use crate::gpu::Gpu;

const ATLAS_FORMAT: wgpu::TextureFormat = wgpu::TextureFormat::R8Unorm;
const INITIAL_INSTANCE_CAP: u64 = 256;

#[repr(C, align(16))]
#[derive(Copy, Clone, Debug, PartialEq, bytemuck::Pod, bytemuck::Zeroable)]
pub struct SdfGlyphInstance {
    pub rect_xywh_px: [f32; 4],
    pub uv_min: [f32; 2],
    pub uv_max: [f32; 2],
    pub color_premul_rgba: [f32; 4],
}

const INSTANCE_STRIDE: u64 = core::mem::size_of::<SdfGlyphInstance>() as u64;

const INSTANCE_ATTRS: [wgpu::VertexAttribute; 4] = wgpu::vertex_attr_array![
    0 => Float32x4,
    1 => Float32x2,
    2 => Float32x2,
    3 => Float32x4,
];

#[repr(C, align(16))]
#[derive(Copy, Clone, bytemuck::Pod, bytemuck::Zeroable)]
struct Frame {
    viewport_px: [f32; 2],
    _pad: [f32; 2],
}

const FRAME_SIZE: u64 = core::mem::size_of::<Frame>() as u64;

pub struct ChromeTextPipeline {
    device: wgpu::Device,
    queue: wgpu::Queue,
    pipeline: wgpu::RenderPipeline,
    uniform_buffer: wgpu::Buffer,
    bind_group: wgpu::BindGroup,
    atlas: wgpu::Texture,
    atlas_extent: u32,
    atlas_version: Option<u64>,
    instance_buffer: wgpu::Buffer,
    instance_capacity: u64,
}

impl ChromeTextPipeline {
    #[must_use]
    pub fn new(gpu: &Gpu, color_format: wgpu::TextureFormat, atlas_extent: u32) -> Self {
        let device = gpu.device().clone();
        let queue = gpu.queue().clone();
        let atlas = create_atlas_texture(&device, atlas_extent);
        let atlas_view = atlas.create_view(&wgpu::TextureViewDescriptor::default());
        let sampler = device.create_sampler(&wgpu::SamplerDescriptor {
            label: Some("bone-render:chrome-text-sampler"),
            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::MipmapFilterMode::Nearest,
            ..Default::default()
        });
        let bind_group_layout = create_bind_group_layout(&device);
        let pipeline = create_pipeline(&device, &bind_group_layout, color_format);
        let uniform_buffer = device.create_buffer(&wgpu::BufferDescriptor {
            label: Some("bone-render:chrome-text-uniform"),
            size: FRAME_SIZE,
            usage: wgpu::BufferUsages::UNIFORM | wgpu::BufferUsages::COPY_DST,
            mapped_at_creation: false,
        });
        let bind_group = device.create_bind_group(&wgpu::BindGroupDescriptor {
            label: Some("bone-render:chrome-text-bg"),
            layout: &bind_group_layout,
            entries: &[
                wgpu::BindGroupEntry {
                    binding: 0,
                    resource: uniform_buffer.as_entire_binding(),
                },
                wgpu::BindGroupEntry {
                    binding: 1,
                    resource: wgpu::BindingResource::TextureView(&atlas_view),
                },
                wgpu::BindGroupEntry {
                    binding: 2,
                    resource: wgpu::BindingResource::Sampler(&sampler),
                },
            ],
        });
        let instance_buffer = create_instance_buffer(&device, INITIAL_INSTANCE_CAP);
        Self {
            device,
            queue,
            pipeline,
            uniform_buffer,
            bind_group,
            atlas,
            atlas_extent,
            atlas_version: None,
            instance_buffer,
            instance_capacity: INITIAL_INSTANCE_CAP,
        }
    }

    pub fn draw(
        &mut self,
        encoder: &mut wgpu::CommandEncoder,
        color_view: &wgpu::TextureView,
        viewport_px: [f32; 2],
        atlas_pixels: &[u8],
        atlas_version: u64,
        instances: &[SdfGlyphInstance],
    ) {
        if instances.is_empty() {
            return;
        }
        if self.atlas_version != Some(atlas_version) {
            self.upload_atlas(atlas_pixels);
            self.atlas_version = Some(atlas_version);
        }
        let frame = Frame {
            viewport_px,
            _pad: [0.0, 0.0],
        };
        self.queue
            .write_buffer(&self.uniform_buffer, 0, bytemuck::bytes_of(&frame));
        let needed = instances.len() as u64;
        if needed > self.instance_capacity {
            let new_cap = needed.next_power_of_two().max(self.instance_capacity * 2);
            self.instance_buffer = create_instance_buffer(&self.device, new_cap);
            self.instance_capacity = new_cap;
        }
        self.queue
            .write_buffer(&self.instance_buffer, 0, bytemuck::cast_slice(instances));
        let mut pass = encoder.begin_render_pass(&wgpu::RenderPassDescriptor {
            label: Some("bone-render:chrome-text-pass"),
            color_attachments: &[Some(wgpu::RenderPassColorAttachment {
                view: color_view,
                resolve_target: None,
                depth_slice: None,
                ops: wgpu::Operations {
                    load: wgpu::LoadOp::Load,
                    store: wgpu::StoreOp::Store,
                },
            })],
            depth_stencil_attachment: None,
            timestamp_writes: None,
            occlusion_query_set: None,
            multiview_mask: None,
        });
        pass.set_pipeline(&self.pipeline);
        pass.set_bind_group(0, &self.bind_group, &[]);
        let used_bytes = needed * INSTANCE_STRIDE;
        pass.set_vertex_buffer(0, self.instance_buffer.slice(0..used_bytes));
        let Ok(count) = u32::try_from(needed) else {
            panic!("chrome text instance count {needed} exceeds u32::MAX");
        };
        pass.draw(0..6, 0..count);
    }

