// Credit of most code to https://sotrh.github.io/learn-wgpu/ since I'm not familiar with wgpu
use std::sync::Arc;

#[cfg(target_arch = "wasm32")]
use wasm_bindgen::prelude::*;
use winit::dpi::PhysicalPosition;
#[cfg(target_arch = "wasm32")]
use winit::platform::web::EventLoopExtWebSys;
use winit::{
  application::ApplicationHandler,
  event::*,
  event_loop::{ActiveEventLoop, EventLoop},
  keyboard::{KeyCode, PhysicalKey},
  window::Window,
};

// This will store the state of our game
pub struct State {
  surface: wgpu::Surface<'static>,
  device: wgpu::Device,
  queue: wgpu::Queue,
  config: wgpu::SurfaceConfiguration,
  is_surface_configured: bool,
  window: Arc<Window>,
  render_pipeline1: wgpu::RenderPipeline,
  render_pipeline2: wgpu::RenderPipeline,
  other_pipeline: bool,
  sky: wgpu::Color,
}

impl State {
  // We don't need this to be async right now,
  // but we will in the next tutorial
  pub async fn new(window: Arc<Window>) -> anyhow::Result<Self> {
    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 {
      #[cfg(not(target_arch = "wasm32"))]
      backends: wgpu::Backends::PRIMARY,
      #[cfg(target_arch = "wasm32")]
      backends: wgpu::Backends::GL,
      flags: Default::default(),
      memory_budget_thresholds: Default::default(),
      backend_options: Default::default(),
      display: None,
    });

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

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

    let (device, queue) = adapter
      .request_device(&wgpu::DeviceDescriptor {
        label: None,
        required_features: wgpu::Features::empty(),
        experimental_features: wgpu::ExperimentalFeatures::disabled(),
        // 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()
        },
        memory_hints: Default::default(),
        trace: wgpu::Trace::Off,
      })
      .await?;

    let surface_caps = surface.get_capabilities(&adapter);
    // Shader code in this tutorial 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]);
    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],
      view_formats: vec![],
      desired_maximum_frame_latency: 2,
    };

    let shader1 = device.create_shader_module(wgpu::include_wgsl!("assets/shader.wgsl"));

    let render_pipeline_layout1 =
      device.create_pipeline_layout(&wgpu::PipelineLayoutDescriptor {
        label: Some("Render Pipeline Layout"),
        bind_group_layouts: &[],
        immediate_size: 0,
      });

    let render_pipeline1 = device.create_render_pipeline(&wgpu::RenderPipelineDescriptor {
      label: Some("Render Pipeline"),
      layout: Some(&render_pipeline_layout1),
      vertex: wgpu::VertexState {
        module: &shader1,
        entry_point: Some("vs_main"), // 1.
        buffers: &[],                 // 2.
        compilation_options: wgpu::PipelineCompilationOptions::default(),
      },
      fragment: Some(wgpu::FragmentState {
        // 3.
        module: &shader1,
        entry_point: Some("fs_main"),
        targets: &[Some(wgpu::ColorTargetState {
          // 4.
          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, // 1.
        strip_index_format: None,
        front_face: wgpu::FrontFace::Ccw, // 2.
        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, // 1.
      multisample: wgpu::MultisampleState {
        count: 1,                         // 2.
        mask: !0,                         // 3.
        alpha_to_coverage_enabled: false, // 4.
      },
      multiview_mask: None, // 5.
      cache: None,          // 6.
    });

    let shader2 = device.create_shader_module(wgpu::include_wgsl!("assets/shader2.wgsl"));

    let render_pipeline_layout2 =
      device.create_pipeline_layout(&wgpu::PipelineLayoutDescriptor {
        label: Some("Render Pipeline Layout"),
        bind_group_layouts: &[],
        immediate_size: 0,
      });

