using System;
using System.Numerics;
using System.Runtime.InteropServices;
using System.Text;
using TerraFX.Interop.DirectX;
using TerraFX.Interop.Windows;

namespace Auspex.Rendering.Direct3D;

internal sealed class TriangleFillShader : IDisposable
{
	public struct Constants
	{
		public Matrix4x4 ViewProj;

		public Vector2 PixelToUv;
	}

	public struct Instance
	{
		public Vector3 Point;

		public Vector4 Color;

		public Vector4 FadeParams;
	}

	public sealed class Data : HlslShaderData<Instance>
	{
		public sealed class Builder : HlslShaderBuilder<Instance>
		{
			internal Builder(FrameRenderContext ctx, Data data)
				: base(data._buffer.Map(ctx))
			{
			}

			public void Add(Vector3 world, Vector4 color, AxDxParams p)
			{
				_inner.Add(new Instance
				{
					Point = world,
					Color = color,
					FadeParams = new Vector4(p.OccludedAlpha, p.OcclusionTolerance, p.FadeStart, p.FadeStop)
				});
			}
		}

		public Data(FrameRenderContext ctx, int maxCount, bool dynamic)
			: base("Triangle", ctx, maxCount, dynamic)
		{
		}

		public Builder Map(FrameRenderContext ctx)
		{
			return new Builder(ctx, this);
		}

		public void DrawSubset(FrameRenderContext ctx, int firstPoint, int numPoints)
		{
			DrawVertices(ctx, firstPoint, numPoints);
		}

		public void DrawAll(FrameRenderContext ctx)
		{
			DrawVertices(ctx, 0, _buffer.CurElements);
		}
	}

	private unsafe ID3D11Buffer* _constantBuffer;

	private unsafe ID3D11InputLayout* _il;

	private unsafe ID3D11VertexShader* _vs;

	private unsafe ID3D11PixelShader* _ps;

	public unsafe TriangleFillShader(FrameRenderContext ctx)
	{
		byte[] bytes = Encoding.UTF8.GetBytes("cbuffer Constants : register(b0)\n{\n    float4x4 viewProj;\n    float2 pixelToUv;\n};\n\nTexture2D<float4> _sceneDepth : register(t0);\nSamplerState _occlusionSampler\n{\n    Filter = MIN_MAG_MIP_POINT;\n    AddressU = CLAMP;\n    AddressV = CLAMP;\n};\n\n// fadeParams: x=OccludedAlpha, y=OcclusionTolerance (m), z=FadeStart (m), w=FadeStop (m).\nfloat4 applyShared(float4 color, float3 projPos, float4 fadeParams)\n{\n    float2 uv = projPos.xy * pixelToUv;\n    float sceneNdcZ = _sceneDepth.Sample(_occlusionSampler, uv).r;\n\n    float near = viewProj._m32;\n    float shapeWorldZ = near / max(projPos.z, 1e-6);\n    float sceneWorldZ = near / max(sceneNdcZ, 1e-6);\n\n    float behindMeters = max(shapeWorldZ - sceneWorldZ, 0.0);\n    float occlusion = behindMeters <= fadeParams.y ? 1.0 : fadeParams.x;\n\n    float distanceFactor = 1.0;\n    if (fadeParams.w < 1e10)\n    {\n        float range = max(fadeParams.w - fadeParams.z, 1e-4);\n        distanceFactor = saturate((fadeParams.w - shapeWorldZ) / range);\n    }\n\n    color.a *= occlusion * distanceFactor;\n    return color;\n}\n\nstruct Point\n{\n    float3 pos : WORLD;\n    float4 color : COLOR;\n    float4 fadeParams : FADEPARAMS;\n};\n\nstruct VSOutput\n{\n    float4 projPos : SV_POSITION;\n    float4 color : COLOR;\n    float4 fadeParams : FADEPARAMS;\n};\n\nVSOutput vs(Point v)\n{\n    VSOutput vs;\n    vs.projPos = mul(float4(v.pos, 1), viewProj);\n    vs.color = v.color;\n    vs.fadeParams = v.fadeParams;\n    return vs;\n}\n\nfloat4 ps(VSOutput input) : SV_TARGET\n{\n    return applyShared(input.color, input.projPos.xyz, input.fadeParams);\n}");
		CompileShader(bytes, "vs"u8, "vs_5_0"u8, out var blob, "Point VS");
		CompileShader(bytes, "ps"u8, "ps_5_0"u8, out var blob2, "Point 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 = 80u,
			Usage = D3D11_USAGE.D3D11_USAGE_DEFAULT,
			BindFlags = 4u
		};
		ID3D11Buffer* constantBuffer = default(ID3D11Buffer*);
		Marshal.ThrowExceptionForHR(ctx.Device->CreateBuffer(&d3D11_BUFFER_DESC, null, &constantBuffer));
		_constantBuffer = constantBuffer;
		fixed (byte* semanticName = "WORLD"u8)
		{
			fixed (byte* semanticName2 = "COLOR"u8)
			{
				fixed (byte* semanticName3 = "FADEPARAMS"u8)
				{
					D3D11_INPUT_ELEMENT_DESC* ptr = stackalloc D3D11_INPUT_ELEMENT_DESC[3];
					*ptr = new D3D11_INPUT_ELEMENT_DESC
					{
						SemanticName = (sbyte*)semanticName,
						SemanticIndex = 0u,
						Format = DXGI_FORMAT.DXGI_FORMAT_R32G32B32_FLOAT,
						AlignedByteOffset = uint.MaxValue,
						InputSlot = 0u,
						InputSlotClass = D3D11_INPUT_CLASSIFICATION.D3D11_INPUT_PER_VERTEX_DATA,
						InstanceDataStepRate = 0u
					};
					ptr[1] = new D3D11_INPUT_ELEMENT_DESC
					{
						SemanticName = (sbyte*)semanticName2,
						SemanticIndex = 0u,
						Format = DXGI_FORMAT.DXGI_FORMAT_R32G32B32A32_FLOAT,
						AlignedByteOffset = uint.MaxValue,
						InputSlot = 0u,
						InputSlotClass = D3D11_INPUT_CLASSIFICATION.D3D11_INPUT_PER_VERTEX_DATA,
						InstanceDataStepRate = 0u
					};
					ptr[2] = new D3D11_INPUT_ELEMENT_DESC
					{
						SemanticName = (sbyte*)semanticName3,
						SemanticIndex = 0u,
						Format = DXGI_FORMAT.DXGI_FORMAT_R32G32B32A32_FLOAT,
						AlignedByteOffset = uint.MaxValue,
						InputSlot = 0u,
						InputSlotClass = D3D11_INPUT_CLASSIFICATION.D3D11_INPUT_PER_VERTEX_DATA,
						InstanceDataStepRate = 0u
					};
					ID3D11InputLayout* il = default(ID3D11InputLayout*);
					Marshal.ThrowExceptionForHR(ctx.Device->CreateInputLayout(ptr, 3u, blob->GetBufferPointer(), blob->GetBufferSize(), &il));
					_il = il;
				}
			}
		}
		blob->Release();
		blob2->Release();
	}

