use cgmath::prelude::*;
use rayon::prelude::*;
use std::iter;
use wgpu::util::DeviceExt;
use winit::{
    dpi::PhysicalPosition,
    event::*,
    event_loop::{ControlFlow, EventLoop},
    window::Window,
};

mod camera;
mod model;
mod pipeline; // NEW!
mod texture;

use model::{DrawLight, DrawModel, Vertex};
use pipeline::create_render_pipeline;

const NUM_INSTANCES_PER_ROW: u32 = 10;

#[repr(C)]
#[derive(Copy, Clone, bytemuck::Pod, bytemuck::Zeroable)]
struct Uniforms {
    view_position: [f32; 4],
    view_proj: [[f32; 4]; 4],
}

impl Uniforms {
    fn new() -> Self {
        Self {
            view_position: [0.0; 4],
            view_proj: cgmath::Matrix4::identity().into(),
        }
    }

    // UPDATED!
    fn update_view_proj(&mut self, camera: &camera::Camera, projection: &camera::Projection) {
        self.view_position = camera.position.to_homogeneous().into();
        self.view_proj = (projection.calc_matrix() * camera.calc_matrix()).into()
    }
}

struct Instance {
    position: cgmath::Vector3<f32>,
    rotation: cgmath::Quaternion<f32>,
}

impl Instance {
    fn to_raw(&self) -> InstanceRaw {
        InstanceRaw {
            model: (cgmath::Matrix4::from_translation(self.position)
                * cgmath::Matrix4::from(self.rotation))
            .into(),
        }
    }
}

#[repr(C)]
#[derive(Debug, Copy, Clone, bytemuck::Pod, bytemuck::Zeroable)]
struct InstanceRaw {
    #[allow(dead_code)]
    model: [[f32; 4]; 4],
}

impl model::Vertex for InstanceRaw {
    fn desc<'a>() -> wgpu::VertexBufferLayout<'a> {
        use std::mem;
        wgpu::VertexBufferLayout {
            array_stride: mem::size_of::<InstanceRaw>() as wgpu::BufferAddress,
            // We need to switch from using a step mode of Vertex to Instance
            // This means that our shaders will only change to use the next
            // instance when the shader starts processing a new instance
            step_mode: wgpu::InputStepMode::Instance,
            attributes: &[
                wgpu::VertexAttribute {
                    offset: 0,
                    // While our vertex shader only uses locations 0, and 1 now, in later tutorials we'll
                    // be using 2, 3, and 4, for Vertex. We'll start at slot 5 not conflict with them later
                    shader_location: 5,
                    format: wgpu::VertexFormat::Float32x4,
                },
                // A mat4 takes up 4 vertex slots as it is technically 4 vec4s. We need to define a slot
                // for each vec4. We don't have to do this in code though.
                wgpu::VertexAttribute {
                    offset: mem::size_of::<[f32; 4]>() as wgpu::BufferAddress,
                    shader_location: 6,
                    format: wgpu::VertexFormat::Float32x4,
                },
                wgpu::VertexAttribute {
                    offset: mem::size_of::<[f32; 8]>() as wgpu::BufferAddress,
                    shader_location: 7,
                    format: wgpu::VertexFormat::Float32x4,
                },
                wgpu::VertexAttribute {
                    offset: mem::size_of::<[f32; 12]>() as wgpu::BufferAddress,
                    shader_location: 8,
                    format: wgpu::VertexFormat::Float32x4,
                },
            ],
        }
    }
}

#[repr(C)]
#[derive(Debug, Copy, Clone, bytemuck::Pod, bytemuck::Zeroable)]
struct Light {
    position: [f32; 3],
    // Due to uniforms requiring 16 byte (4 float) spacing, we need to use a padding field here
    _padding: u32,
    color: [f32; 3],
}

struct State {
    surface: wgpu::Surface,
    device: wgpu::Device,
    queue: wgpu::Queue,
    sc_desc: wgpu::SwapChainDescriptor,
    swap_chain: wgpu::SwapChain,
    render_pipeline: wgpu::RenderPipeline,
    obj_model: model::Model,
    camera: camera::Camera,
    projection: camera::Projection,
    camera_controller: camera::CameraController,
    uniforms: Uniforms,
    uniform_buffer: wgpu::Buffer,
    uniform_bind_group: wgpu::BindGroup,
    instances: Vec<Instance>,
    #[allow(dead_code)]
    instance_buffer: wgpu::Buffer,
    depth_texture: texture::Texture,
    size: winit::dpi::PhysicalSize<u32>,
    light: Light,
    light_buffer: wgpu::Buffer,
    light_bind_group: wgpu::BindGroup,
    light_render_pipeline: wgpu::RenderPipeline,
    #[allow(dead_code)]
    debug_material: model::Material,
    last_mouse_pos: PhysicalPosition<f64>,
    mouse_pressed: bool,
}