    let render_pipeline2 = device.create_render_pipeline(&wgpu::RenderPipelineDescriptor {
      label: Some("Render Pipeline"),
      layout: Some(&render_pipeline_layout2),
      vertex: wgpu::VertexState {
        module: &shader2,
        entry_point: Some("vs_main"), // 1.
        buffers: &[],                 // 2.
        compilation_options: wgpu::PipelineCompilationOptions::default(),
      },
      fragment: Some(wgpu::FragmentState {
        // 3.
        module: &shader2,
        entry_point: Some("fs_main"),
        targets: &[Some(wgpu::ColorTargetState {
          // 4.
          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, // 1.
        strip_index_format: None,
        front_face: wgpu::FrontFace::Ccw, // 2.
        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, // 1.
      multisample: wgpu::MultisampleState {
        count: 1,                         // 2.
        mask: !0,                         // 3.
        alpha_to_coverage_enabled: false, // 4.
      },
      multiview_mask: None, // 5.
      cache: None,          // 6.
    });

    Ok(Self {
      surface,
      device,
      queue,
      config,
      is_surface_configured: false,
      window,
      render_pipeline1,
      render_pipeline2,
      other_pipeline: false,
      sky: wgpu::Color {
        r: 0.1,
        g: 0.2,
        b: 0.3,
        a: 1.0,
      },
    })
  }

  pub fn resize(&mut self, width: u32, height: u32) {
    if width > 0 && height > 0 {
      let max = 2048;
      self.config.width = width.min(max);
      self.config.height = height.min(max);
      self.surface.configure(&self.device, &self.config);
      self.is_surface_configured = true;
    }
  }

  fn update(&mut self) {
    // ...
  }

  fn render(&mut self) -> anyhow::Result<()> {
    self.window.request_redraw();

    // We can't render unless the surface is configured
    if !self.is_surface_configured {
      return Ok(());
    }

    let output = match self.surface.get_current_texture() {
      wgpu::CurrentSurfaceTexture::Success(surface_texture) => surface_texture,
      wgpu::CurrentSurfaceTexture::Suboptimal(surface_texture) => {
        self.surface.configure(&self.device, &self.config);
        surface_texture
      }
      wgpu::CurrentSurfaceTexture::Timeout
      | wgpu::CurrentSurfaceTexture::Occluded
      | wgpu::CurrentSurfaceTexture::Validation => {
        // Skip this frame
        return Ok(());
      }
      wgpu::CurrentSurfaceTexture::Outdated => {
        self.surface.configure(&self.device, &self.config);
        return Ok(());
      }
      wgpu::CurrentSurfaceTexture::Lost => {
        // You could recreate the devices and all resources
        // created with it here, but we'll just bail
        anyhow::bail!("Lost device");
      }
    };
    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: &[Some(wgpu::RenderPassColorAttachment {
          view: &view,
          resolve_target: None,
          depth_slice: None,
          ops: wgpu::Operations {
            load: wgpu::LoadOp::Clear(self.sky),
            store: wgpu::StoreOp::Store,
          },
        })],
        depth_stencil_attachment: None,
        occlusion_query_set: None,
        timestamp_writes: None,
        multiview_mask: None,
      });

      if self.other_pipeline {
        render_pass.set_pipeline(&self.render_pipeline1);
      } else {
        render_pass.set_pipeline(&self.render_pipeline2);
      }
      render_pass.draw(0..3, 0..1); // 3.
    }

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

    Ok(())
  }

  fn handle_key(&mut self, event_loop: &ActiveEventLoop, code: KeyCode, is_pressed: bool) {
    match (code, is_pressed) {
      (KeyCode::Escape, true) => event_loop.exit(),
      (KeyCode::Space, true) => {
        self.other_pipeline = !self.other_pipeline;
      }
      _ => {}
    }
  }

  fn handle_mouse_moved(&mut self, position: PhysicalPosition<f64>) {
    self.sky = wgpu::Color {
      r: 0.3,
      g: position.x / 1000.0,
      b: position.y / 1000.0,
      a: 1.0,
    }
  }
}

pub struct App {
  #[cfg(target_arch = "wasm32")]
  proxy: Option<winit::event_loop::EventLoopProxy<State>>,
  state: Option<State>,
}

impl App {
  pub fn new(#[cfg(target_arch = "wasm32")] event_loop: &EventLoop<State>) -> Self {
    #[cfg(target_arch = "wasm32")]
    let proxy = Some(event_loop.create_proxy());
    Self {
      state: None,
      #[cfg(target_arch = "wasm32")]
      proxy,
    }
  }
}

impl ApplicationHandler<State> for App {
  fn resumed(&mut self, event_loop: &ActiveEventLoop) {
    #[allow(unused_mut)]
    let mut window_attributes = Window::default_attributes();

