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

namespace Auspex.Rendering.Direct3D;

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

		public Vector2 PixelToUv;
	}

	public struct Instance
	{
		public Vector3 Origin;

		public float InnerRadius;

		public float OuterRadius;

		public float MinAngle;

		public float MaxAngle;

		public float NumSegments;

		public Vector4 ColorOrigin;

		public Vector4 ColorEnd;

		public float OccludedAlpha;

		public float OcclusionTolerance;

		public float FadeStart;

		public float FadeStop;
	}

	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, float innerRadius, float outerRadius, float minAngle, float maxAngle, Vector4 colorOrigin, Vector4 colorEnd, float numSegments, AxDxParams p)
			{
				_inner.Add(new Instance
				{
					Origin = world,
					InnerRadius = innerRadius,
					OuterRadius = outerRadius,
					MinAngle = minAngle,
					MaxAngle = maxAngle,
					NumSegments = numSegments,
					ColorOrigin = colorOrigin,
					ColorEnd = colorEnd,
					OccludedAlpha = p.OccludedAlpha,
					OcclusionTolerance = p.OcclusionTolerance,
					FadeStart = p.FadeStart,
					FadeStop = p.FadeStop
				});
			}
		}

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

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

		public unsafe void DrawAll(FrameRenderContext ctx)
		{
			ID3D11Buffer* buffer = _buffer.Buffer;
			uint elementSize = (uint)_buffer.ElementSize;
			uint num = 0u;
			ctx.Context->IASetVertexBuffers(0u, 1u, &buffer, &elementSize, &num);
			ctx.Context->DrawInstanced(722u, (uint)_buffer.CurElements, 0u, 0u);
		}
	}

	private const int VerticesPerInstance = 722;

	private unsafe ID3D11Buffer* _constantBuffer;

	private unsafe ID3D11InputLayout* _il;

	private unsafe ID3D11VertexShader* _vs;

	private unsafe ID3D11PixelShader* _ps;

