//! DirectX Backend (Windows)
//!
//! Provides GPU acceleration using DirectX 11 and DirectX 12

use super::super::Handle;
use super::backend::GpuDevice;
use super::types::*;
use crate::fitz::geometry::Matrix;

// ============================================================================
// DirectX 11
// ============================================================================

/// DirectX 11 device implementation
#[cfg(target_os = "windows")]
pub struct DirectX11Device {
    capabilities: GpuCapabilities,
    /// ID3D11Device
    _device: u64,
    /// ID3D11DeviceContext
    _context: u64,
}

#[cfg(target_os = "windows")]
impl DirectX11Device {
    /// Create a new DirectX 11 device
    pub fn new() -> GpuResult<Self> {
        // D3D11CreateDevice(nullptr, D3D_DRIVER_TYPE_HARDWARE, nullptr,
        //     D3D11_CREATE_DEVICE_BGRA_SUPPORT, nullptr, 0,
        //     D3D11_SDK_VERSION, &device, nullptr, &context);

        let capabilities = GpuCapabilities {
            max_texture_size: 16384,
            max_texture_units: 128,
            compute_shaders: true,
            geometry_shaders: true,
            tessellation: true,
            max_msaa_samples: 8,
            float_textures: true,
            instancing: true,
            vram_mb: 0,
            device_name: "DirectX 11 Device".into(),
            vendor_name: "Unknown".into(),
            driver_version: "DirectX 11.1".into(),
        };

        Ok(Self {
            capabilities,
            _device: 0,
            _context: 0,
        })
    }
}

#[cfg(target_os = "windows")]
impl GpuDevice for DirectX11Device {
    fn backend(&self) -> GpuBackendType {
        GpuBackendType::DirectX11
    }

    fn capabilities(&self) -> &GpuCapabilities {
        &self.capabilities
    }

    fn create_texture(&self, width: u32, height: u32, format: GpuFormat) -> GpuResult<GpuTexture> {
        // D3D11_TEXTURE2D_DESC desc = {};
        // desc.Width = width;
        // desc.Height = height;
        // desc.Format = DXGI_FORMAT_R8G8B8A8_UNORM;
        // desc.BindFlags = D3D11_BIND_SHADER_RESOURCE | D3D11_BIND_RENDER_TARGET;
        // device->CreateTexture2D(&desc, nullptr, &texture);

        let mut texture = GpuTexture::new(width, height, format, GpuBackendType::DirectX11);
        texture.native_handle = 1;
        Ok(texture)
    }

    fn destroy_texture(&self, _texture: &GpuTexture) -> GpuResult<()> {
        // texture->Release();
        Ok(())
    }

    fn upload_texture(
        &self,
        texture: &mut GpuTexture,
        _data: &[u8],
        _stride: u32,
    ) -> GpuResult<()> {
        // context->UpdateSubresource(texture, 0, nullptr, data, stride, 0);
        let _ = texture;
        Ok(())
    }

    fn download_texture(
        &self,
        texture: &GpuTexture,
        _data: &mut [u8],
        _stride: u32,
    ) -> GpuResult<()> {
        // Create staging texture, copy, map, read
        let _ = texture;
        Ok(())
    }

    fn clear_texture(&self, texture: &mut GpuTexture, color: [f32; 4]) -> GpuResult<()> {
        // context->ClearRenderTargetView(rtv, color);
        let _ = (texture, color);
        Ok(())
    }

    fn create_shader(&self, _vertex_src: &str, _fragment_src: &str) -> GpuResult<GpuShader> {
        // D3DCompile for vertex shader
        // D3DCompile for pixel shader
        // device->CreateVertexShader
        // device->CreatePixelShader
        let shader = GpuShader::new("shader", GpuBackendType::DirectX11);
        Ok(shader)
    }

    fn destroy_shader(&self, _shader: &GpuShader) -> GpuResult<()> {
        Ok(())
    }

    fn create_buffer(&self, size: usize, usage: GpuBufferUsage) -> GpuResult<GpuBuffer> {
        // D3D11_BUFFER_DESC desc = {};
        // desc.ByteWidth = size;
        // desc.BindFlags = D3D11_BIND_VERTEX_BUFFER; // or INDEX/CONSTANT
        // device->CreateBuffer(&desc, nullptr, &buffer);
        let buffer = GpuBuffer::new(size, usage, GpuBackendType::DirectX11);
        Ok(buffer)
    }

    fn destroy_buffer(&self, _buffer: &GpuBuffer) -> GpuResult<()> {
        Ok(())
    }

    fn upload_buffer(&self, buffer: &mut GpuBuffer, _data: &[u8], _offset: usize) -> GpuResult<()> {
        // context->Map, memcpy, Unmap
        let _ = buffer;
        Ok(())
    }

