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/** @file  OptimizeGraph.cpp

 *  @brief Implementation of the aiProcess_OptimizGraph step

 */

#ifndef ASSIMP_BUILD_NO_OPTIMIZEGRAPH_PROCESS

#include "OptimizeGraph.h"

#include "ProcessHelper.h"

#include "ConvertToLHProcess.h"

#include <assimp/Exceptional.h>

#include <assimp/SceneCombiner.h>

#include <stdio.h>

using namespace Assimp;

#define AI_RESERVED_NODE_NAME "$Reserved_And_Evil"

/* AI_OG_USE_HASHING enables the use of hashing to speed-up std::set lookups.

 * The unhashed variant should be faster, except for *very* large data sets

 */

#ifdef AI_OG_USE_HASHING

// Use our standard hashing function to compute the hash

#define AI_OG_GETKEY(str) SuperFastHash(str.data, str.length)

#else

// Otherwise hope that std::string will utilize a static buffer

// for shorter node names. This would avoid endless heap copying.

#define AI_OG_GETKEY(str) std::string(str.data)

#endif

// ------------------------------------------------------------------------------------------------

// Constructor to be privately used by Importer

OptimizeGraphProcess::OptimizeGraphProcess() :

    mScene(),

    nodes_in(),

    nodes_out(),

    count_merged() {

  // empty

}

// ------------------------------------------------------------------------------------------------

// Returns whether the processing step is present in the given flag field.

bool OptimizeGraphProcess::IsActive(unsigned int pFlags) const {

  return (0 != (pFlags & aiProcess_OptimizeGraph));

}

// ------------------------------------------------------------------------------------------------

// Setup properties for the post-processing step

void OptimizeGraphProcess::SetupProperties(const Importer *pImp) {

  // Get value of AI_CONFIG_PP_OG_EXCLUDE_LIST

  std::string tmp = pImp->GetPropertyString(AI_CONFIG_PP_OG_EXCLUDE_LIST, "");

  AddLockedNodeList(tmp);

}

// ------------------------------------------------------------------------------------------------

// Collect new children

void OptimizeGraphProcess::CollectNewChildren(aiNode *nd, std::list<aiNode *> &nodes) {

  nodes_in += nd->mNumChildren;

  // Process children

  std::list<aiNode *> child_nodes;

  for (unsigned int i = 0; i < nd->mNumChildren; ++i) {

    CollectNewChildren(nd->mChildren[i], child_nodes);

    nd->mChildren[i] = nullptr;

  }

  // Check whether we need this node; if not we can replace it by our own children (warn, danger of incest).

  if (locked.find(AI_OG_GETKEY(nd->mName)) == locked.end()) {

    for (std::list<aiNode *>::iterator it = child_nodes.begin(); it != child_nodes.end();) {

      if (locked.find(AI_OG_GETKEY((*it)->mName)) == locked.end()) {

        (*it)->mTransformation = nd->mTransformation * (*it)->mTransformation;

        nodes.push_back(*it);

        it = child_nodes.erase(it);

        continue;

      }

      ++it;

    }

    if (nd->mNumMeshes || !child_nodes.empty()) {

      nodes.push_back(nd);

    } else {

      delete nd; /* bye, node */

      return;

    }

  } else {

    // Retain our current position in the hierarchy

    nodes.push_back(nd);

    // Now check for possible optimizations in our list of child nodes. join as many as possible

    aiNode *join_master = nullptr;

    aiMatrix4x4 inv;

    const LockedSetType::const_iterator end = locked.end();

    std::list<aiNode *> join;

    for (std::list<aiNode *>::iterator it = child_nodes.begin(); it != child_nodes.end();) {

      aiNode *child = *it;

      if (child->mNumChildren == 0 && locked.find(AI_OG_GETKEY(child->mName)) == end) {

        // There may be no instanced meshes

        unsigned int n = 0;

        for (; n < child->mNumMeshes; ++n) {

          if (meshes[child->mMeshes[n]] > 1) {

            break;

          }

        }

        if (n == child->mNumMeshes) {

          if (!join_master) {

            join_master = child;

            inv = join_master->mTransformation;

            inv.Inverse();

          } else {

            child->mTransformation = inv * child->mTransformation;

            join.push_back(child);

            it = child_nodes.erase(it);

            continue;

          }

        }

      }

      ++it;

    }

    if (join_master && !join.empty()) {

            join_master->mName.length = ::ai_snprintf(join_master->mName.data, AI_MAXLEN, "$MergedNode_%u", count_merged++);

      unsigned int out_meshes = 0;

      for (std::list<aiNode *>::const_iterator it = join.cbegin(); it != join.cend(); ++it) {

        out_meshes += (*it)->mNumMeshes;

      }

      // copy all mesh references in one array

      if (out_meshes) {

        unsigned int *meshIdxs = new unsigned int[out_meshes + join_master->mNumMeshes], *tmp = meshIdxs;

        for (unsigned int n = 0; n < join_master->mNumMeshes; ++n) {

          *tmp++ = join_master->mMeshes[n];

        }

        for (const aiNode *join_node : join) {

          for (unsigned int n = 0; n < join_node->mNumMeshes; ++n) {

            *tmp = join_node->mMeshes[n];

            aiMesh *mesh = mScene->mMeshes[*tmp++];

            // Assume the transformation is affine

            // manually move the mesh into the right coordinate system

            // Check for odd negative scale (mirror)

            if (join_node->mTransformation.Determinant() < 0) {

              // Reverse the mesh face winding order

                            FlipWindingOrderProcess::ProcessMesh(mesh);

