use iced_wgpu::wgpu;
use iced_winit::Color;

pub struct Scene {
    pub background_color: Color,
    pipeline: wgpu::RenderPipeline,
    bind_group: wgpu::BindGroup,
}

impl Scene {
    pub fn new(device: &wgpu::Device) -> Scene {
        let (pipeline, bind_group) = build_pipeline(device);

        Scene {
            background_color: Color::BLACK,
            pipeline,
            bind_group,
        }
    }

    pub fn draw(
        &self,
        encoder: &mut wgpu::CommandEncoder,
        target: &wgpu::TextureView,
    ) {
        let mut rpass =
            encoder.begin_render_pass(&wgpu::RenderPassDescriptor {
                color_attachments: &[
                    wgpu::RenderPassColorAttachmentDescriptor {
                        attachment: target,
                        resolve_target: None,
                        load_op: wgpu::LoadOp::Clear,
                        store_op: wgpu::StoreOp::Store,
                        clear_color: {
                            let [r, g, b, a] =
                                self.background_color.into_linear();

                            wgpu::Color {
                                r: r as f64,
                                g: g as f64,
                                b: b as f64,
                                a: a as f64,
                            }
                        },
                    },
                ],
                depth_stencil_attachment: None,
            });

        rpass.set_pipeline(&self.pipeline);
        rpass.set_bind_group(0, &self.bind_group, &[]);
        rpass.draw(0..3, 0..1);
    }
}

fn build_pipeline(
    device: &wgpu::Device,
) -> (wgpu::RenderPipeline, wgpu::BindGroup) {
    let vs = include_bytes!("shader/vert.spv");
    let fs = include_bytes!("shader/frag.spv");

    let vs_module = device.create_shader_module(
        &wgpu::read_spirv(std::io::Cursor::new(&vs[..])).unwrap(),
    );

    let fs_module = device.create_shader_module(
        &wgpu::read_spirv(std::io::Cursor::new(&fs[..])).unwrap(),
    );

    let bind_group_layout =
        device.create_bind_group_layout(&wgpu::BindGroupLayoutDescriptor {
            label: None,
            bindings: &[],
        });

    let bind_group = device.create_bind_group(&wgpu::BindGroupDescriptor {
        label: None,
        layout: &bind_group_layout,
        bindings: &[],
    });

    let pipeline_layout =
        device.create_pipeline_layout(&wgpu::PipelineLayoutDescriptor {
            bind_group_layouts: &[&bind_group_layout],
        });

    let pipeline =
        device.create_render_pipeline(&wgpu::RenderPipelineDescriptor {
            layout: &pipeline_layout,
            vertex_stage: wgpu::ProgrammableStageDescriptor {
                module: &vs_module,
                entry_point: "main",
            },
            fragment_stage: Some(wgpu::ProgrammableStageDescriptor {
                module: &fs_module,
                entry_point: "main",
            }),
            rasterization_state: Some(wgpu::RasterizationStateDescriptor {
                front_face: wgpu::FrontFace::Ccw,
                cull_mode: wgpu::CullMode::None,
                depth_bias: 0,
                depth_bias_slope_scale: 0.0,
                depth_bias_clamp: 0.0,
            }),
            primitive_topology: wgpu::PrimitiveTopology::TriangleList,
            color_states: &[wgpu::ColorStateDescriptor {
                format: wgpu::TextureFormat::Bgra8UnormSrgb,
                color_blend: wgpu::BlendDescriptor::REPLACE,
                alpha_blend: wgpu::BlendDescriptor::REPLACE,
                write_mask: wgpu::ColorWrite::ALL,
            }],
            depth_stencil_state: None,
            vertex_state: wgpu::VertexStateDescriptor {
                index_format: wgpu::IndexFormat::Uint16,
                vertex_buffers: &[],
            },
            sample_count: 1,
            sample_mask: !0,
            alpha_to_coverage_enabled: false,
        });

    (pipeline, bind_group)
}