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  ---------------------------------------------------------------------------
  Open Asset Import Library (assimp)
  ---------------------------------------------------------------------------
  
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    copyright notice, this list of conditions and the
    following disclaimer.
  
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    copyright notice, this list of conditions and the
    following disclaimer in the documentation and/or other
    materials provided with the distribution.
  
  * Neither the name of the assimp team, nor the names of its
    contributors may be used to endorse or promote products
    derived from this software without specific prior
    written permission of the assimp team.
  
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  OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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  */
  
  /** @file  FindInstancesProcess.cpp
   *  @brief Implementation of the aiProcess_FindInstances postprocessing step
  */
  
  
  #include "FindInstancesProcess.h"
  #include <memory>
  #include <stdio.h>
  
  using namespace Assimp;
  
  // ------------------------------------------------------------------------------------------------
  // Constructor to be privately used by Importer
  FindInstancesProcess::FindInstancesProcess()
  :   configSpeedFlag (false)
  {}
  
  // ------------------------------------------------------------------------------------------------
  // Destructor, private as well
  FindInstancesProcess::~FindInstancesProcess()
  {}
  
  // ------------------------------------------------------------------------------------------------
  // Returns whether the processing step is present in the given flag field.
  bool FindInstancesProcess::IsActive( unsigned int pFlags) const
  {
      // FindInstances makes absolutely no sense together with PreTransformVertices
      // fixme: spawn error message somewhere else?
      return 0 != (pFlags & aiProcess_FindInstances) && 0 == (pFlags & aiProcess_PreTransformVertices);
  }
  
  // ------------------------------------------------------------------------------------------------
  // Setup properties for the step
  void FindInstancesProcess::SetupProperties(const Importer* pImp)
  {
      // AI_CONFIG_FAVOUR_SPEED
      configSpeedFlag = (0 != pImp->GetPropertyInteger(AI_CONFIG_FAVOUR_SPEED,0));
  }
  
  // ------------------------------------------------------------------------------------------------
  // Compare the bones of two meshes
  bool CompareBones(const aiMesh* orig, const aiMesh* inst)
  {
      for (unsigned int i = 0; i < orig->mNumBones;++i) {
          aiBone* aha = orig->mBones[i];
          aiBone* oha = inst->mBones[i];
  
          if (aha->mNumWeights   != oha->mNumWeights   ||
              aha->mOffsetMatrix != oha->mOffsetMatrix) {
              return false;
          }
  
          // compare weight per weight ---
          for (unsigned int n = 0; n < aha->mNumWeights;++n) {
              if  (aha->mWeights[n].mVertexId != oha->mWeights[n].mVertexId ||
                  (aha->mWeights[n].mWeight - oha->mWeights[n].mWeight) < 10e-3f) {
                  return false;
              }
          }
      }
      return true;
  }
  
  // ------------------------------------------------------------------------------------------------
  // Update mesh indices in the node graph
  void UpdateMeshIndices(aiNode* node, unsigned int* lookup)
  {
      for (unsigned int n = 0; n < node->mNumMeshes;++n)
          node->mMeshes[n] = lookup[node->mMeshes[n]];
  
      for (unsigned int n = 0; n < node->mNumChildren;++n)
          UpdateMeshIndices(node->mChildren[n],lookup);
  }
  
  // ------------------------------------------------------------------------------------------------
  // Executes the post processing step on the given imported data.
  void FindInstancesProcess::Execute( aiScene* pScene)
  {
      ASSIMP_LOG_DEBUG("FindInstancesProcess begin");
      if (pScene->mNumMeshes) {
  
          // use a pseudo hash for all meshes in the scene to quickly find
          // the ones which are possibly equal. This step is executed early
          // in the pipeline, so we could, depending on the file format,
          // have several thousand small meshes. That's too much for a brute
          // everyone-against-everyone check involving up to 10 comparisons
          // each.
          std::unique_ptr<uint64_t[]> hashes (new uint64_t[pScene->mNumMeshes]);
          std::unique_ptr<unsigned int[]> remapping (new unsigned int[pScene->mNumMeshes]);
  
          unsigned int numMeshesOut = 0;
          for (unsigned int i = 0; i < pScene->mNumMeshes; ++i) {
  
              aiMesh* inst = pScene->mMeshes[i];
              hashes[i] = GetMeshHash(inst);
  
              // Find an appropriate epsilon
              // to compare position differences against
              float epsilon = ComputePositionEpsilon(inst);
              epsilon *= epsilon;
  
              for (int a = i-1; a >= 0; --a) {
                  if (hashes[i] == hashes[a])
                  {
                      aiMesh* orig = pScene->mMeshes[a];
                      if (!orig)
                          continue;
  
                      // check for hash collision .. we needn't check
                      // the vertex format, it *must* match due to the
                      // (brilliant) construction of the hash
                      if (orig->mNumBones       != inst->mNumBones      ||
                          orig->mNumFaces       != inst->mNumFaces      ||
                          orig->mNumVertices    != inst->mNumVertices   ||
                          orig->mMaterialIndex  != inst->mMaterialIndex ||
                          orig->mPrimitiveTypes != inst->mPrimitiveTypes)
                          continue;
  