	public unsafe FanFillShader(FrameRenderContext ctx)
	{
		byte[] bytes = Encoding.UTF8.GetBytes("#define PI 3.14159265359f\n#define MAX_SEGMENTS 360\n\ncbuffer 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 Fan\n{\n    float3 origin : WORLD;\n    float innerRadius : RADIUS0;\n    float outerRadius : RADIUS1;\n    float minAngle : ANGLE0;\n    float maxAngle : ANGLE1;\n    float numSegments : NUMSEGMENTS;\n    float4 colorOrigin : INSTANCECOLOR0;\n    float4 colorEnd : INSTANCECOLOR1;\n    float4 fadeParams : FADEPARAMS;\n};\n\nstruct VSOutput\n{\n    float4 projPos : SV_POSITION;\n    float4 color : COLOR;\n    float2 tex : TEXCOORD;\n    float4 fadeParams : FADEPARAMS;\n};\n\nVSOutput vs(in Fan instance, uint vertexId: SV_VERTEXID, uint instanceId: SV_INSTANCEID)\n{\n    VSOutput o;\n\n    uint segs = (uint)instance.numSegments;\n    uint i = min(vertexId / 2, segs);\n\n    float radius = 0;\n    if (vertexId % 2 == 0) {\n        o.color = instance.colorOrigin;\n        o.tex.y = 0;\n        radius = instance.innerRadius;\n    } else {\n        o.color = instance.colorEnd;\n        o.tex.y = instance.outerRadius - instance.innerRadius;\n        radius = instance.outerRadius;\n    }\n    float totalAngle = instance.maxAngle - instance.minAngle;\n    float angleStep = totalAngle / instance.numSegments;\n    float angle = PI / 2 + instance.minAngle + i * angleStep;\n    float3 offset = radius * float3(cos(angle), 0, sin(angle));\n\n    o.tex.x = angle;\n    o.projPos = mul(float4(instance.origin + offset, 1.0), viewProj);\n    o.fadeParams = instance.fadeParams;\n    return o;\n}\n\nfloat4 ps(VSOutput input) : SV_TARGET\n{\n    return applyShared(input.color, input.projPos.xyz, input.fadeParams);\n}");
		TriangleFillShader.CompileShader(bytes, "vs"u8, "vs_5_0"u8, out var blob, "Circle VS");
		TriangleFillShader.CompileShader(bytes, "ps"u8, "ps_5_0"u8, out var blob2, "Circle 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 = "RADIUS"u8)
			{
				fixed (byte* semanticName3 = "ANGLE"u8)
				{
					fixed (byte* semanticName4 = "NUMSEGMENTS"u8)
					{
						fixed (byte* semanticName5 = "INSTANCECOLOR"u8)
						{
							fixed (byte* semanticName6 = "FADEPARAMS"u8)
							{
								D3D11_INPUT_ELEMENT_DESC* ptr = stackalloc D3D11_INPUT_ELEMENT_DESC[9];
								*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_INSTANCE_DATA,
									InstanceDataStepRate = 1u
								};
								ptr[1] = new D3D11_INPUT_ELEMENT_DESC
								{
									SemanticName = (sbyte*)semanticName2,
									SemanticIndex = 0u,
									Format = DXGI_FORMAT.DXGI_FORMAT_R32_FLOAT,
									AlignedByteOffset = uint.MaxValue,
									InputSlot = 0u,
									InputSlotClass = D3D11_INPUT_CLASSIFICATION.D3D11_INPUT_PER_INSTANCE_DATA,
									InstanceDataStepRate = 1u
								};
								ptr[2] = new D3D11_INPUT_ELEMENT_DESC
								{
									SemanticName = (sbyte*)semanticName2,
									SemanticIndex = 1u,
									Format = DXGI_FORMAT.DXGI_FORMAT_R32_FLOAT,
									AlignedByteOffset = uint.MaxValue,
									InputSlot = 0u,
									InputSlotClass = D3D11_INPUT_CLASSIFICATION.D3D11_INPUT_PER_INSTANCE_DATA,
									InstanceDataStepRate = 1u
								};
								ptr[3] = new D3D11_INPUT_ELEMENT_DESC
								{
									SemanticName = (sbyte*)semanticName3,
									SemanticIndex = 0u,
									Format = DXGI_FORMAT.DXGI_FORMAT_R32_FLOAT,
									AlignedByteOffset = uint.MaxValue,
									InputSlot = 0u,
									InputSlotClass = D3D11_INPUT_CLASSIFICATION.D3D11_INPUT_PER_INSTANCE_DATA,
									InstanceDataStepRate = 1u
								};
								ptr[4] = new D3D11_INPUT_ELEMENT_DESC
								{
									SemanticName = (sbyte*)semanticName3,
									SemanticIndex = 1u,
									Format = DXGI_FORMAT.DXGI_FORMAT_R32_FLOAT,
									AlignedByteOffset = uint.MaxValue,
									InputSlot = 0u,
									InputSlotClass = D3D11_INPUT_CLASSIFICATION.D3D11_INPUT_PER_INSTANCE_DATA,
									InstanceDataStepRate = 1u
								};
								ptr[5] = new D3D11_INPUT_ELEMENT_DESC
								{
									SemanticName = (sbyte*)semanticName4,
									SemanticIndex = 0u,
									Format = DXGI_FORMAT.DXGI_FORMAT_R32_FLOAT,
									AlignedByteOffset = uint.MaxValue,
									InputSlot = 0u,
									InputSlotClass = D3D11_INPUT_CLASSIFICATION.D3D11_INPUT_PER_INSTANCE_DATA,
									InstanceDataStepRate = 1u
								};
								ptr[6] = new D3D11_INPUT_ELEMENT_DESC
								{
									SemanticName = (sbyte*)semanticName5,
									SemanticIndex = 0u,
									Format = DXGI_FORMAT.DXGI_FORMAT_R32G32B32A32_FLOAT,
									AlignedByteOffset = uint.MaxValue,
									InputSlot = 0u,
									InputSlotClass = D3D11_INPUT_CLASSIFICATION.D3D11_INPUT_PER_INSTANCE_DATA,
									InstanceDataStepRate = 1u
								};
								ptr[7] = new D3D11_INPUT_ELEMENT_DESC
								{
									SemanticName = (sbyte*)semanticName5,
									SemanticIndex = 1u,
									Format = DXGI_FORMAT.DXGI_FORMAT_R32G32B32A32_FLOAT,
									AlignedByteOffset = uint.MaxValue,
									InputSlot = 0u,
									InputSlotClass = D3D11_INPUT_CLASSIFICATION.D3D11_INPUT_PER_INSTANCE_DATA,
									InstanceDataStepRate = 1u
								};
								ptr[8] = new D3D11_INPUT_ELEMENT_DESC
								{
									SemanticName = (sbyte*)semanticName6,
									SemanticIndex = 0u,
									Format = DXGI_FORMAT.DXGI_FORMAT_R32G32B32A32_FLOAT,
									AlignedByteOffset = uint.MaxValue,
									InputSlot = 0u,
									InputSlotClass = D3D11_INPUT_CLASSIFICATION.D3D11_INPUT_PER_INSTANCE_DATA,
									InstanceDataStepRate = 1u
								};
								ID3D11InputLayout* il = default(ID3D11InputLayout*);
								Marshal.ThrowExceptionForHR(ctx.Device->CreateInputLayout(ptr, 9u, 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_TRIANGLESTRIP);
		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);
	}
}