mod camera;
mod texture;
mod uniforms;

use image::GenericImageView;
use std::{iter, mem::size_of, num::NonZeroU32, time::Instant};
use wgpu::{util::DeviceExt, BufferAddress};
use winit::{
    event::{ElementState, Event, KeyboardInput, VirtualKeyCode, WindowEvent},
    event_loop::{ControlFlow, EventLoop},
    window::{Window, WindowBuilder},
};

use crate::{camera::Camera, texture::Texture, uniforms::Uniforms};

#[repr(C)]
#[derive(Copy, Clone, Debug, bytemuck::Pod, bytemuck::Zeroable)]
struct Vertex {
    position: [f32; 3],
    texture_coordinates: [f32; 2],
}

impl Vertex {
    fn desc<'a>() -> wgpu::VertexBufferLayout<'a> {
        wgpu::VertexBufferLayout {
            array_stride: size_of::<Vertex>() as BufferAddress,
            step_mode: wgpu::InputStepMode::Vertex,
            attributes: &[
                wgpu::VertexAttribute {
                    offset: 0,
                    shader_location: 0,
                    format: wgpu::VertexFormat::Float32x3,
                },
                wgpu::VertexAttribute {
                    offset: size_of::<[f32; 3]>() as BufferAddress,
                    shader_location: 1,
                    format: wgpu::VertexFormat::Float32x2,
                },
            ],
        }
    }
}

const VERTICES: &[Vertex] = &[
    Vertex {
        position: [-0.5, -0.5, -0.5],
        texture_coordinates: [0.0, 0.0],
    }, // 0
    Vertex {
        position: [-0.5, -0.5, 0.5],
        texture_coordinates: [0.0, 1.0],
    }, // 1
    Vertex {
        position: [-0.5, 0.5, 0.5],
        texture_coordinates: [1.0, 1.0],
    }, // 2
    Vertex {
        position: [-0.5, 0.5, -0.5],
        texture_coordinates: [1.0, 0.0],
    }, // 3
    Vertex {
        position: [0.5, -0.5, -0.5],
        texture_coordinates: [1.0, 1.0],
    }, // 4
    Vertex {
        position: [0.5, -0.5, 0.5],
        texture_coordinates: [1.0, 0.0],
    }, // 5
    Vertex {
        position: [0.5, 0.5, 0.5],
        texture_coordinates: [0.0, 0.0],
    }, // 6
    Vertex {
        position: [0.5, 0.5, -0.5],
        texture_coordinates: [0.0, 1.0],
    }, // 7
];

#[rustfmt::skip]
const INDICES: &[u16] = &[
    // left
    0, 1, 2,
    0, 2, 3,
    // bottom
    1, 0, 4,
    1, 4, 5,
    // right
    5, 7, 6,
    5, 4, 7,
    // top
    3, 2, 6,
    3, 6, 7,
    // front
    2, 1, 5,
    2, 5, 6,
    // back
    0, 3, 7,
    0, 7, 4,
];

struct State {
    surface: wgpu::Surface,
    device: wgpu::Device,
    queue: wgpu::Queue,
    sc_desc: wgpu::SwapChainDescriptor,
    swap_chain: wgpu::SwapChain,
    size: winit::dpi::PhysicalSize<u32>,
    render_pipeline: wgpu::RenderPipeline,
    vertex_buffer: wgpu::Buffer,
    index_buffer: wgpu::Buffer,
    num_indices: u32,
    dirt_diffuse_bind_group: wgpu::BindGroup,
    camera: Camera,
    uniforms: Uniforms,
    uniform_buffer: wgpu::Buffer,
    uniform_bind_group: wgpu::BindGroup,
}

impl State {
    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::BackendBit::PRIMARY);
        let surface = unsafe { instance.create_surface(window) };
        let adapter = instance
            .request_adapter(&wgpu::RequestAdapterOptions {
                power_preference: wgpu::PowerPreference::HighPerformance,
                compatible_surface: Some(&surface),
            })
            .await
            .unwrap();

