using System;
using System.Runtime.InteropServices;
using UnityEngine;
using UnityEngine.Profiling;
using UnityEngine.Rendering;

namespace FidelityFX.OpticalFlow
{
    internal abstract class OpticalFlowPass: IDisposable
    {
        protected readonly OpticalFlow.ContextDescription ContextDescription;
        protected readonly OpticalFlowResources Resources;
        protected readonly ComputeBuffer Constants;
        
        protected ComputeShader ComputeShader;
        protected int KernelIndex;
        
        private CustomSampler _sampler;
        
        protected OpticalFlowPass(OpticalFlow.ContextDescription contextDescription, OpticalFlowResources resources, ComputeBuffer constants)
        {
            ContextDescription = contextDescription;
            Resources = resources;
            Constants = constants;
        }

        public virtual void Dispose()
        {
        }
        
        public void ScheduleDispatch(CommandBuffer commandBuffer, OpticalFlow.DispatchDescription dispatchParams, int frameIndex, int dispatchX, int dispatchY, int dispatchZ = 1)
        {
            commandBuffer.BeginSample(_sampler);
            DoScheduleDispatch(commandBuffer, dispatchParams, frameIndex, dispatchX, dispatchY, dispatchZ);
            commandBuffer.EndSample(_sampler);
        }

        protected abstract void DoScheduleDispatch(CommandBuffer commandBuffer, OpticalFlow.DispatchDescription dispatchParams, int frameIndex, int dispatchX, int dispatchY, int dispatchZ);

        protected void InitComputeShader(string passName, ComputeShader shader)
        {
            if (shader == null)
            {
                throw new MissingReferenceException($"Shader for Optical Flow pass '{passName}' could not be loaded! Please ensure it is included in the project correctly.");
            }

            ComputeShader = shader;
            KernelIndex = ComputeShader.FindKernel("CS");
            _sampler = CustomSampler.Create(passName);
        }
    }

    internal class OpticalFlowPrepareLumaPass : OpticalFlowPass
    {
        public OpticalFlowPrepareLumaPass(OpticalFlow.ContextDescription contextDescription, OpticalFlowResources resources, ComputeBuffer constants) 
            : base(contextDescription, resources, constants)
        {
            InitComputeShader("Prepare Luma", contextDescription.shaders.prepareLuma);
        }

        protected override void DoScheduleDispatch(CommandBuffer commandBuffer, OpticalFlow.DispatchDescription dispatchParams, int frameIndex, int dispatchX, int dispatchY, int dispatchZ)
        {
            ref var color = ref dispatchParams.color;
            commandBuffer.SetComputeTextureParam(ComputeShader, KernelIndex, OpticalFlowShaderIDs.SrvInputColor, color.RenderTarget, color.MipLevel, color.SubElement);

            commandBuffer.SetComputeTextureParam(ComputeShader, KernelIndex, OpticalFlowShaderIDs.UavOpticalFlowInput, Resources.OpticalFlowInputLevels[0][frameIndex]);
            
            commandBuffer.SetComputeConstantBufferParam(ComputeShader, OpticalFlowShaderIDs.CbOpticalFlow, Constants, 0, Marshal.SizeOf<OpticalFlow.OpticalFlowConstants>());
            
            commandBuffer.DispatchCompute(ComputeShader, KernelIndex, dispatchX, dispatchY, dispatchZ);
        }
    }

    internal class OpticalFlowGenerateInputPyramidPass : OpticalFlowPass
    {
        private ComputeBuffer _spdConstants;
        
        public OpticalFlowGenerateInputPyramidPass(OpticalFlow.ContextDescription contextDescription, OpticalFlowResources resources, ComputeBuffer constants, ComputeBuffer spdConstants) 
            : base(contextDescription, resources, constants)
        {
            _spdConstants = spdConstants;
            InitComputeShader("Generate Optical Flow Input Pyramid", contextDescription.shaders.generateOpticalFlowInputPyramid);
        }

        protected override void DoScheduleDispatch(CommandBuffer commandBuffer, OpticalFlow.DispatchDescription dispatchParams, int frameIndex, int dispatchX, int dispatchY, int dispatchZ)
        {
            commandBuffer.SetComputeTextureParam(ComputeShader, KernelIndex, OpticalFlowShaderIDs.UavOpticalFlowInput, Resources.OpticalFlowInputLevels[0][frameIndex]);
            commandBuffer.SetComputeTextureParam(ComputeShader, KernelIndex, OpticalFlowShaderIDs.UavOpticalFlowInputLevel1, Resources.OpticalFlowInputLevels[1][frameIndex]);
            commandBuffer.SetComputeTextureParam(ComputeShader, KernelIndex, OpticalFlowShaderIDs.UavOpticalFlowInputLevel2, Resources.OpticalFlowInputLevels[2][frameIndex]);
            commandBuffer.SetComputeTextureParam(ComputeShader, KernelIndex, OpticalFlowShaderIDs.UavOpticalFlowInputLevel3, Resources.OpticalFlowInputLevels[3][frameIndex]);
            commandBuffer.SetComputeTextureParam(ComputeShader, KernelIndex, OpticalFlowShaderIDs.UavOpticalFlowInputLevel4, Resources.OpticalFlowInputLevels[4][frameIndex]);
            commandBuffer.SetComputeTextureParam(ComputeShader, KernelIndex, OpticalFlowShaderIDs.UavOpticalFlowInputLevel5, Resources.OpticalFlowInputLevels[5][frameIndex]);
            commandBuffer.SetComputeTextureParam(ComputeShader, KernelIndex, OpticalFlowShaderIDs.UavOpticalFlowInputLevel6, Resources.OpticalFlowInputLevels[6][frameIndex]);
            
