use crate::settings;

#[derive(Debug)]
pub struct Blit {
    format: wgpu::TextureFormat,
    pipeline: wgpu::RenderPipeline,
    constants: wgpu::BindGroup,
    texture_layout: wgpu::BindGroupLayout,
    sample_count: u32,
    targets: Option<Targets>,
}

impl Blit {
    pub fn new(
        device: &wgpu::Device,
        format: wgpu::TextureFormat,
        antialiasing: settings::Antialiasing,
    ) -> Blit {
        let sampler = device.create_sampler(&wgpu::SamplerDescriptor {
            address_mode_u: wgpu::AddressMode::ClampToEdge,
            address_mode_v: wgpu::AddressMode::ClampToEdge,
            address_mode_w: wgpu::AddressMode::ClampToEdge,
            mag_filter: wgpu::FilterMode::Linear,
            min_filter: wgpu::FilterMode::Linear,
            mipmap_filter: wgpu::FilterMode::Linear,
            lod_min_clamp: -100.0,
            lod_max_clamp: 100.0,
            compare: wgpu::CompareFunction::Always,
        });

        let constant_layout =
            device.create_bind_group_layout(&wgpu::BindGroupLayoutDescriptor {
                label: None,
                bindings: &[wgpu::BindGroupLayoutEntry {
                    binding: 0,
                    visibility: wgpu::ShaderStage::FRAGMENT,
                    ty: wgpu::BindingType::Sampler { comparison: false },
                }],
            });

        let constant_bind_group =
            device.create_bind_group(&wgpu::BindGroupDescriptor {
                label: None,
                layout: &constant_layout,
                bindings: &[wgpu::Binding {
                    binding: 0,
                    resource: wgpu::BindingResource::Sampler(&sampler),
                }],
            });

        let texture_layout =
            device.create_bind_group_layout(&wgpu::BindGroupLayoutDescriptor {
                label: None,
                bindings: &[wgpu::BindGroupLayoutEntry {
                    binding: 0,
                    visibility: wgpu::ShaderStage::FRAGMENT,
                    ty: wgpu::BindingType::SampledTexture {
                        dimension: wgpu::TextureViewDimension::D2,
                        component_type: wgpu::TextureComponentType::Float,
                        multisampled: false,
                    },
                }],
            });

        let layout =
            device.create_pipeline_layout(&wgpu::PipelineLayoutDescriptor {
                bind_group_layouts: &[&constant_layout, &texture_layout],
            });

        let vs = include_bytes!("../shader/blit.vert.spv");
        let vs_module = device.create_shader_module(
            &wgpu::read_spirv(std::io::Cursor::new(&vs[..]))
                .expect("Read blit vertex shader as SPIR-V"),
        );

        let fs = include_bytes!("../shader/blit.frag.spv");
        let fs_module = device.create_shader_module(
            &wgpu::read_spirv(std::io::Cursor::new(&fs[..]))
                .expect("Read blit fragment shader as SPIR-V"),
        );

        let pipeline =
            device.create_render_pipeline(&wgpu::RenderPipelineDescriptor {
                layout: &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::Cw,
                    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,
                    color_blend: wgpu::BlendDescriptor {
                        src_factor: wgpu::BlendFactor::SrcAlpha,
                        dst_factor: wgpu::BlendFactor::OneMinusSrcAlpha,
                        operation: wgpu::BlendOperation::Add,
                    },
                    alpha_blend: wgpu::BlendDescriptor {
                        src_factor: wgpu::BlendFactor::One,
                        dst_factor: wgpu::BlendFactor::OneMinusSrcAlpha,
                        operation: wgpu::BlendOperation::Add,
                    },
                    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,
            });

        Blit {
            format,
            pipeline,
            constants: constant_bind_group,
            texture_layout,
            sample_count: antialiasing.sample_count(),
            targets: None,
        }
    }

    pub fn targets(
        &mut self,
        device: &wgpu::Device,
        width: u32,
        height: u32,
    ) -> (&wgpu::TextureView, &wgpu::TextureView) {
        match &mut self.targets {
            None => {
                self.targets = Some(Targets::new(
                    &device,
                    self.format,
                    &self.texture_layout,
                    self.sample_count,
                    width,
                    height,
                ));
            }
            Some(targets) => {
                if targets.width != width || targets.height != height {
                    self.targets = Some(Targets::new(
                        &device,
                        self.format,
                        &self.texture_layout,
                        self.sample_count,
                        width,
                        height,
                    ));
                }
            }
        }

        let targets = self.targets.as_ref().unwrap();

        (&targets.attachment, &targets.resolve)
    }

    pub fn draw(
        &self,
        encoder: &mut wgpu::CommandEncoder,
        target: &wgpu::TextureView,
    ) {
        let mut render_pass =
            encoder.begin_render_pass(&wgpu::RenderPassDescriptor {
                color_attachments: &[
                    wgpu::RenderPassColorAttachmentDescriptor {
                        attachment: target,
                        resolve_target: None,
                        load_op: wgpu::LoadOp::Load,
                        store_op: wgpu::StoreOp::Store,
                        clear_color: wgpu::Color {
                            r: 0.0,
                            g: 0.0,
                            b: 0.0,
                            a: 0.0,
                        },
                    },
                ],
                depth_stencil_attachment: None,
            });

        render_pass.set_pipeline(&self.pipeline);
        render_pass.set_bind_group(0, &self.constants, &[]);
        render_pass.set_bind_group(
            1,
            &self.targets.as_ref().unwrap().bind_group,
            &[],
        );
        render_pass.draw(0..6, 0..1);
    }
}

#[derive(Debug)]
struct Targets {
    attachment: wgpu::TextureView,
    resolve: wgpu::TextureView,
    bind_group: wgpu::BindGroup,
    width: u32,
    height: u32,
}

impl Targets {
    pub fn new(
        device: &wgpu::Device,
        format: wgpu::TextureFormat,
        texture_layout: &wgpu::BindGroupLayout,
        sample_count: u32,
        width: u32,
        height: u32,
    ) -> Targets {
        let extent = wgpu::Extent3d {
            width,
            height,
            depth: 1,
        };

        let attachment = device.create_texture(&wgpu::TextureDescriptor {
            label: None,
            size: extent,
            array_layer_count: 1,
            mip_level_count: 1,
            sample_count,
            dimension: wgpu::TextureDimension::D2,
            format,
            usage: wgpu::TextureUsage::OUTPUT_ATTACHMENT,
        });

        let resolve = device.create_texture(&wgpu::TextureDescriptor {
            label: None,
            size: extent,
            array_layer_count: 1,
            mip_level_count: 1,
            sample_count: 1,
            dimension: wgpu::TextureDimension::D2,
            format,
            usage: wgpu::TextureUsage::OUTPUT_ATTACHMENT
                | wgpu::TextureUsage::SAMPLED,
        });

        let attachment = attachment.create_default_view();
        let resolve = resolve.create_default_view();

        let bind_group = device.create_bind_group(&wgpu::BindGroupDescriptor {
            label: None,
            layout: texture_layout,
            bindings: &[wgpu::Binding {
                binding: 0,
                resource: wgpu::BindingResource::TextureView(&resolve),
            }],
        });

        Targets {
            attachment,
            resolve,
            bind_group,
            width,
            height,
        }
    }
}