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::default(),
                compatible_surface: Some(&surface),
            })
            .await
            .unwrap();
        let path = std::path::Path::new("trace");
        let (device, queue) = adapter
            .request_device(
                &wgpu::DeviceDescriptor {
                    label: None,
                    features: wgpu::Features::empty(),
                    limits: wgpu::Limits::default(),
                },
                Some(&path), // Trace path
            )
            .await
            .unwrap();

        let sc_desc = 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::Fifo,
        };

        let swap_chain = device.create_swap_chain(&surface, &sc_desc);

        let texture_bind_group_layout =
            device.create_bind_group_layout(&wgpu::BindGroupLayoutDescriptor {
                entries: &[
                    wgpu::BindGroupLayoutEntry {
                        binding: 0,
                        visibility: wgpu::ShaderStage::FRAGMENT,
                        ty: wgpu::BindingType::Texture {
                            multisampled: false,
                            sample_type: wgpu::TextureSampleType::Float { filterable: true },
                            view_dimension: wgpu::TextureViewDimension::D2,
                        },
                        count: None,
                    },
                    wgpu::BindGroupLayoutEntry {
                        binding: 1,
                        visibility: wgpu::ShaderStage::FRAGMENT,
                        ty: wgpu::BindingType::Sampler {
                            comparison: false,
                            filtering: true,
                        },
                        count: None,
                    },
                    // normal map
                    wgpu::BindGroupLayoutEntry {
                        binding: 2,
                        visibility: wgpu::ShaderStage::FRAGMENT,
                        ty: wgpu::BindingType::Texture {
                            multisampled: false,
                            sample_type: wgpu::TextureSampleType::Float { filterable: true },
                            view_dimension: wgpu::TextureViewDimension::D2,
                        },
                        count: None,
                    },
                    wgpu::BindGroupLayoutEntry {
                        binding: 3,
                        visibility: wgpu::ShaderStage::FRAGMENT,
                        ty: wgpu::BindingType::Sampler {
                            comparison: false,
                            filtering: true,
                        },
                        count: None,
                    },
                ],
                label: Some("texture_bind_group_layout"),
            });

        // UPDATED!
        let camera = camera::Camera::new((0.0, 5.0, 10.0), cgmath::Deg(-90.0), cgmath::Deg(-20.0));
        let projection =
            camera::Projection::new(sc_desc.width, sc_desc.height, cgmath::Deg(45.0), 0.1, 100.0);
        let camera_controller = camera::CameraController::new(4.0, 0.4);

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

        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,
        });

        const SPACE_BETWEEN: f32 = 3.0;
        let instances = (0..NUM_INSTANCES_PER_ROW)
            .into_par_iter() // NEW!
            .flat_map(|z| {
                // UPDATED!
                (0..NUM_INSTANCES_PER_ROW).into_par_iter().map(move |x| {
                    let x = SPACE_BETWEEN * (x as f32 - NUM_INSTANCES_PER_ROW as f32 / 2.0);
                    let z = SPACE_BETWEEN * (z as f32 - NUM_INSTANCES_PER_ROW as f32 / 2.0);

                    let position = cgmath::Vector3 { x, y: 0.0, z };

                    let rotation = if position.is_zero() {
                        cgmath::Quaternion::from_axis_angle(
                            cgmath::Vector3::unit_z(),
                            cgmath::Deg(0.0),
                        )
                    } else {
                        cgmath::Quaternion::from_axis_angle(
                            position.clone().normalize(),
                            cgmath::Deg(45.0),
                        )
                    };

