use core::iter;
use nalgebra::{Point3, Vector3};
use std::sync::Arc;
use std::time::Instant;

use pollster::block_on;
use wgpu::util::DeviceExt;
use winit::{
    dpi::LogicalSize,
    event::{ElementState, Event, WindowEvent},
    event_loop::{ControlFlow, EventLoop},
    window::Window,
};

use crate::light::Light;
use crate::primitive::Material;
use crate::{camera::Camera, primitive::*, raytracer, scene::Scene};

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,
                },
            ],
        }
    }
}

pub struct State {
    surface: wgpu::Surface,
    device: wgpu::Device,
    queue: wgpu::Queue,
    config: wgpu::SurfaceConfiguration,
    pub size: winit::dpi::PhysicalSize<u32>,
    render_pipeline: wgpu::RenderPipeline,
    vertex_buffer: wgpu::Buffer,
    index_buffer: wgpu::Buffer,
    window: Window,
}

impl State {
    pub async fn new(window: Window) -> 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 {
            backends: wgpu::Backends::all(),
            ..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 = unsafe { 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,
                    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.
                    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],
            view_formats: vec![],
        };
        surface.configure(&device, &config);

        let shader = device.create_shader_module(wgpu::ShaderModuleDescriptor {
            label: Some("Shader"),
            source: wgpu::ShaderSource::Wgsl(include_str!("2d.wgsl").into()),
        });

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

        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()],
            },
            fragment: Some(wgpu::FragmentState {
                module: &shader,
                entry_point: "fs_main",
                targets: &[Some(wgpu::ColorTargetState {
                    format: config.format,
                    blend: Some(wgpu::BlendState {
                        color: wgpu::BlendComponent::REPLACE,
                        alpha: wgpu::BlendComponent::REPLACE,
                    }),
                    write_mask: wgpu::ColorWrites::ALL,
                })],
            }),
            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::POLYGON_MODE_LINE
                // or Features::POLYGON_MODE_POINT
                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,
            },
            // If the pipeline will be used with a multiview render pass, this
            // indicates how many array layers the attachments will have.
            multiview: None,
        });

        let vertex_buffer = device.create_buffer_init(&wgpu::util::BufferInitDescriptor {
            label: Some("Vertex Buffer"),
            contents: &[1],
            usage: wgpu::BufferUsages::VERTEX,
        });
        let index_buffer = device.create_buffer_init(&wgpu::util::BufferInitDescriptor {
            label: Some("Index Buffer"),
            contents: &[1],
            usage: wgpu::BufferUsages::INDEX,
        });

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

    pub 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);
        }
    }

    #[allow(unused_variables)]
    pub fn input(&mut self, event: &WindowEvent) -> bool {
        false
    }

    pub fn update(&mut self) {}

    pub 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: &[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);
        }

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

        Ok(())
    }
}