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  #pragma once
  #include "Falcor.h"
  
  using namespace Falcor;
  
  /** Temporal accumulation render pass.
  
      This pass takes a texture as input and writes the temporally accumulated
      result to an output texture. The pass keeps intermediate data internally.
  
      For accumulating many samples for ground truth rendering etc., fp32 precision
      is not always sufficient. The pass supports higher precision modes using
      either error compensation (Kahan summation) or double precision math.
  */
  class AccumulatePass : public RenderPass
  {
  public:
      using SharedPtr = std::shared_ptr<AccumulatePass>;
  
      virtual ~AccumulatePass() = default;
  
      static SharedPtr create(RenderContext* pRenderContext = nullptr, const Dictionary& dict = {});
  
      virtual std::string getDesc() override { return "Temporal accumulation pass"; }
      virtual Dictionary getScriptingDictionary() override;
      virtual RenderPassReflection reflect(const CompileData& compileData) override;
      virtual void compile(RenderContext* pContext, const CompileData& compileData) override;
      virtual void execute(RenderContext* pRenderContext, const RenderData& renderData) override;
      virtual void renderUI(Gui::Widgets& widget) override;
      virtual void setScene(RenderContext* pRenderContext, const Scene::SharedPtr& pScene) override;
      virtual bool onMouseEvent(const MouseEvent& mouseEvent) override { return false; }
      virtual bool onKeyEvent(const KeyboardEvent& keyEvent) override { return false; }
      virtual void onHotReload(HotReloadFlags reloaded) override;
      virtual void updateDict(const Dictionary& dict) override;
  
      // Scripting functions
      void reset() { mFrameCount = 0; }
  
      enum class Precision : uint32_t
      {
          Double,                 ///< Standard summation in double precision.
          Single,                 ///< Standard summation in single precision.
          SingleCompensated,      ///< Compensated summation (Kahan summation) in single precision.
      };
  
  protected:
      AccumulatePass(const Dictionary& dict);
      void prepareAccumulation(RenderContext* pRenderContext, uint32_t width, uint32_t height);
  
      // Internal state
      Scene::SharedPtr            mpScene;                        ///< The current scene (or nullptr if no scene).
      std::map<Precision, ComputeProgram::SharedPtr> mpProgram;   ///< Accumulation programs, one per mode.
      ComputeVars::SharedPtr      mpVars;                         ///< Program variables.
      ComputeState::SharedPtr     mpState;
  
      uint32_t                    mFrameCount = 0;                ///< Number of accumulated frames. This is reset upon changes.
      uint2                       mFrameDim = { 0, 0 };           ///< Current frame dimension in pixels.
      Texture::SharedPtr          mpLastFrameSum;                 ///< Last frame running sum. Used in Single and SingleKahan mode.
      Texture::SharedPtr          mpLastFrameCorr;                ///< Last frame running compensation term. Used in SingleKahan mode.
      Texture::SharedPtr          mpLastFrameSumLo;               ///< Last frame running sum (lo bits). Used in Double mode.
      Texture::SharedPtr          mpLastFrameSumHi;               ///< Last frame running sum (hi bits). Used in Double mode.
  
      // UI variables
      bool                        mEnableAccumulation = true;     ///< UI control if accumulation is enabled.
      bool                        mAutoReset = true;              ///< Reset accumulation automatically upon scene changes, refresh flags, and/or subframe count.
      Precision                   mPrecisionMode = Precision::Double;
      uint32_t                    mSubFrameCount = 0;             ///< Number of frames to accumulate before reset. Useful for generating references.
  };
  