    #[cfg(target_arch = "wasm32")]
    {
      use wasm_bindgen::JsCast;
      use winit::platform::web::WindowAttributesExtWebSys;

      const CANVAS_ID: &str = "canvas";

      let window = wgpu::web_sys::window().unwrap_throw();
      let document = window.document().unwrap_throw();
      let canvas = document.get_element_by_id(CANVAS_ID).unwrap_throw();
      let html_canvas_element = canvas.unchecked_into();
      window_attributes = window_attributes.with_canvas(Some(html_canvas_element));
    }

    let window = Arc::new(event_loop.create_window(window_attributes).unwrap());

    #[cfg(not(target_arch = "wasm32"))]
    {
      // If we are not on web we can use pollster to
      // await the window creation
      self.state = Some(pollster::block_on(State::new(window)).unwrap());
    }

    #[cfg(target_arch = "wasm32")]
    {
      // Run the future asynchronously and use the
      // proxy to send the results to the event loop
      if let Some(proxy) = self.proxy.take() {
        wasm_bindgen_futures::spawn_local(async move {
          assert!(
            proxy
              .send_event(
                State::new(window)
                  .await
                  .expect("Unable to create canvas!!!")
              )
              .is_ok()
          )
        });
      }
    }
  }

  #[allow(unused_mut)]
  fn user_event(&mut self, _event_loop: &ActiveEventLoop, mut event: State) {
    // This is where proxy.send_event() ends up
    #[cfg(target_arch = "wasm32")]
    {
      event.window.request_redraw();
      event.resize(
        event.window.inner_size().width,
        event.window.inner_size().height,
      );
    }
    self.state = Some(event);
  }

  fn window_event(
    &mut self,
    event_loop: &ActiveEventLoop,
    _window_id: winit::window::WindowId,
    event: WindowEvent,
  ) {
    let state = match &mut self.state {
      Some(canvas) => canvas,
      None => return,
    };

    match event {
      WindowEvent::CloseRequested => event_loop.exit(),
      WindowEvent::Resized(size) => state.resize(size.width, size.height),
      WindowEvent::RedrawRequested => {
        state.update();
        match state.render() {
          Ok(_) => {}
          Err(e) => {
            // Log the error and exit gracefully
            log::error!("{e}");
            event_loop.exit();
          }
        }
      }
      WindowEvent::CursorMoved { position: pos, .. } => state.handle_mouse_moved(pos),
      WindowEvent::KeyboardInput {
        event:
        KeyEvent {
          physical_key: PhysicalKey::Code(code),
          state: key_state,
          ..
        },
        ..
      } => state.handle_key(event_loop, code, key_state.is_pressed()),
      _ => {}
    }
  }
}

pub fn run() -> anyhow::Result<()> {
  #[cfg(not(target_arch = "wasm32"))]
  {
    env_logger::init();
  }
  #[cfg(target_arch = "wasm32")]
  {
    console_log::init_with_level(log::Level::Info).unwrap_throw();
  }

  let event_loop = EventLoop::with_user_event().build()?;
  #[cfg(not(target_arch = "wasm32"))]
  {
    let mut app = App::new();
    event_loop.run_app(&mut app)?;
  }
  #[cfg(target_arch = "wasm32")]
  {
    let app = App::new(&event_loop);
    event_loop.spawn_app(app);
  }

  Ok(())
}

#[cfg(target_arch = "wasm32")]
#[wasm_bindgen(start)]
pub fn run_web() -> Result<(), wasm_bindgen::JsValue> {
  console_error_panic_hook::set_once();
  run().unwrap_throw();

  Ok(())
}