	public unsafe void Dispose()
	{
		if (_constantBuffer != null)
		{
			_constantBuffer->Release();
			_constantBuffer = null;
		}
		if (_il != null)
		{
			_il->Release();
			_il = 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)
	{
		consts.ViewProj = Matrix4x4.Transpose(consts.ViewProj);
		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->IASetInputLayout(_il);
		ctx.Context->VSSetShader(_vs, null, 0u);
		ID3D11Buffer* constantBuffer = _constantBuffer;
		ctx.Context->VSSetConstantBuffers(0u, 1u, &constantBuffer);
		ctx.Context->PSSetShader(_ps, null, 0u);
		ctx.Context->PSSetConstantBuffers(0u, 1u, &constantBuffer);
		ctx.Context->GSSetShader(null, null, 0u);
	}

	public void Draw(FrameRenderContext ctx, Data data)
	{
		Bind(ctx);
		data.DrawAll(ctx);
	}

	internal unsafe static void CompileShader(ReadOnlySpan<byte> source, ReadOnlySpan<byte> entryPoint, ReadOnlySpan<byte> target, out ID3DBlob* blob, string label)
	{
		ID3DBlob* ptr = null;
		ID3DBlob* ptr2 = null;
		HRESULT hRESULT;
		fixed (byte* pSrcData = source)
		{
			fixed (byte* pEntrypoint = entryPoint)
			{
				fixed (byte* pTarget = target)
				{
					hRESULT = DirectX.D3DCompile(pSrcData, (nuint)source.Length, null, null, null, (sbyte*)pEntrypoint, (sbyte*)pTarget, 0u, 0u, &ptr, &ptr2);
				}
			}
		}
		string text = null;
		if (ptr2 != null)
		{
			text = Encoding.UTF8.GetString((byte*)ptr2->GetBufferPointer(), (int)(nuint)ptr2->GetBufferSize()).TrimEnd('\0');
			ptr2->Release();
		}
		AuspexService.Log.Debug(label + " compile: " + text);
		if (hRESULT.FAILED)
		{
			if (ptr != null)
			{
				ptr->Release();
			}
			throw new InvalidOperationException("Shader compilation failed (" + label + "): " + text);
		}
		blob = ptr;
	}
}