    fn render_page(
        &self,
        page: Handle,
        texture: &mut GpuTexture,
        transform: &Matrix,
    ) -> GpuResult<()> {
        // Set render target
        // Set viewport
        // Set shaders
        // Set constant buffers with transform
        // Draw indexed
        let _ = (page, texture, transform);
        Ok(())
    }

    fn composite(
        &self,
        src: &GpuTexture,
        dst: &mut GpuTexture,
        x: i32,
        y: i32,
        blend_mode: GpuBlendMode,
    ) -> GpuResult<()> {
        let _ = (src, dst, x, y, blend_mode);
        Ok(())
    }

    fn draw_quad(
        &self,
        texture: &GpuTexture,
        dst: &mut GpuTexture,
        src_rect: [f32; 4],
        dst_rect: [f32; 4],
        color: [f32; 4],
    ) -> GpuResult<()> {
        let _ = (texture, dst, src_rect, dst_rect, color);
        Ok(())
    }

    fn flush(&self) -> GpuResult<()> {
        // context->Flush();
        Ok(())
    }

    fn finish(&self) -> GpuResult<()> {
        // Create query, end query, wait for data
        Ok(())
    }
}

// ============================================================================
// DirectX 12
// ============================================================================

/// DirectX 12 device implementation
#[cfg(target_os = "windows")]
pub struct DirectX12Device {
    capabilities: GpuCapabilities,
    /// ID3D12Device
    _device: u64,
    /// ID3D12CommandQueue
    _command_queue: u64,
    /// ID3D12CommandAllocator
    _command_allocator: u64,
    /// ID3D12GraphicsCommandList
    _command_list: u64,
    /// ID3D12Fence
    _fence: u64,
    /// Fence value
    _fence_value: u64,
}

#[cfg(target_os = "windows")]
impl DirectX12Device {
    /// Create a new DirectX 12 device
    pub fn new() -> GpuResult<Self> {
        // D3D12CreateDevice(nullptr, D3D_FEATURE_LEVEL_12_0, IID_PPV_ARGS(&device));
        // Create command queue, allocator, list, fence

        let capabilities = GpuCapabilities {
            max_texture_size: 16384,
            max_texture_units: 128,
            compute_shaders: true,
            geometry_shaders: true,
            tessellation: true,
            max_msaa_samples: 8,
            float_textures: true,
            instancing: true,
            vram_mb: 0,
            device_name: "DirectX 12 Device".into(),
            vendor_name: "Unknown".into(),
            driver_version: "DirectX 12".into(),
        };

        Ok(Self {
            capabilities,
            _device: 0,
            _command_queue: 0,
            _command_allocator: 0,
            _command_list: 0,
            _fence: 0,
            _fence_value: 0,
        })
    }
}

#[cfg(target_os = "windows")]
impl GpuDevice for DirectX12Device {
    fn backend(&self) -> GpuBackendType {
        GpuBackendType::DirectX12
    }

    fn capabilities(&self) -> &GpuCapabilities {
        &self.capabilities
    }

    fn create_texture(&self, width: u32, height: u32, format: GpuFormat) -> GpuResult<GpuTexture> {
        // D3D12_RESOURCE_DESC desc = {};
        // desc.Dimension = D3D12_RESOURCE_DIMENSION_TEXTURE2D;
        // desc.Width = width;
        // desc.Height = height;
        // device->CreateCommittedResource(...);

        let mut texture = GpuTexture::new(width, height, format, GpuBackendType::DirectX12);
        texture.native_handle = 1;
        Ok(texture)
    }

    fn destroy_texture(&self, _texture: &GpuTexture) -> GpuResult<()> {
        Ok(())
    }

    fn upload_texture(
        &self,
        texture: &mut GpuTexture,
        _data: &[u8],
        _stride: u32,
    ) -> GpuResult<()> {
        // Create upload heap, copy to upload heap, copy to texture via command list
        let _ = texture;
        Ok(())
    }

    fn download_texture(
        &self,
        texture: &GpuTexture,
        _data: &mut [u8],
        _stride: u32,
    ) -> GpuResult<()> {
        // Copy to readback heap, map, read
        let _ = texture;
        Ok(())
    }

    fn clear_texture(&self, texture: &mut GpuTexture, color: [f32; 4]) -> GpuResult<()> {
        // commandList->ClearRenderTargetView(rtv, color, 0, nullptr);
        let _ = (texture, color);
        Ok(())
    }

    fn create_shader(&self, _vertex_src: &str, _fragment_src: &str) -> GpuResult<GpuShader> {
        // Compile HLSL to DXIL
        // Create root signature
        // Create pipeline state object
        let shader = GpuShader::new("shader", GpuBackendType::DirectX12);
        Ok(shader)
    }