    fn upload_atlas(&self, pixels: &[u8]) {
        let bytes_per_row = self.atlas_extent;
        self.queue.write_texture(
            wgpu::TexelCopyTextureInfo {
                texture: &self.atlas,
                mip_level: 0,
                origin: wgpu::Origin3d::ZERO,
                aspect: wgpu::TextureAspect::All,
            },
            pixels,
            wgpu::TexelCopyBufferLayout {
                offset: 0,
                bytes_per_row: Some(bytes_per_row),
                rows_per_image: Some(self.atlas_extent),
            },
            wgpu::Extent3d {
                width: self.atlas_extent,
                height: self.atlas_extent,
                depth_or_array_layers: 1,
            },
        );
    }
}

impl core::fmt::Debug for ChromeTextPipeline {
    fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
        f.debug_struct("ChromeTextPipeline")
            .field("atlas_extent", &self.atlas_extent)
            .field("atlas_version", &self.atlas_version)
            .field("instance_capacity", &self.instance_capacity)
            .finish_non_exhaustive()
    }
}

fn create_atlas_texture(device: &wgpu::Device, extent: u32) -> wgpu::Texture {
    device.create_texture(&wgpu::TextureDescriptor {
        label: Some("bone-render:chrome-text-atlas"),
        size: wgpu::Extent3d {
            width: extent,
            height: extent,
            depth_or_array_layers: 1,
        },
        mip_level_count: 1,
        sample_count: 1,
        dimension: wgpu::TextureDimension::D2,
        format: ATLAS_FORMAT,
        usage: wgpu::TextureUsages::TEXTURE_BINDING | wgpu::TextureUsages::COPY_DST,
        view_formats: &[],
    })
}

fn create_bind_group_layout(device: &wgpu::Device) -> wgpu::BindGroupLayout {
    device.create_bind_group_layout(&wgpu::BindGroupLayoutDescriptor {
        label: Some("bone-render:chrome-text-bgl"),
        entries: &[
            wgpu::BindGroupLayoutEntry {
                binding: 0,
                visibility: wgpu::ShaderStages::VERTEX_FRAGMENT,
                ty: wgpu::BindingType::Buffer {
                    ty: wgpu::BufferBindingType::Uniform,
                    has_dynamic_offset: false,
                    min_binding_size: wgpu::BufferSize::new(FRAME_SIZE),
                },
                count: None,
            },
            wgpu::BindGroupLayoutEntry {
                binding: 1,
                visibility: wgpu::ShaderStages::FRAGMENT,
                ty: wgpu::BindingType::Texture {
                    sample_type: wgpu::TextureSampleType::Float { filterable: true },
                    view_dimension: wgpu::TextureViewDimension::D2,
                    multisampled: false,
                },
                count: None,
            },
            wgpu::BindGroupLayoutEntry {
                binding: 2,
                visibility: wgpu::ShaderStages::FRAGMENT,
                ty: wgpu::BindingType::Sampler(wgpu::SamplerBindingType::Filtering),
                count: None,
            },
        ],
    })
}

fn create_pipeline(
    device: &wgpu::Device,
    bind_group_layout: &wgpu::BindGroupLayout,
    color_format: wgpu::TextureFormat,
) -> wgpu::RenderPipeline {
    let shader = device.create_shader_module(wgpu::ShaderModuleDescriptor {
        label: Some("bone-render:chrome-text-shader"),
        source: wgpu::ShaderSource::Wgsl(include_str!("chrome_text.wgsl").into()),
    });
    let pipeline_layout = device.create_pipeline_layout(&wgpu::PipelineLayoutDescriptor {
        label: Some("bone-render:chrome-text-layout"),
        bind_group_layouts: &[Some(bind_group_layout)],
        immediate_size: 0,
    });
    device.create_render_pipeline(&wgpu::RenderPipelineDescriptor {
        label: Some("bone-render:chrome-text-pipeline"),
        layout: Some(&pipeline_layout),
        vertex: wgpu::VertexState {
            module: &shader,
            entry_point: Some("vs"),
            compilation_options: wgpu::PipelineCompilationOptions::default(),
            buffers: &[wgpu::VertexBufferLayout {
                array_stride: INSTANCE_STRIDE,
                step_mode: wgpu::VertexStepMode::Instance,
                attributes: &INSTANCE_ATTRS,
            }],
        },
        fragment: Some(wgpu::FragmentState {
            module: &shader,
            entry_point: Some("fs"),
            compilation_options: wgpu::PipelineCompilationOptions::default(),
            targets: &[Some(wgpu::ColorTargetState {
                format: color_format,
                blend: Some(wgpu::BlendState::PREMULTIPLIED_ALPHA_BLENDING),
                write_mask: wgpu::ColorWrites::ALL,
            })],
        }),
        primitive: wgpu::PrimitiveState {
            topology: wgpu::PrimitiveTopology::TriangleList,
            strip_index_format: None,
            front_face: wgpu::FrontFace::Ccw,
            cull_mode: None,
            polygon_mode: wgpu::PolygonMode::Fill,
            conservative: false,
            unclipped_depth: false,
        },
        depth_stencil: None,
        multisample: wgpu::MultisampleState::default(),
        multiview_mask: None,
        cache: None,
    })
}

fn create_instance_buffer(device: &wgpu::Device, capacity: u64) -> wgpu::Buffer {
    device.create_buffer(&wgpu::BufferDescriptor {
        label: Some("bone-render:chrome-text-instances"),
        size: capacity * INSTANCE_STRIDE,
        usage: wgpu::BufferUsages::VERTEX | wgpu::BufferUsages::COPY_DST,
        mapped_at_creation: false,
    })
}