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

        let swap_chain_descriptor = wgpu::SwapChainDescriptor {
            usage: wgpu::TextureUsage::RENDER_ATTACHMENT,
            format: adapter.get_swap_chain_preferred_format(&surface).unwrap(),
            width: size.width,
            height: size.height,
            present_mode: wgpu::PresentMode::Immediate,
        };
        let swap_chain = device.create_swap_chain(&surface, &swap_chain_descriptor);

        let dirt_diffuse_texture = Texture::from_bytes(
            &device,
            &queue,
            include_bytes!("../assets/block/dirt.png"),
            "dirt_diffuse",
        )
        .unwrap();

        let texture_bind_group_layout =
            device.create_bind_group_layout(&wgpu::BindGroupLayoutDescriptor {
                label: Some("exture_bind_group_layout"),
                entries: &[
                    wgpu::BindGroupLayoutEntry {
                        binding: 0,
                        visibility: wgpu::ShaderStage::FRAGMENT,
                        ty: wgpu::BindingType::Texture {
                            multisampled: false,
                            view_dimension: wgpu::TextureViewDimension::D2,
                            sample_type: wgpu::TextureSampleType::Float { filterable: true },
                        },
                        count: None,
                    },
                    wgpu::BindGroupLayoutEntry {
                        binding: 1,
                        visibility: wgpu::ShaderStage::FRAGMENT,
                        ty: wgpu::BindingType::Sampler {
                            comparison: false,
                            filtering: true,
                        },
                        count: None,
                    },
                ],
            });

        let dirt_diffuse_bind_group = device.create_bind_group(&wgpu::BindGroupDescriptor {
            label: Some("dirt_diffuse_bind_group"),
            layout: &texture_bind_group_layout,
            entries: &[
                wgpu::BindGroupEntry {
                    binding: 0,
                    resource: wgpu::BindingResource::TextureView(&dirt_diffuse_texture.view),
                },
                wgpu::BindGroupEntry {
                    binding: 1,
                    resource: wgpu::BindingResource::Sampler(&dirt_diffuse_texture.sampler),
                },
            ],
        });

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

        let camera = Camera {
            // position the camera one unit up and 2 units back
            // +z is out of the screen
            eye: (0.0, 1.0, 2.0).into(),
            // have it look at the origin
            target: (0.0, 0.0, 0.0).into(),
            // which way is "up"
            up: cgmath::Vector3::unit_y(),
            aspect: swap_chain_descriptor.width as f32 / swap_chain_descriptor.height as f32,
            fovy: 45.0,
            znear: 0.1,
            zfar: 100.0,
        };

        let mut uniforms = Uniforms::new();
        uniforms.update_view_proj(&camera);

        let uniform_buffer = device.create_buffer_init(&wgpu::util::BufferInitDescriptor {
            label: Some("Uniform Buffer"),
            contents: bytemuck::cast_slice(&[uniforms]),
            usage: wgpu::BufferUsage::UNIFORM | wgpu::BufferUsage::COPY_DST,
        });

        let uniform_bind_group_layout =
            device.create_bind_group_layout(&wgpu::BindGroupLayoutDescriptor {
                entries: &[wgpu::BindGroupLayoutEntry {
                    binding: 0,
                    visibility: wgpu::ShaderStage::VERTEX,
                    ty: wgpu::BindingType::Buffer {
                        ty: wgpu::BufferBindingType::Uniform,
                        has_dynamic_offset: false,
                        min_binding_size: None,
                    },
                    count: None,
                }],
                label: Some("uniform_bind_group_layout"),
            });

        let render_pipeline_layout =
            device.create_pipeline_layout(&wgpu::PipelineLayoutDescriptor {
                label: Some("Render Pipeline Layout"),
                bind_group_layouts: &[&texture_bind_group_layout, &uniform_bind_group_layout],
                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: "main",
                buffers: &[Vertex::desc()],
            },
            fragment: Some(wgpu::FragmentState {
                module: &shader,
                entry_point: "main",
                targets: &[wgpu::ColorTargetState {
                    format: swap_chain_descriptor.format,
                    blend: Some(wgpu::BlendState {
                        color: wgpu::BlendComponent::REPLACE,
                        alpha: wgpu::BlendComponent::REPLACE,
                    }),
                    write_mask: wgpu::ColorWrite::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::NON_FILL_POLYGON_MODE
                polygon_mode: wgpu::PolygonMode::Fill,
                // Requires Features::DEPTH_CLAMPING
                clamp_depth: false,
                // Requires Features::CONSERVATIVE_RASTERIZATION
                conservative: false,
            },
            depth_stencil: None,
            multisample: wgpu::MultisampleState {
                count: 1,
                mask: !0,
                alpha_to_coverage_enabled: false,
            },
        });