                      // up to now the meshes are equal. Now compare vertex positions, normals,
                      // tangents and bitangents using this epsilon.
                      if (orig->HasPositions()) {
                          if(!CompareArrays(orig->mVertices,inst->mVertices,orig->mNumVertices,epsilon))
                              continue;
                      }
                      if (orig->HasNormals()) {
                          if(!CompareArrays(orig->mNormals,inst->mNormals,orig->mNumVertices,epsilon))
                              continue;
                      }
                      if (orig->HasTangentsAndBitangents()) {
                          if (!CompareArrays(orig->mTangents,inst->mTangents,orig->mNumVertices,epsilon) ||
                              !CompareArrays(orig->mBitangents,inst->mBitangents,orig->mNumVertices,epsilon))
                              continue;
                      }
  
                      // use a constant epsilon for colors and UV coordinates
                      static const float uvEpsilon = 10e-4f;
                      {
                          unsigned int j, end = orig->GetNumUVChannels();
                          for(j = 0; j < end; ++j) {
                              if (!orig->mTextureCoords[j]) {
                                  continue;
                              }
                              if(!CompareArrays(orig->mTextureCoords[j],inst->mTextureCoords[j],orig->mNumVertices,uvEpsilon)) {
                                  break;
                              }
                          }
                          if (j != end) {
                              continue;
                          }
                      }
                      {
                          unsigned int j, end = orig->GetNumColorChannels();
                          for(j = 0; j < end; ++j) {
                              if (!orig->mColors[j]) {
                                  continue;
                              }
                              if(!CompareArrays(orig->mColors[j],inst->mColors[j],orig->mNumVertices,uvEpsilon)) {
                                  break;
                              }
                          }
                          if (j != end) {
                              continue;
                          }
                      }
  
                      // These two checks are actually quite expensive and almost *never* required.
                      // Almost. That's why they're still here. But there's no reason to do them
                      // in speed-targeted imports.
                      if (!configSpeedFlag) {
  
                          // It seems to be strange, but we really need to check whether the
                          // bones are identical too. Although it's extremely unprobable
                          // that they're not if control reaches here, we need to deal
                          // with unprobable cases, too. It could still be that there are
                          // equal shapes which are deformed differently.
                          if (!CompareBones(orig,inst))
                              continue;
  
                          // For completeness ... compare even the index buffers for equality
                          // face order & winding order doesn't care. Input data is in verbose format.
                          std::unique_ptr<unsigned int[]> ftbl_orig(new unsigned int[orig->mNumVertices]);
                          std::unique_ptr<unsigned int[]> ftbl_inst(new unsigned int[orig->mNumVertices]);
  
                          for (unsigned int tt = 0; tt < orig->mNumFaces;++tt) {
                              aiFace& f = orig->mFaces[tt];
                              for (unsigned int nn = 0; nn < f.mNumIndices;++nn)
                                  ftbl_orig[f.mIndices[nn]] = tt;
  
                              aiFace& f2 = inst->mFaces[tt];
                              for (unsigned int nn = 0; nn < f2.mNumIndices;++nn)
                                  ftbl_inst[f2.mIndices[nn]] = tt;
                          }
                          if (0 != ::memcmp(ftbl_inst.get(),ftbl_orig.get(),orig->mNumVertices*sizeof(unsigned int)))
                              continue;
                      }
  
                      // We're still here. Or in other words: 'inst' is an instance of 'orig'.
                      // Place a marker in our list that we can easily update mesh indices.
                      remapping[i] = remapping[a];
  
                      // Delete the instanced mesh, we don't need it anymore
                      delete inst;
                      pScene->mMeshes[i] = nullptr;
                      break;
                  }
              }
  
              // If we didn't find a match for the current mesh: keep it
              if (pScene->mMeshes[i]) {
                  remapping[i] = numMeshesOut++;
              }
          }
          ai_assert(0 != numMeshesOut);
          if (numMeshesOut != pScene->mNumMeshes) {
  
              // Collapse the meshes array by removing all nullptr entries
              for (unsigned int real = 0, i = 0; real < numMeshesOut; ++i) {
                  if (pScene->mMeshes[i])
                      pScene->mMeshes[real++] = pScene->mMeshes[i];
              }
  
              // And update the node graph with our nice lookup table
              UpdateMeshIndices(pScene->mRootNode,remapping.get());
  
              // write to log
              if (!DefaultLogger::isNullLogger()) {
                  ASSIMP_LOG_INFO( "FindInstancesProcess finished. Found ", (pScene->mNumMeshes - numMeshesOut), " instances" );
              }
              pScene->mNumMeshes = numMeshesOut;
          } else {
              ASSIMP_LOG_DEBUG("FindInstancesProcess finished. No instanced meshes found");
          }
      }
  }
  