use super::raster::Dem;
use {
    bytemuck::{Pod, Zeroable},
    std::{borrow::Cow, num::NonZero, rc::Rc},
    wgpu::util::DeviceExt,
};

pub struct DemRenderer {
    source: Rc<Dem>,
    pipeline: wgpu::RenderPipeline,
    bind_group: wgpu::BindGroup,
    vertex_buffer: wgpu::Buffer,
    index_buffer: wgpu::Buffer,
    index_count: usize,
    camera: Camera,
    uniforms: UniformBufferManager,
    animation_start: std::time::Instant,
}

#[repr(C)]
#[derive(Clone, Copy, Pod, Zeroable)]
struct Vertex {
    position: [f32; 4],
}

impl Vertex {
    fn new(x: f32, y: f32, z: f32) -> Self {
        Self {
            position: [x, y, z, 1.0],
        }
    }
}

struct Camera {
    projection_matrix: glam::Mat4,
    view_matrix: glam::Mat4,
}

impl Camera {
    fn new(viewport_aspect_ratio: f32) -> Self {
        let projection_matrix = glam::Mat4::perspective_rh(
            std::f32::consts::FRAC_PI_4,
            viewport_aspect_ratio,
            1.0,
            10000.0,
        );
        let view_matrix = glam::Mat4::look_at_rh(glam::Vec3::ZERO, glam::Vec3::ZERO, glam::Vec3::Z);
        Self {
            projection_matrix,
            view_matrix,
        }
    }

    fn set_position(&mut self, camera_position: glam::Vec3, camera_look_at: glam::Vec3) {
        self.view_matrix = glam::Mat4::look_at_rh(camera_position, camera_look_at, glam::Vec3::Z);
    }

    fn set_aspect_ratio(&mut self, ratio: f32) {
        self.projection_matrix =
            glam::Mat4::perspective_rh(std::f32::consts::FRAC_PI_4, ratio, 1.0, 10.0);
    }

    fn get_matrix(&self) -> glam::Mat4 {
        self.projection_matrix * self.view_matrix
    }
}

#[repr(C)]
#[derive(Clone, Copy, Pod, Zeroable)]
struct UniformBufferContents {
    camera_matrix: [f32; 16],
    dem_texture_size: [u32; 2],
}
// This struct is 72 bytes but WGSL expects the buffer size to be be a multiple
// of the alignment of the member with the largest alignment. The mat4x4<f32>
// type has a 16-byte alignment, so we round up to 16 * 5 = 80.
const UNIFORM_BUFFER_SIZE: u64 = 80;

struct UniformBufferManager {
    cpu_buffer: UniformBufferContents,
    gpu_buffer: wgpu::Buffer,
}

impl UniformBufferManager {
    fn new(device: &wgpu::Device) -> Self {
        let cpu_buffer = UniformBufferContents::zeroed();
        let gpu_buffer = device.create_buffer_init(&wgpu::util::BufferInitDescriptor {
            label: Some("Uniform Buffer"),
            contents: &[0u8; UNIFORM_BUFFER_SIZE as usize],
            usage: wgpu::BufferUsages::UNIFORM | wgpu::BufferUsages::COPY_DST,
        });
        Self {
            cpu_buffer,
            gpu_buffer,
        }
    }

    fn set_camera_matrix(&mut self, camera_matrix: glam::Mat4) {
        self.cpu_buffer
            .camera_matrix
            .clone_from_slice(&camera_matrix.to_cols_array())
    }

    fn set_dem_texture_size(&mut self, dem_texture_size: glam::UVec2) {
        self.cpu_buffer
            .dem_texture_size
            .clone_from_slice(&dem_texture_size.to_array());
    }

    fn get_binding(&self) -> wgpu::BindingResource<'_> {
        wgpu::BindingResource::Buffer(wgpu::BufferBinding {
            buffer: &self.gpu_buffer,
            offset: 0,
            size: NonZero::new(UNIFORM_BUFFER_SIZE),
        })
    }

    fn update_buffer(&self, queue: &wgpu::Queue) {
        queue.write_buffer(&self.gpu_buffer, 0, bytemuck::bytes_of(&self.cpu_buffer));
    }
}

impl DemRenderer {
    pub fn new(
        source: Rc<Dem>,
        device: &wgpu::Device,
        surface_config: &wgpu::SurfaceConfiguration,
        queue: &wgpu::Queue,
    ) -> Self {
        let (vertex_data, index_data) = create_vertices(&source);