    fn destroy_shader(&self, _shader: &GpuShader) -> GpuResult<()> {
        Ok(())
    }

    fn create_buffer(&self, size: usize, usage: GpuBufferUsage) -> GpuResult<GpuBuffer> {
        // device->CreateCommittedResource for buffer
        let buffer = GpuBuffer::new(size, usage, GpuBackendType::DirectX12);
        Ok(buffer)
    }

    fn destroy_buffer(&self, _buffer: &GpuBuffer) -> GpuResult<()> {
        Ok(())
    }

    fn upload_buffer(&self, buffer: &mut GpuBuffer, _data: &[u8], _offset: usize) -> GpuResult<()> {
        let _ = buffer;
        Ok(())
    }

    fn render_page(
        &self,
        page: Handle,
        texture: &mut GpuTexture,
        transform: &Matrix,
    ) -> GpuResult<()> {
        // Reset command allocator
        // Reset command list
        // Transition texture to render target
        // Set render targets
        // Set viewport, scissor
        // Set pipeline state
        // Set root signature
        // Set descriptor heaps
        // Draw
        // Transition texture back
        // Close command list
        // Execute
        let _ = (page, texture, transform);
        Ok(())
    }

    fn composite(
        &self,
        src: &GpuTexture,
        dst: &mut GpuTexture,
        x: i32,
        y: i32,
        blend_mode: GpuBlendMode,
    ) -> GpuResult<()> {
        let _ = (src, dst, x, y, blend_mode);
        Ok(())
    }

    fn draw_quad(
        &self,
        texture: &GpuTexture,
        dst: &mut GpuTexture,
        src_rect: [f32; 4],
        dst_rect: [f32; 4],
        color: [f32; 4],
    ) -> GpuResult<()> {
        let _ = (texture, dst, src_rect, dst_rect, color);
        Ok(())
    }

    fn flush(&self) -> GpuResult<()> {
        // Execute command list
        Ok(())
    }

    fn finish(&self) -> GpuResult<()> {
        // Signal fence, wait for fence
        Ok(())
    }
}

// ============================================================================
// HLSL Shaders
// ============================================================================

/// Quad vertex shader (HLSL)
pub const QUAD_VERTEX_SHADER_HLSL: &str = r#"
cbuffer Constants : register(b0) {
    float4x4 projection;
    float4x4 transform;
    float4 color;
};

struct VSInput {
    float2 position : POSITION;
    float2 texcoord : TEXCOORD0;
};

struct VSOutput {
    float4 position : SV_POSITION;
    float2 texcoord : TEXCOORD0;
};

VSOutput main(VSInput input) {
    VSOutput output;
    output.position = mul(projection, mul(transform, float4(input.position, 0.0, 1.0)));
    output.texcoord = input.texcoord;
    return output;
}
"#;

/// Quad pixel shader (HLSL)
pub const QUAD_PIXEL_SHADER_HLSL: &str = r#"
cbuffer Constants : register(b0) {
    float4x4 projection;
    float4x4 transform;
    float4 color;
};

Texture2D tex : register(t0);
SamplerState samp : register(s0);

struct PSInput {
    float4 position : SV_POSITION;
    float2 texcoord : TEXCOORD0;
};

float4 main(PSInput input) : SV_TARGET {
    return tex.Sample(samp, input.texcoord) * color;
}
"#;

/// Path vertex shader (HLSL)
pub const PATH_VERTEX_SHADER_HLSL: &str = r#"
cbuffer Constants : register(b0) {
    float4x4 projection;
    float4x4 transform;
    float4 color;
};

struct VSInput {
    float2 position : POSITION;
};

struct VSOutput {
    float4 position : SV_POSITION;
};

VSOutput main(VSInput input) {
    VSOutput output;
    output.position = mul(projection, mul(transform, float4(input.position, 0.0, 1.0)));
    return output;
}
"#;

/// Path pixel shader (HLSL)
pub const PATH_PIXEL_SHADER_HLSL: &str = r#"
cbuffer Constants : register(b0) {
    float4x4 projection;
    float4x4 transform;
    float4 color;
};

float4 main() : SV_TARGET {
    return color;
}
"#;

#[cfg(all(test, target_os = "windows"))]
mod tests {
    use super::*;

    #[test]
    fn test_create_dx11_device() {
        let device = DirectX11Device::new().unwrap();
        assert_eq!(device.backend(), GpuBackendType::DirectX11);
    }

    #[test]
    fn test_create_dx12_device() {
        let device = DirectX12Device::new().unwrap();
        assert_eq!(device.backend(), GpuBackendType::DirectX12);
    }
}
