using System;
using System.Collections.Generic;
using System.Numerics;
using System.Runtime.InteropServices;
using TerraFX.Interop.DirectX;

namespace Auspex.Rendering.Direct3D;

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

	public struct Vertex
	{
		public Vector3 Position;

		public Vector2 UV;

		public Vector4 Color;
	}

	public struct DrawSegment
	{
		public IntPtr TextureSRV;

		public int StartVertex;

		public int VertexCount;
	}

	public sealed class Data : HlslShaderData<Vertex>
	{
		public sealed class Builder : HlslShaderBuilder<Vertex>
		{
			private readonly List<DrawSegment> _segments;

			private IntPtr _currentTexture;

			private int _segmentStart;

			internal Builder(FrameRenderContext ctx, Data data)
				: base(data._buffer.Map(ctx))
			{
				_segments = data._segments;
				_segments.Clear();
				_currentTexture = (IntPtr)0;
				_segmentStart = 0;
			}

			public override void Dispose()
			{
				FinalizeSegment();
				base.Dispose();
			}

			public void SetTexture(IntPtr srv)
			{
				if (srv != _currentTexture)
				{
					FinalizeSegment();
					_currentTexture = srv;
					_segmentStart = _inner.CurElements;
				}
			}

			private void FinalizeSegment()
			{
				int num = _inner.CurElements - _segmentStart;
				if (num > 0 && _currentTexture != (IntPtr)0)
				{
					_segments.Add(new DrawSegment
					{
						TextureSRV = _currentTexture,
						StartVertex = _segmentStart,
						VertexCount = num
					});
				}
			}

			public void Add(Vector3 position, Vector2 uv, Vector4 color)
			{
				_inner.Add(new Vertex
				{
					Position = position,
					UV = uv,
					Color = color
				});
			}
		}

		internal readonly List<DrawSegment> _segments = new List<DrawSegment>();

		internal GpuBuffer<Vertex> Buffer => _buffer;

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

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

	private unsafe ID3D11Buffer* _constantBuffer;

	private unsafe ID3D11InputLayout* _il;

	private unsafe ID3D11VertexShader* _vs;

	private unsafe ID3D11PixelShader* _ps;

	private unsafe ID3D11SamplerState* _sampler;

	public unsafe QuadBlitter(FrameRenderContext ctx)
	{
		ReadOnlySpan<byte> source = "struct Vertex\n{\n    float3 pos : POSITION;\n    float2 uv  : TEXCOORD;\n    float4 color : COLOR;\n};\n\nstruct VSOutput\n{\n    float4 projPos : SV_POSITION;\n    float2 uv      : TEXCOORD;\n    float4 color   : COLOR;\n};\n\nstruct Constants\n{\n    float4x4 viewProj;\n};\nConstants k : register(c0);\n\nTexture2D<float4> tex : register(t0);\nSamplerState samp : register(s0);\n\nVSOutput vs(Vertex v)\n{\n    VSOutput o;\n    o.projPos = mul(float4(v.pos, 1), k.viewProj);\n    o.uv = v.uv;\n    o.color = v.color;\n    return o;\n}\n\nfloat4 ps(VSOutput input) : SV_TARGET\n{\n    return tex.Sample(samp, input.uv) * input.color;\n}"u8;
		TriangleFillShader.CompileShader(source, "vs"u8, "vs_5_0"u8, out var blob, "QuadBlitter VS");
		TriangleFillShader.CompileShader(source, "ps"u8, "ps_5_0"u8, out var blob2, "QuadBlitter 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 = 64u,
			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 = "POSITION"u8)
		{
			fixed (byte* semanticName2 = "TEXCOORD"u8)
			{
				fixed (byte* semanticName3 = "COLOR"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_R32G32_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;
				}
			}
		}
		D3D11_SAMPLER_DESC d3D11_SAMPLER_DESC = new D3D11_SAMPLER_DESC
		{
			Filter = D3D11_FILTER.D3D11_FILTER_MIN_MAG_MIP_LINEAR,
			AddressU = D3D11_TEXTURE_ADDRESS_MODE.D3D11_TEXTURE_ADDRESS_CLAMP,
			AddressV = D3D11_TEXTURE_ADDRESS_MODE.D3D11_TEXTURE_ADDRESS_CLAMP,
			AddressW = D3D11_TEXTURE_ADDRESS_MODE.D3D11_TEXTURE_ADDRESS_CLAMP,
			MaxAnisotropy = 1u,
			ComparisonFunc = D3D11_COMPARISON_FUNC.D3D11_COMPARISON_NEVER,
			MaxLOD = float.MaxValue
		};
		ID3D11SamplerState* sampler = default(ID3D11SamplerState*);
		Marshal.ThrowExceptionForHR(ctx.Device->CreateSamplerState(&d3D11_SAMPLER_DESC, &sampler));
		_sampler = sampler;
		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;
		}
		if (_sampler != null)
		{
			_sampler->Release();
			_sampler = 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);
		ID3D11SamplerState* sampler = _sampler;
		ctx.Context->PSSetSamplers(0u, 1u, &sampler);
		ctx.Context->GSSetShader(null, null, 0u);
	}

	public unsafe void Draw(FrameRenderContext ctx, Data data)
	{
		Bind(ctx);
		ID3D11Buffer* buffer = data.Buffer.Buffer;
		uint elementSize = (uint)data.Buffer.ElementSize;
		uint num = 0u;
		ctx.Context->IASetVertexBuffers(0u, 1u, &buffer, &elementSize, &num);
		foreach (DrawSegment segment in data._segments)
		{
			ID3D11ShaderResourceView* textureSRV = (ID3D11ShaderResourceView*)segment.TextureSRV;
			ctx.Context->PSSetShaderResources(0u, 1u, &textureSRV);
			ctx.Context->Draw((uint)segment.VertexCount, (uint)segment.StartVertex);
		}
		ID3D11ShaderResourceView* ptr = null;
		ctx.Context->PSSetShaderResources(0u, 1u, &ptr);
	}
}