use super::raster::Dem;
use {
    bytemuck::{Pod, Zeroable},
    std::{borrow::Cow, 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,
    uniforms: Uniforms,
    animation_start: std::time::Instant,
}

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

struct Uniforms {
    projection_matrix: glam::Mat4,
    view_matrix: glam::Mat4,
    buffer: wgpu::Buffer,
}

impl Uniforms {
    fn new(device: &wgpu::Device, aspect_ratio: f32) -> Self {
        let projection_matrix =
            glam::Mat4::perspective_rh(std::f32::consts::FRAC_PI_4, aspect_ratio, 1.0, 10.0);
        let view_matrix = glam::Mat4::look_at_rh(glam::Vec3::ZERO, glam::Vec3::ZERO, glam::Vec3::Z);
        let camera_matrix = projection_matrix * view_matrix;
        let camera_matrix_ref: &[f32; 16] = camera_matrix.as_ref();
        let buffer = device.create_buffer_init(&wgpu::util::BufferInitDescriptor {
            label: Some("Uniform Buffer"),
            contents: bytemuck::cast_slice(camera_matrix_ref),
            usage: wgpu::BufferUsages::UNIFORM | wgpu::BufferUsages::COPY_DST,
        });
        Self {
            projection_matrix,
            view_matrix,
            buffer,
        }
    }

    fn set_camera_position(&mut self, position: glam::Vec3) {
        self.view_matrix = glam::Mat4::look_at_rh(position, glam::Vec3::ZERO, 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 update_buffer(&self, queue: &wgpu::Queue) {
        let camera_matrix = self.projection_matrix * self.view_matrix;
        let camera_matrix_ref: &[f32; 16] = camera_matrix.as_ref();
        queue.write_buffer(&self.buffer, 0, bytemuck::cast_slice(camera_matrix_ref))
    }

    fn binding(&self) -> wgpu::BindingResource<'_> {
        self.buffer.as_entire_binding()
    }
}

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

        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 uniforms = Uniforms::new(
            device,
            surface_config.width as f32 / surface_config.height as f32,
        );

        let bind_group_layout = device.create_bind_group_layout(&wgpu::BindGroupLayoutDescriptor {
            label: None,
            entries: &[
                wgpu::BindGroupLayoutEntry {
                    binding: 0,
                    visibility: wgpu::ShaderStages::VERTEX,
                    ty: wgpu::BindingType::Buffer {
                        ty: wgpu::BufferBindingType::Uniform,
                        has_dynamic_offset: false,
                        min_binding_size: wgpu::BufferSize::new(64),
                    },
                    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.binding(),
            }],
            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(),
            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.uniforms
            .set_camera_position(get_animated_camera_position(self.animation_start.elapsed()));
        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 vertex(pos: [i8; 3]) -> Vertex {
    Vertex {
        position: [pos[0] as f32, pos[1] as f32, pos[2] as f32, 1.0],
    }
}

fn create_vertices() -> (Vec<Vertex>, Vec<u16>) {
    let vertex_data = [
        // top (0, 0, 1)
        vertex([-1, -1, 1]),
        vertex([1, -1, 1]),
        vertex([1, 1, 1]),
        vertex([-1, 1, 1]),
        // bottom (0, 0, -1)
        vertex([-1, 1, -1]),
        vertex([1, 1, -1]),
        vertex([1, -1, -1]),
        vertex([-1, -1, -1]),
        // right (1, 0, 0)
        vertex([1, -1, -1]),
        vertex([1, 1, -1]),
        vertex([1, 1, 1]),
        vertex([1, -1, 1]),
        // left (-1, 0, 0)
        vertex([-1, -1, 1]),
        vertex([-1, 1, 1]),
        vertex([-1, 1, -1]),
        vertex([-1, -1, -1]),
        // front (0, 1, 0)
        vertex([1, 1, -1]),
        vertex([-1, 1, -1]),
        vertex([-1, 1, 1]),
        vertex([1, 1, 1]),
        // back (0, -1, 0)
        vertex([1, -1, 1]),
        vertex([-1, -1, 1]),
        vertex([-1, -1, -1]),
        vertex([1, -1, -1]),
    ];

    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 get_animated_camera_position(animation_time: std::time::Duration) -> glam::Vec3 {
    let animation_phase = 2.0 * std::f32::consts::PI * (animation_time.as_secs_f32() % 10.0) / 10.0;
    glam::Vec3::new(
        5.0 * f32::sin(animation_phase),
        5.0 * f32::cos(animation_phase),
        3.0,
    )
}