use super::*;
use crate::viewport::ViewportInfo;
use crate::RenderLayouts;

#[repr(C)]
#[derive(Copy, Clone, bytemuck::Pod, bytemuck::Zeroable)]
pub struct Vertex {
    pub position: [f32; 3],
    pub color: [f32; 3],
}

const VERTEX_ATTRS: &[wgpu::VertexAttribute] =
    &wgpu::vertex_attr_array![0 => Float32x3, 1 => Float32x3];

impl Vertex {
    pub fn desc() -> wgpu::VertexBufferLayout<'static> {
        wgpu::VertexBufferLayout {
            array_stride: std::mem::size_of::<Self>() as wgpu::BufferAddress,
            step_mode: wgpu::VertexStepMode::Vertex,
            attributes: VERTEX_ATTRS,
        }
    }
}

pub type Index = u32;

pub struct FrameData {
    vertex_capacity: usize,
    vertices: wgpu::Buffer,
    index_capacity: usize,
    indices: wgpu::Buffer,
    index_num: usize,
}

pub struct DebugPass {
    device: Arc<wgpu::Device>,
    pipeline: wgpu::RenderPipeline,
    target_info: ViewportInfo,
}

impl DebugPass {
    pub fn new(
        device: Arc<wgpu::Device>,
        layouts: Arc<RenderLayouts>,
        target_info: ViewportInfo,
    ) -> Self {
        // TODO hook into ShaderStore system
        let shader = device.create_shader_module(&wgpu::include_wgsl!("debug_shader.wgsl"));

        let pipeline_layout = device.create_pipeline_layout(&wgpu::PipelineLayoutDescriptor {
            label: Some("DebugPass Pipeline Layout"),
            bind_group_layouts: &[&layouts.bind_viewport],
            push_constant_ranges: &[],
        });

        let pipeline = device.create_render_pipeline(&wgpu::RenderPipelineDescriptor {
            label: Some("DebugPass Pipeline"),
            layout: Some(&pipeline_layout),
            vertex: wgpu::VertexState {
                module: &shader,
                entry_point: "vs_main",
                buffers: &[Vertex::desc()],
            },
            fragment: Some(wgpu::FragmentState {
                module: &shader,
                entry_point: "fs_main",
                targets: &[wgpu::ColorTargetState {
                    format: target_info.output_format,
                    blend: Some(wgpu::BlendState::REPLACE),
                    write_mask: wgpu::ColorWrites::ALL,
                }],
            }),
            primitive: wgpu::PrimitiveState {
                topology: wgpu::PrimitiveTopology::LineList,
                strip_index_format: None,
                front_face: wgpu::FrontFace::Ccw,
                cull_mode: None,
                polygon_mode: wgpu::PolygonMode::Fill,
                unclipped_depth: false,
                conservative: false,
            },
            depth_stencil: Some(wgpu::DepthStencilState {
                format: target_info.depth_format,
                depth_write_enabled: false,
                depth_compare: wgpu::CompareFunction::Less,
                stencil: Default::default(),
                bias: Default::default(),
            }),
            multisample: wgpu::MultisampleState {
                count: 1,
                mask: !0,
                alpha_to_coverage_enabled: false,
            },
            multiview: None,
        });

        Self {
            device,
            pipeline,
            target_info,
        }
    }
}

impl RenderPass for DebugPass {
    type FrameData = FrameData;

    fn create_frame_data(&self) -> FrameData {
        let vertex_capacity = 1024 * 1024; // TODO resizable buffers
        let vertices = self.device.create_buffer(&wgpu::BufferDescriptor {
            label: Some("DebugPass Vertex Buffer"),
            size: (vertex_capacity * std::mem::size_of::<Vertex>()) as wgpu::BufferAddress,
            mapped_at_creation: false,
            usage: wgpu::BufferUsages::VERTEX | wgpu::BufferUsages::COPY_DST,
        });

        let index_capacity = 1024 * 1024; // TODO resizable buffers
        let indices = self.device.create_buffer(&wgpu::BufferDescriptor {
            label: Some("DebugPass Index Buffer"),
            size: (index_capacity * std::mem::size_of::<Index>()) as wgpu::BufferAddress,
            mapped_at_creation: false,
            usage: wgpu::BufferUsages::INDEX | wgpu::BufferUsages::COPY_DST,
        });

        let index_num = 0;

        FrameData {
            vertex_capacity,
            vertices,
            index_capacity,
            indices,
            index_num,
        }
    }

    fn begin_frame(&self, data: &mut FrameData, phases: &mut Vec<Phase>, queue: &wgpu::Queue) {
        phases.push(Phase::Overlay);

        let vertices = &[
            Vertex {
                position: [0.0, 0.0, -1.0],
                color: [1.0, 0.0, 0.0],
            },
            Vertex {
                position: [0.0, 0.0, 1.0],
                color: [0.0, 0.0, 1.0],
            },
        ];
        queue.write_buffer(&data.vertices, 0, bytemuck::cast_slice(vertices));

        let indices = &[0u32, 1u32];
        queue.write_buffer(&data.indices, 0, bytemuck::cast_slice(indices));

        data.index_num = 2;
    }

    fn record_render(&self, data: PhaseData<&FrameData>) -> Option<wgpu::RenderBundle> {
        println!("DebugPass::record_render(phase: {:?})", data.phase);

        let mut cmds =
            self.device
                .create_render_bundle_encoder(&wgpu::RenderBundleEncoderDescriptor {
                    label: Some("DebugPass Render Bundle"),
                    color_formats: &[self.target_info.output_format],
                    depth_stencil: Some(wgpu::RenderBundleDepthStencil {
                        format: self.target_info.depth_format,
                        depth_read_only: false, // TODO optimize?
                        stencil_read_only: true,
                    }),
                    sample_count: 1,
                    multiview: None,
                });

        cmds.set_pipeline(&self.pipeline);
        cmds.set_bind_group(0, data.bind_viewport, &[]);
        cmds.set_vertex_buffer(0, data.frame_data.vertices.slice(..));
        cmds.set_index_buffer(data.frame_data.indices.slice(..), wgpu::IndexFormat::Uint32);

        let index_range = 0..(data.frame_data.index_num as u32);
        cmds.draw_indexed(index_range, 0, 0..1);

        Some(cmds.finish(&wgpu::RenderBundleDescriptor::default()))
    }
}