            commandBuffer.SetComputeConstantBufferParam(ComputeShader, OpticalFlowShaderIDs.CbOpticalFlow, Constants, 0, Marshal.SizeOf<OpticalFlow.OpticalFlowConstants>());
            commandBuffer.SetComputeConstantBufferParam(ComputeShader, OpticalFlowShaderIDs.CbSpd, _spdConstants, 0, Marshal.SizeOf<OpticalFlow.SpdConstants>());
            
            commandBuffer.DispatchCompute(ComputeShader, KernelIndex, dispatchX, dispatchY, dispatchZ);
        }
    }

    internal class OpticalFlowGenerateSCDHistogramPass : OpticalFlowPass
    {
        public OpticalFlowGenerateSCDHistogramPass(OpticalFlow.ContextDescription contextDescription, OpticalFlowResources resources, ComputeBuffer constants) 
            : base(contextDescription, resources, constants)
        {
            InitComputeShader("Generate SCD Histogram", contextDescription.shaders.generateScdHistogram);
        }

        protected override void DoScheduleDispatch(CommandBuffer commandBuffer, OpticalFlow.DispatchDescription dispatchParams, int frameIndex, int dispatchX, int dispatchY, int dispatchZ)
        {
            // TODO: probably needs to be input from this frame (result from previous passes), but double check to be sure
            commandBuffer.SetComputeTextureParam(ComputeShader, KernelIndex, OpticalFlowShaderIDs.SrvOpticalFlowInput, Resources.OpticalFlowInputLevels[0][frameIndex]);
            commandBuffer.SetComputeTextureParam(ComputeShader, KernelIndex, OpticalFlowShaderIDs.UavOpticalFlowScdHistogram, Resources.OpticalFlowSCDHistogram);
            
            commandBuffer.SetComputeConstantBufferParam(ComputeShader, OpticalFlowShaderIDs.CbOpticalFlow, Constants, 0, Marshal.SizeOf<OpticalFlow.OpticalFlowConstants>());
            
            commandBuffer.DispatchCompute(ComputeShader, KernelIndex, dispatchX, dispatchY, dispatchZ);
        }
    }

    internal class OpticalFlowComputeSCDDivergencePass : OpticalFlowPass
    {
        public OpticalFlowComputeSCDDivergencePass(OpticalFlow.ContextDescription contextDescription, OpticalFlowResources resources, ComputeBuffer constants) 
            : base(contextDescription, resources, constants)
        {
            InitComputeShader("Compute SCD Divergence", contextDescription.shaders.computeScdDivergence);
        }

        protected override void DoScheduleDispatch(CommandBuffer commandBuffer, OpticalFlow.DispatchDescription dispatchParams, int frameIndex, int dispatchX, int dispatchY, int dispatchZ)
        {
            ref var scdOutput = ref dispatchParams.opticalFlowSCD;
            
            commandBuffer.SetComputeTextureParam(ComputeShader, KernelIndex, OpticalFlowShaderIDs.UavOpticalFlowScdHistogram, Resources.OpticalFlowSCDHistogram);
            commandBuffer.SetComputeTextureParam(ComputeShader, KernelIndex, OpticalFlowShaderIDs.UavOpticalFlowScdPreviousHistogram, Resources.OpticalFlowSCDPreviousHistogram);
            commandBuffer.SetComputeTextureParam(ComputeShader, KernelIndex, OpticalFlowShaderIDs.UavOpticalFlowScdTemp, Resources.OpticalFlowSCDTemp);
            commandBuffer.SetComputeTextureParam(ComputeShader, KernelIndex, OpticalFlowShaderIDs.UavOpticalFlowScdOutput, scdOutput.RenderTarget, scdOutput.MipLevel, scdOutput.SubElement);
            
            commandBuffer.SetComputeConstantBufferParam(ComputeShader, OpticalFlowShaderIDs.CbOpticalFlow, Constants, 0, Marshal.SizeOf<OpticalFlow.OpticalFlowConstants>());
            
            commandBuffer.DispatchCompute(ComputeShader, KernelIndex, dispatchX, dispatchY, dispatchZ);
        }
    }

    internal class OpticalFlowComputePass : OpticalFlowPass
    {
        public OpticalFlowComputePass(OpticalFlow.ContextDescription contextDescription, OpticalFlowResources resources, ComputeBuffer constants) 
            : base(contextDescription, resources, constants)
        {
        }

        protected override void DoScheduleDispatch(CommandBuffer commandBuffer, OpticalFlow.DispatchDescription dispatchParams, int frameIndex, int dispatchX, int dispatchY, int dispatchZ)
        {
            throw new NotImplementedException();
        }
    }

    internal class OpticalFlowFilterPass : OpticalFlowPass
    {
        public OpticalFlowFilterPass(OpticalFlow.ContextDescription contextDescription, OpticalFlowResources resources, ComputeBuffer constants)
            : base(contextDescription, resources, constants)
        {
        }

        protected override void DoScheduleDispatch(CommandBuffer commandBuffer, OpticalFlow.DispatchDescription dispatchParams, int frameIndex, int dispatchX, int dispatchY, int dispatchZ)
        {
            throw new NotImplementedException();
        }
    }

    internal class OpticalFlowScalePass : OpticalFlowPass
    {
        public OpticalFlowScalePass(OpticalFlow.ContextDescription contextDescription, OpticalFlowResources resources, ComputeBuffer constants) 
            : base(contextDescription, resources, constants)
        {
        }

        protected override void DoScheduleDispatch(CommandBuffer commandBuffer, OpticalFlow.DispatchDescription dispatchParams, int frameIndex, int dispatchX, int dispatchY, int dispatchZ)
        {
            throw new NotImplementedException();
        }
    }
}