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

        let uniform_bind_group = device.create_bind_group(&wgpu::BindGroupDescriptor {
            layout: &uniform_bind_group_layout,
            entries: &[wgpu::BindGroupEntry {
                binding: 0,
                resource: uniform_buffer.as_entire_binding(),
            }],
            label: Some("uniform_bind_group"),
        });

        Self {
            surface,
            device,
            queue,
            sc_desc: swap_chain_descriptor,
            swap_chain,
            size,
            render_pipeline,
            vertex_buffer,
            index_buffer,
            num_indices,
            camera,
            uniforms,
            uniform_buffer,
            uniform_bind_group,
            dirt_diffuse_bind_group,
        }
    }

    fn resize(&mut self, new_size: winit::dpi::PhysicalSize<u32>) {
        println!("resizing to {:?}", new_size);
        self.size = new_size;
        self.sc_desc.width = new_size.width;
        self.sc_desc.height = new_size.height;
        self.swap_chain = self.device.create_swap_chain(&self.surface, &self.sc_desc);
    }

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

    fn update(&mut self) {}

    fn render(&mut self) -> Result<(), wgpu::SwapChainError> {
        let frame = self.swap_chain.get_current_frame()?.output;

        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: &[wgpu::RenderPassColorAttachment {
                    view: &frame.view,
                    resolve_target: None,
                    ops: wgpu::Operations {
                        load: wgpu::LoadOp::Clear(wgpu::Color::BLACK),
                        store: true,
                    },
                }],
                depth_stencil_attachment: None,
            });

            render_pass.set_pipeline(&self.render_pipeline);
            render_pass.set_bind_group(0, &self.dirt_diffuse_bind_group, &[]);
            render_pass.set_bind_group(1, &self.uniform_bind_group, &[]);
            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);
        }

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

        Ok(())
    }
}

fn main() {
    env_logger::init();
    let event_loop = EventLoop::new();
    let window = WindowBuilder::new()
        .with_title("\u{1f980}\u{1f980}\u{1f980}\u{1f980}\u{1f980}")
        .build(&event_loop)
        .unwrap();

    use futures::executor::block_on;

    // Since main can't be async, we're going to need to block
    let mut state = block_on(State::new(&window));

    let mut frames = 0;
    let mut instant = Instant::now();

    event_loop.run(move |event, _, control_flow| {
        match event {
            Event::WindowEvent {
                ref event,
                window_id,
            } if window_id == window.id() => {
                if !state.input(event) {
                    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,
                            _ => {}
                        },
                        WindowEvent::Resized(physical_size) => {
                            state.resize(*physical_size);
                        }
                        WindowEvent::ScaleFactorChanged { new_inner_size, .. } => {
                            // new_inner_size is &mut so w have to dereference it twice
                            state.resize(**new_inner_size);
                        }
                        _ => {}
                    }
                }
            }
            Event::RedrawRequested(_) => {
                frames += 1;
                if frames % 1000 == 0 {
                    let frametime = instant.elapsed() / 1000;
                    let fps = 1_000_000 / frametime.as_micros();
                    println!("{:?} - {} fps", frametime, fps);
                    instant = Instant::now();
                }

                state.update();
                match state.render() {
                    Ok(_) => {}
                    // Recreate the swap_chain if lost
                    Err(wgpu::SwapChainError::Lost) => state.resize(state.size),
                    // The system is out of memory, we should probably quit
                    Err(wgpu::SwapChainError::OutOfMemory) => *control_flow = ControlFlow::Exit,
                    // All other errors (Outdated, Timeout) should be resolved by the next frame
                    Err(e) => eprintln!("{:?}", e),
                }
            }
            Event::MainEventsCleared => {
                // RedrawRequested will only trigger once, unless we manually
                // request it.
                window.request_redraw();
            }
            _ => {}
        }
    });
}