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

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

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

        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 {
            label: None,
            color_attachments: &[Some(wgpu::RenderPassColorAttachment {
                view: 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,
    texture_format: wgpu::TextureFormat,
) -> wgpu::RenderPipeline {
    let (vs_module, fs_module) = (
        device.create_shader_module(wgpu::include_wgsl!("shader/vert.wgsl")),
        device.create_shader_module(wgpu::include_wgsl!("shader/frag.wgsl")),
    );

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

    device.create_render_pipeline(&wgpu::RenderPipelineDescriptor {
        label: None,
        layout: Some(&pipeline_layout),
        vertex: wgpu::VertexState {
            module: &vs_module,
            entry_point: "main",
            buffers: &[],
        },
        fragment: Some(wgpu::FragmentState {
            module: &fs_module,
            entry_point: "main",
            targets: &[Some(wgpu::ColorTargetState {
                format: texture_format,
                blend: Some(wgpu::BlendState {
                    color: wgpu::BlendComponent::REPLACE,
                    alpha: wgpu::BlendComponent::REPLACE,
                }),
                write_mask: wgpu::ColorWrites::ALL,
            })],
        }),
        primitive: wgpu::PrimitiveState {
            topology: wgpu::PrimitiveTopology::TriangleList,
            front_face: wgpu::FrontFace::Ccw,
            ..Default::default()
        },
        depth_stencil: None,
        multisample: wgpu::MultisampleState {
            count: 1,
            mask: !0,
            alpha_to_coverage_enabled: false,
        },
        multiview: None,
    })
}
