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

use winit::window::Window;

use wgpu::util::DeviceExt;

#[repr(C)]
#[derive(Copy, Clone, Debug, bytemuck::Pod, bytemuck::Zeroable)]
struct Vertex {
    position: [f32; 3],
    color: [f32; 3],
}

impl Vertex {
    fn desc() -> wgpu::VertexBufferLayout<'static> {
        wgpu::VertexBufferLayout {
            array_stride: std::mem::size_of::<Vertex>() as wgpu::BufferAddress,
            step_mode: wgpu::VertexStepMode::Vertex,
            attributes: &[
                wgpu::VertexAttribute {
                    offset: 0,
                    shader_location: 0,
                    format: wgpu::VertexFormat::Float32x3,
                },
                wgpu::VertexAttribute {
                    offset: std::mem::size_of::<[f32; 3]>() as wgpu::BufferAddress,
                    shader_location: 1,
                    format: wgpu::VertexFormat::Float32x3,
                }
            ]
        }
    }
}

const VERTICES: &[Vertex] = &[
    Vertex { position: [-0.0868241, 0.49240386, 0.0], color: [0.5, 0.0, 0.5] }, // A
    Vertex { position: [-0.49513406, 0.06958647, 0.0], color: [0.5, 0.0, 0.5] }, // B
    Vertex { position: [-0.21918549, -0.44939706, 0.0], color: [0.5, 0.0, 0.5] }, // C
    Vertex { position: [0.35966998, -0.3473291, 0.0], color: [0.5, 0.0, 0.5] }, // D
    Vertex { position: [0.44147372, 0.2347359, 0.0], color: [0.5, 0.0, 0.5] }, // E
];

const INDICES: &[u16] = &[
    0, 1, 4,
    1, 2, 4,
    2, 3, 4,
];

struct State<'a> {
    surface: wgpu::Surface<'a>,
    device: wgpu::Device,
    queue: wgpu::Queue,
    config: wgpu::SurfaceConfiguration,
    size: winit::dpi::PhysicalSize<u32>,
    // The window must be declared after the surface so
    // it gets dropped after it as the surface contains
    // unsafe references to the window's resources.
    window: &'a Window,
    render_pipeline: wgpu::RenderPipeline,
    vertex_buffer: wgpu::Buffer,
    index_buffer: wgpu::Buffer,
    num_indices: u32,
}

impl<'a> State<'a> {
    // Creating some of the wgpu types requires async code
    async fn new(window: &'a Window) -> State<'a> {
        let size = window.inner_size();
        let num_vertices = VERTICES.len() as u32;

        // The instance is a handle to our GPU
        // Backends::all => Vulkan + Metal + DX12 + Browser WebGPU
        let instance = wgpu::Instance::new(wgpu::InstanceDescriptor {
            // TODO: Change this when enabling switchable graphics for the user
            // If this is not for the web, we can use Vulkan + Metal + DX12
            #[cfg(not(target_arch="wasm32"))]
            backends: wgpu::Backends::PRIMARY,
            // TODO: Probably remove this, because WebAssembly won't be used for the foreseeable future
            #[cfg(target_arch="wasm32")]
            backends: wgpu::Backends::GL,
            ..Default::default()
        });

        let surface = instance.create_surface(window).unwrap();

        // This checks all the adapters on a machine and returns an iterator
        /*let adapter = instance
            .enumerate_adapters(wgpu::Backends::all())
            .filter(|adapter| {
                // Check if this adapter supports our surface
                adapter.is_surface_supported(&surface)
            })
            .next()
            .unwrap()*/

        // TODO: Include Telemetry to see how many users WGPU chooses a suboptimal adapter for
        let adapter = instance.request_adapter(
            &wgpu::RequestAdapterOptions {
                power_preference: wgpu::PowerPreference::default(),
                compatible_surface: Some(&surface),
                force_fallback_adapter: false,
            },
        ).await.unwrap();

        log::info!("Adapter: {:?}", adapter.get_info());

        // List of all features the current device supports
        // let features = adapter.features();

        let (device, queue) = adapter.request_device(
            &wgpu::DeviceDescriptor {
                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.
                // TODO: Probably remove check for wasm32, because WebAssembly won't be used for the foreseeable future
                required_limits: if cfg!(target_arch = "wasm32") {
                    wgpu::Limits::downlevel_webgl2_defaults()
                } else {
                    wgpu::Limits::default()
                },
                label: None,
                // Default is performance, which requires more memory, but is faster
                memory_hints: Default::default(),
            },
            None, // Trace path
        ).await.unwrap();

        let surface_caps = surface.get_capabilities(&adapter);
        // Shader code assumes an sRGB surface texture. Using a different
        // one will result in all the colors coming 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()
            .find(|f| f.is_srgb())
            .copied()
            .unwrap_or(surface_caps.formats[0]);

        log::info!("Surface format: {:?}", surface_format);
        log::info!("Surface present modes: {:?}", surface_caps.present_modes);
        log::info!("Surface alpha modes: {:?}", surface_caps.alpha_modes);

        let config = wgpu::SurfaceConfiguration {
            usage: wgpu::TextureUsages::RENDER_ATTACHMENT,
            format: surface_format,
            width: size.width,
            height: size.height,
            // PresentMod::Fifo => VSync (Always supported)
            present_mode: surface_caps.present_modes[0],
            alpha_mode: surface_caps.alpha_modes[0],
            view_formats: vec![],
            desired_maximum_frame_latency: 2,
        };