                    Instance { position, rotation }
                })
            })
            .collect::<Vec<_>>();

        let instance_data = instances.iter().map(Instance::to_raw).collect::<Vec<_>>();
        let instance_buffer = device.create_buffer_init(&wgpu::util::BufferInitDescriptor {
            label: Some("Instance Buffer"),
            contents: bytemuck::cast_slice(&instance_data),
            usage: wgpu::BufferUsage::VERTEX,
        });

        let uniform_bind_group_layout =
            device.create_bind_group_layout(&wgpu::BindGroupLayoutDescriptor {
                entries: &[wgpu::BindGroupLayoutEntry {
                    binding: 0,
                    visibility: wgpu::ShaderStage::VERTEX | wgpu::ShaderStage::FRAGMENT,
                    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 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"),
        });

        let res_dir = std::path::Path::new(env!("OUT_DIR")).join("res");
        let model_loader = model::ModelLoader::new(&device);

        // UPDATED!
        let obj_model = model_loader
            .load(
                &device,
                &queue,
                &texture_bind_group_layout,
                res_dir.join("cube.obj"),
            )
            .unwrap();

        let light = Light {
            position: [2.0, 2.0, 2.0],
            _padding: 0,
            color: [1.0, 1.0, 1.0],
        };

        let light_buffer = device.create_buffer_init(&wgpu::util::BufferInitDescriptor {
            label: Some("Light VB"),
            contents: bytemuck::cast_slice(&[light]),
            usage: wgpu::BufferUsage::UNIFORM | wgpu::BufferUsage::COPY_DST,
        });

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

        let light_bind_group = device.create_bind_group(&wgpu::BindGroupDescriptor {
            layout: &light_bind_group_layout,
            entries: &[wgpu::BindGroupEntry {
                binding: 0,
                resource: light_buffer.as_entire_binding(),
            }],
            label: None,
        });

        let depth_texture =
            texture::Texture::create_depth_texture(&device, &sc_desc, "depth_texture");

        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,
                    &light_bind_group_layout,
                ],
                push_constant_ranges: &[],
            });

        let render_pipeline = create_render_pipeline(
            &device,
            &render_pipeline_layout,
            sc_desc.format,
            Some(texture::Texture::DEPTH_FORMAT),
            &[model::ModelVertex::desc(), InstanceRaw::desc()],
            wgpu::include_spirv!("shader.vert.spv"),
            wgpu::include_spirv!("shader.frag.spv"),
        );

        let light_render_pipeline = {
            let layout = device.create_pipeline_layout(&wgpu::PipelineLayoutDescriptor {
                label: Some("Light Pipeline Layout"),
                bind_group_layouts: &[&uniform_bind_group_layout, &light_bind_group_layout],
                push_constant_ranges: &[],
            });

            create_render_pipeline(
                &device,
                &layout,
                sc_desc.format,
                Some(texture::Texture::DEPTH_FORMAT),
                &[model::ModelVertex::desc()],
                wgpu::include_spirv!("light.vert.spv"),
                wgpu::include_spirv!("light.frag.spv"),
            )
        };

        let debug_material = {
            let diffuse_bytes = include_bytes!("../res/cobble-diffuse.png");
            let normal_bytes = include_bytes!("../res/cobble-normal.png");

            let diffuse_texture = texture::Texture::from_bytes(
                &device,
                &queue,
                diffuse_bytes,
                "res/alt-diffuse.png",
                false,
            )
            .unwrap();
            let normal_texture = texture::Texture::from_bytes(
                &device,
                &queue,
                normal_bytes,
                "res/alt-normal.png",
                true,
            )
            .unwrap();

            model::Material::new(
                &device,
                "alt-material",
                diffuse_texture,
                normal_texture,
                &texture_bind_group_layout,
            )
        };