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

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

        let index_count = index_data.len();

        let (dem_texture_view, dem_texture_size) = load_dem_texture(&source, device, queue);

        let camera = Camera::new(surface_config.width as f32 / surface_config.height as f32);

        let mut uniforms = UniformBufferManager::new(device);
        uniforms.set_dem_texture_size(dem_texture_size);

        let bind_group_layout = device.create_bind_group_layout(&wgpu::BindGroupLayoutDescriptor {
            label: None,
            entries: &[
                wgpu::BindGroupLayoutEntry {
                    binding: 0,
                    visibility: wgpu::ShaderStages::VERTEX | wgpu::ShaderStages::FRAGMENT,
                    ty: wgpu::BindingType::Buffer {
                        ty: wgpu::BufferBindingType::Uniform,
                        has_dynamic_offset: false,
                        min_binding_size: wgpu::BufferSize::new(UNIFORM_BUFFER_SIZE),
                    },
                    count: None,
                },
                wgpu::BindGroupLayoutEntry {
                    binding: 1,
                    visibility: wgpu::ShaderStages::FRAGMENT,
                    ty: wgpu::BindingType::Texture {
                        multisampled: false,
                        sample_type: wgpu::TextureSampleType::Uint,
                        view_dimension: wgpu::TextureViewDimension::D2,
                    },
                    count: None,
                },
            ],
        });

        let bind_group = device.create_bind_group(&wgpu::BindGroupDescriptor {
            layout: &bind_group_layout,
            entries: &[
                wgpu::BindGroupEntry {
                    binding: 0,
                    resource: uniforms.get_binding(),
                },
                wgpu::BindGroupEntry {
                    binding: 1,
                    resource: wgpu::BindingResource::TextureView(&dem_texture_view),
                },
            ],
            label: Some("DemRendererBindGroup"),
        });

        let pipeline_layout = device.create_pipeline_layout(&wgpu::PipelineLayoutDescriptor {
            label: None,
            bind_group_layouts: &[&bind_group_layout],
            push_constant_ranges: &[],
        });

        let vertex_buffers = [wgpu::VertexBufferLayout {
            array_stride: size_of::<Vertex>() as wgpu::BufferAddress,
            step_mode: wgpu::VertexStepMode::Vertex,
            attributes: &[wgpu::VertexAttribute {
                format: wgpu::VertexFormat::Float32x4,
                offset: 0,
                shader_location: 0,
            }],
        }];

        let shader = device.create_shader_module(wgpu::ShaderModuleDescriptor {
            label: None,
            source: wgpu::ShaderSource::Wgsl(Cow::Borrowed(include_str!("dem_renderer.wgsl"))),
        });

        let pipeline = device.create_render_pipeline(&wgpu::RenderPipelineDescriptor {
            label: Some("DemRendererPipeline"),
            layout: Some(&pipeline_layout),
            vertex: wgpu::VertexState {
                module: &shader,
                entry_point: Some("vs_main"),
                compilation_options: Default::default(),
                buffers: &vertex_buffers,
            },
            fragment: Some(wgpu::FragmentState {
                module: &shader,
                entry_point: Some("fs_solid"),
                compilation_options: Default::default(),
                targets: &[Some(surface_config.view_formats[0].into())],
            }),
            primitive: wgpu::PrimitiveState {
                cull_mode: Some(wgpu::Face::Back),
                ..Default::default()
            },
            depth_stencil: None,
            multisample: wgpu::MultisampleState::default(),
            multiview: None,
            cache: None,
        });
        DemRenderer {
            source,
            pipeline,
            bind_group,
            vertex_buffer,
            index_buffer,
            index_count,
            animation_start: std::time::Instant::now(),
            camera,
            uniforms,
        }
    }

    pub fn render(&mut self, view: &wgpu::TextureView, device: &wgpu::Device, queue: &wgpu::Queue) {
        let mut encoder = device.create_command_encoder(&wgpu::CommandEncoderDescriptor {
            label: Some("DemRendererCommandEncoder"),
        });
        self.camera.set_position(
            get_animated_camera_position(
                self.animation_start.elapsed(),
                self.get_max_dem_dimension(),
            ),
            self.get_dem_centre(),
        );
        self.uniforms.set_camera_matrix(self.camera.get_matrix());
        self.uniforms.update_buffer(queue);
        {
            let mut rpass = encoder.begin_render_pass(&wgpu::RenderPassDescriptor {
                label: Some("DemRendererRenderPass"),
                color_attachments: &[Some(wgpu::RenderPassColorAttachment {
                    view,
                    resolve_target: None,
                    ops: wgpu::Operations {
                        load: wgpu::LoadOp::Clear(wgpu::Color::BLACK),
                        store: wgpu::StoreOp::Store,
                    },
                })],
                depth_stencil_attachment: None,
                timestamp_writes: None,
                occlusion_query_set: None,
            });
            rpass.set_pipeline(&self.pipeline);
            rpass.set_bind_group(0, &self.bind_group, &[]);
            rpass.set_index_buffer(self.index_buffer.slice(..), wgpu::IndexFormat::Uint16);
            rpass.set_vertex_buffer(0, self.vertex_buffer.slice(..));
            rpass.draw_indexed(0..self.index_count as u32, 0, 0..1);
        }
        queue.submit(Some(encoder.finish()));
    }

