//! State implementations.

pub mod camera;
pub mod instance;
pub mod vertex;

use std::sync::Arc;

use glam::{Quat, Vec3};
use wgpu::util::DeviceExt;
use winit::{event::WindowEvent, event_loop::EventLoop, window::Window};

use crate::texture::Texture;

use camera::{Camera, CameraController, CameraUniform};
use instance::{Instance, InstanceRaw};
use vertex::Vertex;

const VERTICES: &[Vertex] = &[
    Vertex {
        position: [-0.0868241, 0.49240386, 0.0],
        tex_coords: [0.4131759, 0.00759614],
    },
    Vertex {
        position: [-0.49513406, 0.06958647, 0.0],
        tex_coords: [0.0048659444, 0.43041354],
    },
    Vertex {
        position: [-0.21918549, -0.44939706, 0.0],
        tex_coords: [0.28081453, 0.949397],
    },
    Vertex {
        position: [0.35966998, -0.3473291, 0.0],
        tex_coords: [0.85967, 0.84732914],
    },
    Vertex {
        position: [0.44147372, 0.2347359, 0.0],
        tex_coords: [0.9414737, 0.2652641],
    },
];

const INDICES: &[u16] = &[0, 1, 4, 1, 2, 4, 2, 3, 4];
const NUM_INSTANCES_PER_ROW: u32 = 1000;
const INSTANCE_DISPLACEMENT: Vec3 = Vec3::new(
    NUM_INSTANCES_PER_ROW as f32 * 0.5,
    0.0,
    NUM_INSTANCES_PER_ROW as f32 * 0.5,
);

#[derive(Debug)]
pub struct State<'s> {
    pub window: Arc<Window>,
    pub size: winit::dpi::PhysicalSize<u32>,

    surface: wgpu::Surface<'s>,
    device: wgpu::Device,
    queue: wgpu::Queue,
    config: wgpu::SurfaceConfiguration,
    render_pipeline: wgpu::RenderPipeline,
    vertex_buffer: wgpu::Buffer,
    index_buffer: wgpu::Buffer,
    diffuse_bind_group: wgpu::BindGroup,
    diffuse_texture: Texture,
    camera: Camera,
    camera_uniform: CameraUniform,
    camera_buffer: wgpu::Buffer,
    camera_bind_group: wgpu::BindGroup,
    camera_controller: CameraController,
    instances: Vec<Instance>,
    instance_buffer: wgpu::Buffer,
    depth_texture: Texture,
}

impl<'s> State<'s> {
    pub async fn new(event_loop: &EventLoop<()>) -> State<'s> {
        let window = Arc::new(Window::new(event_loop).unwrap());
        let size = window.inner_size();

        let instance = wgpu::Instance::new(wgpu::InstanceDescriptor {
            backends: wgpu::Backends::all(),
            ..Default::default()
        });

        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
            .unwrap();

        let (device, queue) = adapter
            .request_device(
                &wgpu::DeviceDescriptor {
                    required_features: wgpu::Features::empty(),
                    required_limits: wgpu::Limits::default(),
                    label: None,
                },
                None,
            )
            .await
            .unwrap();

        let caps = surface.get_capabilities(&adapter);
        let config = wgpu::SurfaceConfiguration {
            usage: wgpu::TextureUsages::RENDER_ATTACHMENT,
            format: caps.formats[0],
            width: size.width,
            height: size.height,
            present_mode: wgpu::PresentMode::Fifo,
            alpha_mode: Default::default(),
            view_formats: vec![],
            desired_maximum_frame_latency: 0,
        };
        surface.configure(&device, &config);

        let diffuse_bytes = include_bytes!("../happy-tree.png");
        let diffuse_texture =
            Texture::from_bytes(&device, &queue, diffuse_bytes, "happy-tree.png").unwrap();

        let texture_bind_group_layout =
            device.create_bind_group_layout(&wgpu::BindGroupLayoutDescriptor {
                entries: &[
                    wgpu::BindGroupLayoutEntry {
                        binding: 0,
                        visibility: wgpu::ShaderStages::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::ShaderStages::FRAGMENT,
                        ty: wgpu::BindingType::Sampler(wgpu::SamplerBindingType::Filtering),
                        count: None,
                    },
                ],
                label: Some("texture_bind_group_layout"),
            });
        let diffuse_bind_group = device.create_bind_group(&wgpu::BindGroupDescriptor {
            layout: &texture_bind_group_layout,
            entries: &[
                wgpu::BindGroupEntry {
                    binding: 0,
                    resource: wgpu::BindingResource::TextureView(&diffuse_texture.view),
                },
                wgpu::BindGroupEntry {
                    binding: 1,
                    resource: wgpu::BindingResource::Sampler(&diffuse_texture.sampler),
                },
            ],
            label: Some("diffuse_bind_group"),
        });

        let camera = Camera {
            eye: (0.0, 1.0, 2.0).into(),
            direction: Vec3::X,
            aspect: config.width as f32 / config.height as f32,
            fov_y: 45.0,
            z_near: 0.1,
            z_far: 100.0,
        };