        Self {
            surface,
            device,
            queue,
            sc_desc,
            swap_chain,
            render_pipeline,
            obj_model,
            camera,
            projection,
            camera_controller,
            uniform_buffer,
            uniform_bind_group,
            uniforms,
            instances,
            instance_buffer,
            depth_texture,
            size,
            light,
            light_buffer,
            light_bind_group,
            light_render_pipeline,
            #[allow(dead_code)]
            debug_material,
            last_mouse_pos: (0.0, 0.0).into(),
            mouse_pressed: false,
        }
    }

    fn resize(&mut self, new_size: winit::dpi::PhysicalSize<u32>) {
        self.projection.resize(new_size.width, new_size.height);
        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);
        self.depth_texture =
            texture::Texture::create_depth_texture(&self.device, &self.sc_desc, "depth_texture");
    }

    fn input(&mut self, event: &WindowEvent) -> bool {
        match event {
            WindowEvent::KeyboardInput {
                input:
                    KeyboardInput {
                        virtual_keycode: Some(key),
                        state,
                        ..
                    },
                ..
            } => self.camera_controller.process_keyboard(*key, *state),
            WindowEvent::MouseWheel { delta, .. } => {
                self.camera_controller.process_scroll(delta);
                true
            }
            WindowEvent::MouseInput {
                button: MouseButton::Left,
                state,
                ..
            } => {
                self.mouse_pressed = *state == ElementState::Pressed;
                true
            }
            WindowEvent::CursorMoved { position, .. } => {
                let mouse_dx = position.x - self.last_mouse_pos.x;
                let mouse_dy = position.y - self.last_mouse_pos.y;
                self.last_mouse_pos = *position;
                if self.mouse_pressed {
                    self.camera_controller.process_mouse(mouse_dx, mouse_dy);
                }
                true
            }
            _ => false,
        }
    }

    fn update(&mut self, dt: std::time::Duration) {
        self.camera_controller.update_camera(&mut self.camera, dt);
        self.uniforms
            .update_view_proj(&self.camera, &self.projection);
        self.queue.write_buffer(
            &self.uniform_buffer,
            0,
            bytemuck::cast_slice(&[self.uniforms]),
        );

        // Update the light
        let old_position: cgmath::Vector3<_> = self.light.position.into();
        self.light.position =
            (cgmath::Quaternion::from_axis_angle((0.0, 1.0, 0.0).into(), cgmath::Deg(1.0))
                * old_position)
                .into();
        self.queue
            .write_buffer(&self.light_buffer, 0, bytemuck::cast_slice(&[self.light]));
    }

    fn render(&mut self) {
        let frame = self.swap_chain.get_current_frame();

        match frame {
            Ok(frame) => {
                let frame = 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 {
                                    r: 0.1,
                                    g: 0.2,
                                    b: 0.3,
                                    a: 1.0,
                                }),
                                store: true,
                            },
                        }],
                        depth_stencil_attachment: Some(wgpu::RenderPassDepthStencilAttachment {
                            view: &self.depth_texture.view,
                            depth_ops: Some(wgpu::Operations {
                                load: wgpu::LoadOp::Clear(1.0),
                                store: true,
                            }),
                            stencil_ops: None,
                        }),
                    });

                    render_pass.set_vertex_buffer(1, self.instance_buffer.slice(..));
                    render_pass.set_pipeline(&self.light_render_pipeline);
                    render_pass.draw_light_model(
                        &self.obj_model,
                        &self.uniform_bind_group,
                        &self.light_bind_group,
                    );

                    render_pass.set_pipeline(&self.render_pipeline);
                    render_pass.draw_model_instanced(
                        &self.obj_model,
                        0..self.instances.len() as u32,
                        &self.uniform_bind_group,
                        &self.light_bind_group,
                    );
                }
                self.queue.submit(iter::once(encoder.finish()));
            }
            Err(e) => {
                eprintln!("{:?}", e);
            }
        }
    }
}

fn main() {
    env_logger::init();
    let event_loop = EventLoop::new();
    let title = env!("CARGO_PKG_NAME");
    let window = winit::window::WindowBuilder::new()
        .with_title(title)
        .build(&event_loop)
        .unwrap();
    use futures::executor::block_on;
    let mut state = block_on(State::new(&window)); // NEW!
    let mut last_render_time = std::time::Instant::now();
    event_loop.run(move |event, _, control_flow| {
        *control_flow = ControlFlow::Poll;
        match event {
            Event::MainEventsCleared => window.request_redraw(),
            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, .. } => {
                            state.resize(**new_inner_size);
                        }
                        _ => {}
                    }
                }
            }
            Event::RedrawRequested(_) => {
                let now = std::time::Instant::now();
                let dt = now - last_render_time;
                last_render_time = now;
                state.update(dt);
                state.render();
            }
            _ => {}
        }
    });
}
