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

pub struct Scene {
    pipeline: wgpu::RenderPipeline,
}

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

        Scene { pipeline }
    }

    pub fn clear<'a>(
        &self,
        target: &'a wgpu::TextureView,
        encoder: &'a mut wgpu::CommandEncoder,
        background_color: Color,
    ) -> wgpu::RenderPass<'a> {
        encoder.begin_render_pass(&wgpu::RenderPassDescriptor {
            color_attachments: &[wgpu::RenderPassColorAttachmentDescriptor {
                attachment: target,
                resolve_target: None,
                ops: wgpu::Operations {
                    load: wgpu::LoadOp::Clear({
                        let [r, g, b, a] = background_color.into_linear();

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

    pub fn draw<'a>(&'a self, render_pass: &mut wgpu::RenderPass<'a>) {
        render_pass.set_pipeline(&self.pipeline);
        render_pass.draw(0..3, 0..1);
    }
}

fn build_pipeline(device: &wgpu::Device) -> wgpu::RenderPipeline {
    let vs_module =
        device.create_shader_module(wgpu::include_spirv!("shader/vert.spv"));

    let fs_module =
        device.create_shader_module(wgpu::include_spirv!("shader/frag.spv"));

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

    let pipeline =
        device.create_render_pipeline(&wgpu::RenderPipelineDescriptor {
            label: None,
            layout: Some(&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,
                ..Default::default()
            }),
            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
}