using System;
using System.Runtime.InteropServices;
using TerraFX.Interop.DirectX;

namespace Auspex.Rendering.Direct3D;

internal sealed class FullscreenPassShader : IDisposable
{
	public struct Constants
	{
		public float MaxAlpha;

		public float ClipNativeUI;
	}

	private unsafe ID3D11Buffer* _constantBuffer;

	private unsafe ID3D11VertexShader* _vs;

	private unsafe ID3D11PixelShader* _ps;

	public unsafe FullscreenPassShader(FrameRenderContext ctx)
	{
		ReadOnlySpan<byte> source = "struct Constants\n{\n    float maxAlpha;\n    float clipNativeUI;\n};\nConstants k : register(b0);\n\nTexture2D<float4> inputTexture : register(t0);\nTexture2D<float4> maskTexture  : register(t1);\n\nSamplerState TextureSampler\n{\n    Filter = MIN_MAG_MIP_POINT;\n    AddressU = CLAMP;\n    AddressV = CLAMP;\n};\n\nstruct VSOutput\n{\n    float4 pos : SV_POSITION;\n    float2 uv: TEXCOORD;\n};\n\nVSOutput vs(uint id : SV_VertexID)\n{\n    VSOutput output;\n\tfloat2 uv = float2((id << 1) & 2, id & 2);\n\toutput.pos = float4(uv * float2(2, -2) + float2(-1, 1), 0, 1);\n    output.uv = uv;\n    return output;\n}\n\nfloat4 ps(VSOutput input) : SV_Target\n{\n    float4 color = inputTexture.Sample(TextureSampler, input.uv);\n    if (color.a > 0)\n    {\n        color.rgb /= color.a;\n    }\n    float maskAlpha = 1;\n    if (k.clipNativeUI > 0.5)\n    {\n        float4 mask = maskTexture.Sample(TextureSampler, input.uv);\n        // Apply mask alpha squared\n        // (I don't think this is mathematically correct but it looks better)\n        maskAlpha = 1 - mask.a;\n        maskAlpha *= maskAlpha;\n    }\n    color.a = min(color.a, k.maxAlpha) * maskAlpha;\n    return color;\n}"u8;
		TriangleFillShader.CompileShader(source, "vs"u8, "vs_5_0"u8, out var blob, "FSP VS");
		TriangleFillShader.CompileShader(source, "ps"u8, "ps_5_0"u8, out var blob2, "FSP PS");
		ID3D11VertexShader* vs = default(ID3D11VertexShader*);
		Marshal.ThrowExceptionForHR(ctx.Device->CreateVertexShader(blob->GetBufferPointer(), blob->GetBufferSize(), null, &vs));
		_vs = vs;
		ID3D11PixelShader* ps = default(ID3D11PixelShader*);
		Marshal.ThrowExceptionForHR(ctx.Device->CreatePixelShader(blob2->GetBufferPointer(), blob2->GetBufferSize(), null, &ps));
		_ps = ps;
		D3D11_BUFFER_DESC d3D11_BUFFER_DESC = new D3D11_BUFFER_DESC
		{
			ByteWidth = 16u,
			Usage = D3D11_USAGE.D3D11_USAGE_DEFAULT,
			BindFlags = 4u
		};
		ID3D11Buffer* constantBuffer = default(ID3D11Buffer*);
		Marshal.ThrowExceptionForHR(ctx.Device->CreateBuffer(&d3D11_BUFFER_DESC, null, &constantBuffer));
		_constantBuffer = constantBuffer;
		blob->Release();
		blob2->Release();
	}

	public unsafe void Dispose()
	{
		if (_constantBuffer != null)
		{
			_constantBuffer->Release();
			_constantBuffer = null;
		}
		if (_vs != null)
		{
			_vs->Release();
			_vs = null;
		}
		if (_ps != null)
		{
			_ps->Release();
			_ps = null;
		}
		GC.SuppressFinalize(this);
	}

	public unsafe void UpdateConstants(FrameRenderContext ctx, Constants consts)
	{
		ctx.Context->UpdateSubresource((ID3D11Resource*)_constantBuffer, 0u, null, &consts, 0u, 0u);
	}

	public unsafe void Bind(FrameRenderContext ctx)
	{
		ctx.Context->IASetPrimitiveTopology(D3D_PRIMITIVE_TOPOLOGY.D3D_PRIMITIVE_TOPOLOGY_TRIANGLELIST);
		ctx.Context->VSSetShader(_vs, null, 0u);
		ctx.Context->PSSetShader(_ps, null, 0u);
		ID3D11Buffer* constantBuffer = _constantBuffer;
		ctx.Context->PSSetConstantBuffers(0u, 1u, &constantBuffer);
		ctx.Context->GSSetShader(null, null, 0u);
	}

	public unsafe void Draw(FrameRenderContext ctx, ID3D11ShaderResourceView* baseSRV, ID3D11ShaderResourceView* maskSRV)
	{
		ctx.Context->PSSetShaderResources(0u, 1u, &baseSRV);
		ctx.Context->PSSetShaderResources(1u, 1u, &maskSRV);
		Bind(ctx);
		ctx.Context->Draw(3u, 0u);
		ID3D11ShaderResourceView* ptr = null;
		ctx.Context->PSSetShaderResources(0u, 1u, &ptr);
		ctx.Context->PSSetShaderResources(1u, 1u, &ptr);
	}
}