends: wgpu::Backends::PRIMARY,
            ..Default::default()
        });

        // # Safety
        //
        // The surface needs to live as long as the window that created it.
        // State owns the window so this should be safe.
        let surface = instance.create_surface(window).unwrap();

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

        let (device, queue) = adapter
            .request_device(
                &wgpu::DeviceDescriptor {
                    label: None,
                    required_features: wgpu::Features::empty(),
                    // WebGL doesn't support all of wgpu's features, so if
                    // we're building for the web we'll have to disable some.
                    required_limits: if cfg!(target_arch = "wasm32") {
                        wgpu::Limits::downlevel_webgl2_defaults()
                    } else {
                        wgpu::Limits::default()
                    },
                },
                None, // Trace path
            )
            .await
            .unwrap();

        let surface_caps = surface.get_capabilities(&adapter);
        // Shader code in this tutorial assumes an Srgb surface texture. Using a different
        // one will result all the colors comming out darker. If you want to support non
        // Srgb surfaces, you'll need to account for that when drawing to the frame.
        let surface_format = surface_caps
            .formats
            .iter()
            .copied()
            .find(|f| f.is_srgb())
            .unwrap_or(surface_caps.formats[0]);
        let config = wgpu::SurfaceConfiguration {
            usage: wgpu::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],
            desired_maximum_frame_latency: 2,
            view_formats: vec![],
        };

        let clear_color = wgpu::Color::BLACK;

        Self {
            instance,
            adapter,
            surface,
            device,
            queue,
            config,
            clear_color,
            size,
            window,
        }
    }

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

    pub fn resize(&mut self, new_size: winit::dpi::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 input(&mut self, event: &WindowEvent) -> bool {
        match event {
            WindowEvent::CursorMoved { position, .. } => {
                self.clear_color = wgpu::Color {
                    r: position.x as f64 / self.size.width as f64,
                    g: position.y as f64 / self.size.height as f64,
                    b: 1.0,
                    a: 1.0,
                };
                true
            }
            _ => false,
        }
    }

    fn update(&mut self) {}

    fn render(&mut self) -> Result<(), wgpu::SurfaceError> {
        let output = self.surface.get_current_texture()?;
        let view = output
            .texture
            .create_view(&wgpu::TextureViewDescriptor::default());

        let mut encoder = self
            .device
            .create_command_encoder(&wgpu::CommandEncoderDescriptor {
                label: Some("Render Encoder"),
            });

        {
            let _render_pass = encoder.begin_render_pass(&wgpu::RenderPassDescriptor {
                label: Some("Render Pass"),
                color_attachments: &[Some(wgpu::RenderPassColorAttachment {
                    view: &view,
                    resolve_target: None,
                    ops: wgpu::Operations {
                        load: wgpu::LoadOp::Clear(self.clear_color),
                        store: wgpu::StoreOp::Store,
                    },
                })],
                depth_stencil_attachment: None,
                occlusion_query_set: None,
                timestamp_writes: None,
            });
        }

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

        Ok(())
    }
}

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

async fn run() {
    env_logger::init();
    let event_loop = EventLoop::new().unwrap();
    let window = WindowBuilder::new().build(&event_loop).unwrap();

    // State::new uses async code, so we're going to wait for it to finish
    let mut state = State::new(&window).await;

    event_loop
        .run(move |event, control_flow| {
            match event {
                Event::WindowEvent {
                    ref event,
                    window_id,
                } if window_id == state.window().id() => {
                    if !state.input(event) {
                        match event {
                            WindowEvent::CloseRequested
                            | WindowEvent::KeyboardInput {
                                event:
                                    KeyEvent {
                                        state: ElementState::Pressed,
                                        physical_key: PhysicalKey::Code(KeyCode::Escape),
                                        ..
                                    },
                                ..
                            } => control_flow.exit(),
                            WindowEvent::Resized(physical_size) => {
                                state.resize(*physical_size);
                            }
                            WindowEvent::RedrawRequested => {
                                state.window().request_redraw();
                                state.update();
                                match state.render() {
                                    Ok(_) => {}
                                    // Reconfigure the surface if it's lost or outdated
                                    Err(
                                        wgpu::SurfaceError::Lost | wgpu::SurfaceError::Outdated,
                                    ) => state.resize(state.size),
                                    // The system is out of memory, we should probably quit
                                    Err(wgpu::SurfaceError::OutOfMemory) => {
                                        log::error!("OutOfMemory");
                                        control_flow.exit();
                                    }
                                    // We're ignoring timeouts
                                    Err(wgpu::SurfaceError::Timeout) => {
                                        log::warn!("Surface timeout")
                                    }
                                }
                            }
                            _ => {}
                        }
                    }
                }
                _ => {}
            }
        })
        .unwrap();
}