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

#[cfg(target_arch = "wasm32")]
use wasm_bindgen::prelude::*;

mod camera;
mod model;
mod resources;
mod texture;

mod render;

use model::{DrawLight, DrawModel};

const NUM_INSTANCES_PER_ROW: u32 = 10;

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

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

    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(),
            normal: cgmath::Matrix3::from(self.rotation).into(),
        }
    }
}

#[repr(C)]
#[derive(Debug, Copy, Clone, bytemuck::Pod, bytemuck::Zeroable)]
#[allow(dead_code)]
struct InstanceRaw {
    model: [[f32; 4]; 4],
    normal: [[f32; 3]; 3],
}

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::VertexStepMode::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,
                },
                wgpu::VertexAttribute {
                    offset: mem::size_of::<[f32; 16]>() as wgpu::BufferAddress,
                    shader_location: 9,
                    format: wgpu::VertexFormat::Float32x3,
                },
                wgpu::VertexAttribute {
                    offset: mem::size_of::<[f32; 19]>() as wgpu::BufferAddress,
                    shader_location: 10,
                    format: wgpu::VertexFormat::Float32x3,
                },
                wgpu::VertexAttribute {
                    offset: mem::size_of::<[f32; 22]>() as wgpu::BufferAddress,
                    shader_location: 11,
                    format: wgpu::VertexFormat::Float32x3,
                },
            ],
        }
    }
}

#[repr(C)]
#[derive(Debug, Copy, Clone, bytemuck::Pod, bytemuck::Zeroable)]
struct LightUniform {
    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],
    _padding2: u32,
}

struct State {
    surface: wgpu::Surface,
    device: wgpu::Device,
    queue: wgpu::Queue,
    config: wgpu::SurfaceConfiguration,
    obj_model: model::Model,
    camera: camera::Camera,
    projection: camera::Projection,
    camera_controller: camera::CameraController,
    camera_uniform: CameraUniform,
    camera_buffer: wgpu::Buffer,
    camera_bind_group: wgpu::BindGroup,
    instances: Vec<Instance>,
    #[allow(dead_code)]
    instance_buffer: wgpu::Buffer,
    depth_texture: texture::Texture,
    size: winit::dpi::PhysicalSize<u32>,
    light_uniform: LightUniform,
    light_buffer: wgpu::Buffer,
    light_bind_group: wgpu::BindGroup,
    #[allow(dead_code)]
    debug_material: model::Material,
    mouse_pressed: bool,
    pipelines: render::Pipelines
}

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::Backends::all());
        let surface = unsafe { instance.create_surface(window) };
        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 config = wgpu::SurfaceConfiguration {
            usage: wgpu::TextureUsages::RENDER_ATTACHMENT,
            format: surface.get_preferred_format(&adapter).unwrap(),
            width: size.width,
            height: size.height,
            present_mode: wgpu::PresentMode::Fifo,
        };

        surface.configure(&device, &config);

        let global_bind_layout = render::GlobalBindLayout::new(&device);
        let pipelines = render::Pipelines::new(&global_bind_layout, &device, &config);

        // 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(config.width, config.height, cgmath::Deg(45.0), 0.1, 100.0);
        let camera_controller = camera::CameraController::new(4.0, 0.4);

        let mut camera_uniform = CameraUniform::new();
        camera_uniform.update_view_proj(&camera, &projection);

        let camera_buffer = device.create_buffer_init(&wgpu::util::BufferInitDescriptor {
            label: Some("Camera Buffer"),
            contents: bytemuck::cast_slice(&[camera_uniform]),
            usage: wgpu::BufferUsages::UNIFORM | wgpu::BufferUsages::COPY_DST,
        });

        const SPACE_BETWEEN: f32 = 3.0;
        let iter = {
            cfg_if::cfg_if! {
                if #[cfg(target_arch = "wasm32")] {
                    (0..NUM_INSTANCES_PER_ROW)
                    .into_iter()
                } else {
                    (0..NUM_INSTANCES_PER_ROW)
                    .into_par_iter()
                }
            }
        };
        let instances = iter
            .clone()
            .flat_map(|z| {
                // UPDATED!
                iter.clone().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.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::BufferUsages::VERTEX,
        });

        let camera_bind_group = device.create_bind_group(&wgpu::BindGroupDescriptor {
            layout: global_bind_layout.get_camera_bind_layout(),
            entries: &[wgpu::BindGroupEntry {
                binding: 0,
                resource: camera_buffer.as_entire_binding(),
            }],
            label: Some("camera_bind_group"),
        });

        let obj_model =
            resources::load_model("cube.obj", &device, &queue, global_bind_layout.get_texture_bind_layout())
                .await
                .unwrap();

        let light_uniform = LightUniform {
            position: [2.0, 2.0, 2.0],
            _padding: 0,
            color: [1.0, 1.0, 1.0],
            _padding2: 0,
        };