    fn get_max_dem_dimension(&self) -> f32 {
        let dem = &self.source;
        (dem.x_max - dem.x_min)
            .max(dem.y_max - dem.y_min)
            .max(dem.z_max - dem.x_min)
    }

    fn get_dem_centre(&self) -> glam::Vec3 {
        let dem = &self.source;
        let min_corner = glam::Vec3::new(dem.x_min, dem.y_min, dem.z_min);
        let max_corner = glam::Vec3::new(dem.x_max, dem.y_max, dem.z_max);
        min_corner + (max_corner - min_corner) / 2.0
    }
}

fn create_vertices(dem: &Rc<Dem>) -> (Vec<Vertex>, Vec<u16>) {
    let x_min = dem.x_min;
    let x_max = dem.x_max;
    let y_min = dem.y_min;
    let y_max = dem.y_max;
    let z_min = dem.z_min;
    let z_max = dem.z_max;

    let vertex_data = [
        // top (0, 0, 1)
        Vertex::new(x_min, y_min, z_max),
        Vertex::new(x_max, y_min, z_max),
        Vertex::new(x_max, y_max, z_max),
        Vertex::new(x_min, y_max, z_max),
        // bottom (0, 0, -1)
        Vertex::new(x_min, y_max, z_min),
        Vertex::new(x_max, y_max, z_min),
        Vertex::new(x_max, y_min, z_min),
        Vertex::new(x_min, y_min, z_min),
        // right (1, 0, 0)
        Vertex::new(x_max, y_min, z_min),
        Vertex::new(x_max, y_max, z_min),
        Vertex::new(x_max, y_max, z_max),
        Vertex::new(x_max, y_min, z_max),
        // left (-1, 0, 0)
        Vertex::new(x_min, y_min, z_max),
        Vertex::new(x_min, y_max, z_max),
        Vertex::new(x_min, y_max, z_min),
        Vertex::new(x_min, y_min, z_min),
        // front (0, 1, 0)
        Vertex::new(x_max, y_max, z_min),
        Vertex::new(x_min, y_max, z_min),
        Vertex::new(x_min, y_max, z_max),
        Vertex::new(x_max, y_max, z_max),
        // back (0, -1, 0)
        Vertex::new(x_max, y_min, z_max),
        Vertex::new(x_min, y_min, z_max),
        Vertex::new(x_min, y_min, z_min),
        Vertex::new(x_max, y_min, z_min),
    ];

    let index_data: &[u16] = &[
        0, 1, 2, 2, 3, 0, // top
        4, 5, 6, 6, 7, 4, // bottom
        8, 9, 10, 10, 11, 8, // right
        12, 13, 14, 14, 15, 12, // left
        16, 17, 18, 18, 19, 16, // front
        20, 21, 22, 22, 23, 20, // back
    ];

    (vertex_data.to_vec(), index_data.to_vec())
}

fn load_dem_texture(
    source: &Dem,
    device: &wgpu::Device,
    queue: &wgpu::Queue,
) -> (wgpu::TextureView, glam::UVec2) {
    let texture_size = wgpu::Extent3d {
        width: source.num_cells_x,
        height: source.num_cells_y,
        depth_or_array_layers: 1,
    };
    let texture = device.create_texture(&wgpu::TextureDescriptor {
        label: Some("Dem Texture"),
        size: texture_size,
        mip_level_count: 1,
        sample_count: 1,
        dimension: wgpu::TextureDimension::D2,
        format: wgpu::TextureFormat::R16Uint,
        usage: wgpu::TextureUsages::TEXTURE_BINDING | wgpu::TextureUsages::COPY_DST,
        view_formats: &[],
    });

    queue.write_texture(
        wgpu::ImageCopyTexture {
            texture: &texture,
            mip_level: 0,
            origin: wgpu::Origin3d::ZERO,
            aspect: wgpu::TextureAspect::All,
        },
        bytemuck::cast_slice(&source.grid[..]),
        wgpu::ImageDataLayout {
            offset: 0,
            bytes_per_row: Some(std::mem::size_of::<u16>() as u32 * source.num_cells_x),
            rows_per_image: Some(source.num_cells_y),
        },
        texture_size,
    );

    (
        texture.create_view(&wgpu::TextureViewDescriptor::default()),
        glam::UVec2::new(source.num_cells_x, source.num_cells_y),
    )
}

fn get_animated_camera_position(animation_time: std::time::Duration, dem_size: f32) -> glam::Vec3 {
    let animation_phase = 2.0 * std::f32::consts::PI * (animation_time.as_secs_f32() % 10.0) / 10.0;
    glam::Vec3::new(
        dem_size * f32::sin(animation_phase),
        dem_size * f32::cos(animation_phase),
        dem_size * 0.7,
    )
}