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

        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,
        });
        let camera_bind_group_layout =
            device.create_bind_group_layout(&wgpu::BindGroupLayoutDescriptor {
                entries: &[wgpu::BindGroupLayoutEntry {
                    binding: 0,
                    visibility: wgpu::ShaderStages::VERTEX,
                    ty: wgpu::BindingType::Buffer {
                        ty: wgpu::BufferBindingType::Uniform,
                        has_dynamic_offset: false,
                        min_binding_size: None,
                    },
                    count: None,
                }],
                label: Some("camera_bind_group_layout"),
            });
        let camera_bind_group = device.create_bind_group(&wgpu::BindGroupDescriptor {
            layout: &camera_bind_group_layout,
            entries: &[wgpu::BindGroupEntry {
                binding: 0,
                resource: camera_buffer.as_entire_binding(),
            }],
            label: Some("camera_bind_group"),
        });

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

        let shader = device.create_shader_module(wgpu::include_wgsl!("../shader.wgsl"));
        let render_pipeline_layout =
            device.create_pipeline_layout(&wgpu::PipelineLayoutDescriptor {
                label: Some("Render Pipeline Layout"),
                bind_group_layouts: &[&texture_bind_group_layout, &camera_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: "vs_main",
                buffers: &[Vertex::desc(), InstanceRaw::desc()],
            },
            fragment: Some(wgpu::FragmentState {
                module: &shader,
                entry_point: "fs_main",
                targets: &[Some(wgpu::ColorTargetState {
                    format: config.format,
                    blend: Some(wgpu::BlendState::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),
                polygon_mode: wgpu::PolygonMode::Fill,
                unclipped_depth: false,
                conservative: false,
            },
            depth_stencil: Some(wgpu::DepthStencilState {
                format: Texture::DEPTH_FORMAT,
                depth_write_enabled: true,
                depth_compare: wgpu::CompareFunction::Less,
                stencil: wgpu::StencilState::default(),
                bias: wgpu::DepthBiasState::default(),
            }),
            multisample: wgpu::MultisampleState {
                count: 1,
                mask: !0,
                alpha_to_coverage_enabled: false,
            },
            multiview: None,
        });

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

        let camera_controller = CameraController::new(0.2);

        let instances = (0..NUM_INSTANCES_PER_ROW)
            .flat_map(|z| {
                (0..NUM_INSTANCES_PER_ROW).map(move |x| {
                    let position = Vec3 {
                        x: x as f32,
                        y: 0.0,
                        z: z as f32,
                    } - INSTANCE_DISPLACEMENT;

                    let rotation = if position.length().abs() <= std::f32::EPSILON {
                        Quat::from_axis_angle(Vec3::Z, 0.0)
                    } else {
                        Quat::from_axis_angle(position.normalize(), std::f32::consts::FRAC_PI_4)
                    };

                    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,
        });

        Self {
            window,
            size,
            surface,
            device,
            queue,
            config,
            render_pipeline,
            vertex_buffer,
            index_buffer,
            diffuse_bind_group,
            diffuse_texture,
            camera,
            camera_uniform,
            camera_buffer,
            camera_bind_group,
            camera_controller,
            instances,
            instance_buffer,
            depth_texture,
        }
    }
}

impl<'s> State<'s> {
    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);
        }
        self.depth_texture =
            Texture::create_depth_texture(&self.device, &self.config, "depth_texture");
    }

    pub fn update(&mut self) {
        self.camera_controller.update_camera(&mut self.camera);
        self.camera_uniform.update_view_or_orthographic_proj(self.camera_controller.is_orthographic(), &self.camera);
        self.queue.write_buffer(
            &self.camera_buffer,
            0,
            bytemuck::cast_slice(&[self.camera_uniform]),
        );
    }

    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: 1.0,
                            g: 0.2,
                            b: 0.9,
                            a: 1.0,
                        }),
                        store: wgpu::StoreOp::Store,
                    },
                })],
                depth_stencil_attachment: Some(wgpu::RenderPassDepthStencilAttachment {
                    view: &self.depth_texture.view,
                    depth_ops: Some(wgpu::Operations {
                        load: wgpu::LoadOp::Clear(1.0),
                        store: wgpu::StoreOp::Store,
                    }),
                    stencil_ops: None,
                }),
                ..Default::default()
            });

            render_pass.set_pipeline(&self.render_pipeline);
            render_pass.set_bind_group(0, &self.diffuse_bind_group, &[]);
            render_pass.set_bind_group(1, &self.camera_bind_group, &[]);
            render_pass.set_vertex_buffer(0, self.vertex_buffer.slice(..));
            render_pass.set_vertex_buffer(1, self.instance_buffer.slice(..));
            render_pass.set_index_buffer(self.index_buffer.slice(..), wgpu::IndexFormat::Uint16);

            render_pass.draw_indexed(0..INDICES.len() as _, 0, 0..self.instances.len() as _);
        }

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

        Ok(())
    }

    pub fn input(&mut self, event: &WindowEvent) -> bool {
        self.camera_controller.process_events(event)
    }
}