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

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

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

        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,
                global_bind_layout.get_texture_bind_layout(),
            )
        };

        Self {
            surface,
            device,
            queue,
            config,
            obj_model,
            camera,
            projection,
            camera_controller,
            camera_buffer,
            camera_bind_group,
            camera_uniform,
            instances,
            instance_buffer,
            depth_texture,
            size,
            light_uniform,
            light_buffer,
            light_bind_group,
            #[allow(dead_code)]
            debug_material,
            mouse_pressed: false,
            pipelines
        }
    }

    fn resize(&mut self, new_size: winit::dpi::PhysicalSize<u32>) {
        if new_size.width > 0 && new_size.height > 0 {
            self.projection.resize(new_size.width, new_size.height);
            self.size = new_size;
            self.config.width = new_size.width;
            self.config.height = new_size.height;
            self.surface.configure(&self.device, &self.config);
            self.depth_texture =
                texture::Texture::create_depth_texture(&self.device, &self.config, "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
            }
            _ => false,
        }
    }

    fn update(&mut self, dt: instant::Duration) {
        self.camera_controller.update_camera(&mut self.camera, dt);
        self.camera_uniform
            .update_view_proj(&self.camera, &self.projection);
        self.queue.write_buffer(
            &self.camera_buffer,
            0,
            bytemuck::cast_slice(&[self.camera_uniform]),
        );

        // Update the light
        let old_position: cgmath::Vector3<_> = self.light_uniform.position.into();
        self.light_uniform.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_uniform]),
        );
    }

    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: &[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: 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.pipelines.get_light_pipeline());
            render_pass.draw_light_model(
                &self.obj_model,
                &self.camera_bind_group,
                &self.light_bind_group,
            );

            render_pass.set_pipeline(self.pipelines.get_render_pipeline());
            render_pass.draw_model_instanced(
                &self.obj_model,
                0..self.instances.len() as u32,
                &self.camera_bind_group,
                &self.light_bind_group,
            );
        }
        self.queue.submit(iter::once(encoder.finish()));
        output.present();

        Ok(())
    }
}

#[cfg_attr(target_arch = "wasm32", wasm_bindgen(start))]
pub async fn run() {
    cfg_if::cfg_if! {
        if #[cfg(target_arch = "wasm32")] {
            std::panic::set_hook(Box::new(console_error_panic_hook::hook));
            console_log::init_with_level(log::Level::Info).expect("Could't initialize logger");
        } else {
            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();

    #[cfg(target_arch = "wasm32")]
    {
        // Winit prevents sizing with CSS, so we have to set
        // the size manually when on web.
        use winit::dpi::PhysicalSize;
        window.set_inner_size(PhysicalSize::new(450, 400));

        use winit::platform::web::WindowExtWebSys;
        web_sys::window()
            .and_then(|win| win.document())
            .and_then(|doc| {
                let dst = doc.get_element_by_id("wasm-example")?;
                let canvas = web_sys::Element::from(window.canvas());
                dst.append_child(&canvas).ok()?;
                Some(())
            })
            .expect("Couldn't append canvas to document body.");
    }

    let mut state = State::new(&window).await; // NEW!
    let mut last_render_time = instant::Instant::now();
    event_loop.run(move |event, _, control_flow| {
        *control_flow = ControlFlow::Poll;
        match event {
            Event::MainEventsCleared => window.request_redraw(),
            // NEW!
            Event::DeviceEvent {
                event: DeviceEvent::MouseMotion{ delta, },
                .. // We're not using device_id currently
            } => if state.mouse_pressed {
                state.camera_controller.process_mouse(delta.0, delta.1)
            }
            // UPDATED!
            Event::WindowEvent {
                ref event,
                window_id,
            } if window_id == window.id() && !state.input(event) => {
                match event {
                    #[cfg(not(target_arch="wasm32"))]
                    WindowEvent::CloseRequested
                    | WindowEvent::KeyboardInput {
                        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(window_id) if window_id == window.id() => {
                let now = instant::Instant::now();
                let dt = now - last_render_time;
                last_render_time = now;
                state.update(dt);
                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) => *control_flow = ControlFlow::Exit,
                    // We're ignoring timeouts
                    Err(wgpu::SurfaceError::Timeout) => log::warn!("Surface timeout"),
                }
            }
            _ => {}
        }
    });
}