        let render_pipeline_layout =
            device.create_pipeline_layout(&wgpu::PipelineLayoutDescriptor {
                label: Some("Render Pipeline Layout"),
                bind_group_layouts: &[],
                push_constant_ranges: &[],
            });

        let shader = device.create_shader_module(wgpu::ShaderModuleDescriptor {
            label: Some("Shader"),
            source: wgpu::ShaderSource::Wgsl(include_str!("shader.wgsl").into()),
        });

        let render_pipeline = device.create_render_pipeline(&wgpu::RenderPipelineDescriptor {
            label: Some("Render Pipeline"),
            layout: Some(&render_pipeline_layout),
            vertex: wgpu::VertexState {
                module: &shader,
                entry_point: "vs_main",
                buffers: &[Vertex::desc()],
                compilation_options: Default::default(),
            },
            fragment: Some(wgpu::FragmentState {
                module: &shader,
                entry_point: "fs_main",
                targets: &[Some(wgpu::ColorTargetState {
                    format: config.format,
                    blend: Some(wgpu::BlendState::REPLACE),
                    write_mask: wgpu::ColorWrites::ALL,
                })],
                compilation_options: wgpu::PipelineCompilationOptions::default(),
            }),
            primitive: wgpu::PrimitiveState {
                topology: wgpu::PrimitiveTopology::TriangleList,
                strip_index_format: None,
                front_face: wgpu::FrontFace::Ccw,
                cull_mode: Some(wgpu::Face::Back),
                // Setting this to anything other than Fill requires Features::NON_FILL_POLYGON_MODE
                polygon_mode: wgpu::PolygonMode::Fill,
                // Requires Features::DEPTH_CLIP_CONTROL
                unclipped_depth: false,
                // Requires Features::CONSERVATIVE_RASTERIZATION
                conservative: false,
            },
            depth_stencil: None,
            multisample: wgpu::MultisampleState {
                count: 1,
                mask: !0,
                alpha_to_coverage_enabled: false,
            },
            multiview: None,
            cache: None,
        });

        let vertex_buffer = device.create_buffer_init(
            &wgpu::util::BufferInitDescriptor {
                label: Some("Vertex Buffer"),
                contents: bytemuck::cast_slice(VERTICES),
                usage: wgpu::BufferUsages::VERTEX,
            }
        );

        let index_buffer = device.create_buffer_init(
            &wgpu::util::BufferInitDescriptor {
                label: Some("Index Buffer"),
                contents: bytemuck::cast_slice(INDICES),
                usage: wgpu::BufferUsages::INDEX,
            }
        );
        let num_indices = INDICES.len() as u32;

        Self {
            window,
            surface,
            device,
            queue,
            config,
            size,
            render_pipeline,
            vertex_buffer,
            index_buffer,
            num_indices,
        }
    }

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

    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 {
        // Change color on mouse move
        match event {
            WindowEvent::CursorMoved { position, .. } => {
                /*let size = self.size;
                let color = wgpu::Color {
                    r: position.x as f64 / size.width as f64,
                    g: position.y as f64 / size.height as f64,
                    b: 0.3,
                    a: 1.0,
                };

                let output = self.surface.get_current_texture().unwrap();
                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(color),
                                store: wgpu::StoreOp::Store,
                            },
                        })],
                        depth_stencil_attachment: None,
                        occlusion_query_set: None,
                        timestamp_writes: None,
                    });
                }

                self.queue.submit(std::iter::once(encoder.finish()));
                output.present();
                return true;*/
                false
            }
            WindowEvent::KeyboardInput {
                event:
                KeyEvent {
                    state: ElementState::Pressed,
                    physical_key: PhysicalKey::Code(KeyCode::Space),
                    ..
                },
                ..
            } => {
                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 mut render_pass = encoder.begin_render_pass(&wgpu::RenderPassDescriptor {
                label: Some("Render Pass"),
                color_attachments: &[
                    // This is what @location(0) in the fragment shader targets
                    Some(wgpu::RenderPassColorAttachment {
                        view: &view,
                        resolve_target: None,
                        ops: wgpu::Operations {
                            load: wgpu::LoadOp::Clear(
                                wgpu::Color {
                                    r: 0.1,
                                    g: 0.2,
                                    b: 0.3,
                                    a: 1.0,
                                }
                            ),
                            store: wgpu::StoreOp::Store,
                        }
                    })
                ],
                depth_stencil_attachment: None,
                occlusion_query_set: None,
                timestamp_writes: None,
            });

            render_pass.set_pipeline(&self.render_pipeline);
            render_pass.set_vertex_buffer(0, self.vertex_buffer.slice(..));
            render_pass.set_index_buffer(self.index_buffer.slice(..), wgpu::IndexFormat::Uint16);
            render_pass.draw_indexed(0..self.num_indices, 0, 0..1);
        }

        // submit will accept anything that implements IntoIter
        self.queue.submit(std::iter::once(encoder.finish()));
        output.present();

        Ok(())
    }
}

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

    let mut state = State::new(&window).await;
    // Variable used to prevent rendering before the surface is configured
    let mut surface_configured = false;

    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) => {
                        surface_configured = true;
                        state.resize(*physical_size);
                    }

                    WindowEvent::RedrawRequested => {
                        // This tells winit that we want another frame after this one
                        state.window().request_redraw();

                        if !surface_configured {
                            return;
                        }

                        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();
                            }

                            // This happens when the a frame takes too long to present
                            Err(wgpu::SurfaceError::Timeout) => {
                                log::warn!("Surface timeout")
                            }
                        }
                    }
                    _ => {}
                }
            }
            _ => {}
        }
    }).expect("Event loop crashed unexpectedly");
}