            }

                        // Update positions, normals and tangents

            const aiMatrix3x3 IT = aiMatrix3x3(join_node->mTransformation).Inverse().Transpose();

            for (unsigned int a = 0; a < mesh->mNumVertices; ++a) {

              mesh->mVertices[a] *= join_node->mTransformation;

              if (mesh->HasNormals())

                mesh->mNormals[a] *= IT;

              if (mesh->HasTangentsAndBitangents()) {

                mesh->mTangents[a] *= IT;

                mesh->mBitangents[a] *= IT;

              }

            }

          }

          delete join_node; // bye, node

        }

        delete[] join_master->mMeshes;

        join_master->mMeshes = meshIdxs;

        join_master->mNumMeshes += out_meshes;

      }

    }

  }

  // reassign children if something changed

  if (child_nodes.empty() || child_nodes.size() > nd->mNumChildren) {

    delete[] nd->mChildren;

    if (!child_nodes.empty()) {

      nd->mChildren = new aiNode *[child_nodes.size()];

    } else

      nd->mChildren = nullptr;

  }

  nd->mNumChildren = static_cast<unsigned int>(child_nodes.size());

  if (nd->mChildren) {

    aiNode **tmp = nd->mChildren;

    for (std::list<aiNode *>::iterator it = child_nodes.begin(); it != child_nodes.end(); ++it) {

      aiNode *node = *tmp++ = *it;

      node->mParent = nd;

    }

  }

  nodes_out += static_cast<unsigned int>(child_nodes.size());

}

// ------------------------------------------------------------------------------------------------

// Execute the post-processing step on the given scene

void OptimizeGraphProcess::Execute(aiScene *pScene) {

  ASSIMP_LOG_DEBUG("OptimizeGraphProcess begin");

  nodes_in = nodes_out = count_merged = 0;

  mScene = pScene;

  meshes.resize(pScene->mNumMeshes, 0);

  FindInstancedMeshes(pScene->mRootNode);

  // build a blacklist of identifiers. If the name of a node matches one of these, we won't touch it

  locked.clear();

  for (std::list<std::string>::const_iterator it = locked_nodes.begin(); it != locked_nodes.end(); ++it) {

#ifdef AI_OG_USE_HASHING

    locked.insert(SuperFastHash((*it).c_str()));

#else

    locked.insert(*it);

#endif

  }

  for (unsigned int i = 0; i < pScene->mNumAnimations; ++i) {

    for (unsigned int a = 0; a < pScene->mAnimations[i]->mNumChannels; ++a) {

      aiNodeAnim *anim = pScene->mAnimations[i]->mChannels[a];

      locked.insert(AI_OG_GETKEY(anim->mNodeName));

    }

  }

  for (unsigned int i = 0; i < pScene->mNumMeshes; ++i) {

    for (unsigned int a = 0; a < pScene->mMeshes[i]->mNumBones; ++a) {

      aiBone *bone = pScene->mMeshes[i]->mBones[a];

      locked.insert(AI_OG_GETKEY(bone->mName));

      // HACK: Meshes referencing bones may not be transformed; we need to look them.

      // The easiest way to do this is to increase their reference counters ...

      meshes[i] += 2;

    }

  }

  for (unsigned int i = 0; i < pScene->mNumCameras; ++i) {

    aiCamera *cam = pScene->mCameras[i];

    locked.insert(AI_OG_GETKEY(cam->mName));

  }

  for (unsigned int i = 0; i < pScene->mNumLights; ++i) {

    aiLight *lgh = pScene->mLights[i];

    locked.insert(AI_OG_GETKEY(lgh->mName));

  }

  // Insert a dummy master node and make it read-only

  aiNode *dummy_root = new aiNode(AI_RESERVED_NODE_NAME);

  locked.insert(AI_OG_GETKEY(dummy_root->mName));

  const aiString prev = pScene->mRootNode->mName;

  pScene->mRootNode->mParent = dummy_root;

  dummy_root->mChildren = new aiNode *[dummy_root->mNumChildren = 1];

  dummy_root->mChildren[0] = pScene->mRootNode;

  // Do our recursive processing of scenegraph nodes. For each node collect

  // a fully new list of children and allow their children to place themselves

  // on the same hierarchy layer as their parents.

  std::list<aiNode *> nodes;

  CollectNewChildren(dummy_root, nodes);

  ai_assert(nodes.size() == 1);

  if (dummy_root->mNumChildren == 0) {

    pScene->mRootNode = nullptr;

    throw DeadlyImportError("After optimizing the scene graph, no data remains");

  }

  if (dummy_root->mNumChildren > 1) {

    pScene->mRootNode = dummy_root;

    // Keep the dummy node but assign the name of the old root node to it

    pScene->mRootNode->mName = prev;

  } else {

    // Remove the dummy root node again.

    pScene->mRootNode = dummy_root->mChildren[0];

    dummy_root->mChildren[0] = nullptr;

    delete dummy_root;

  }

  pScene->mRootNode->mParent = nullptr;

  if (!DefaultLogger::isNullLogger()) {

    if (nodes_in != nodes_out) {

      ASSIMP_LOG_INFO("OptimizeGraphProcess finished; Input nodes: ", nodes_in, ", Output nodes: ", nodes_out);

    } else {

      ASSIMP_LOG_DEBUG("OptimizeGraphProcess finished");

    }

  }

  meshes.clear();

  locked.clear();

}

// ------------------------------------------------------------------------------------------------

// Build a LUT of all instanced meshes

void OptimizeGraphProcess::FindInstancedMeshes(aiNode *pNode) {

  for (unsigned int i = 0; i < pNode->mNumMeshes; ++i) {

    ++meshes[pNode->mMeshes[i]];

  }

  for (unsigned int i = 0; i < pNode->mNumChildren; ++i)

    FindInstancedMeshes(pNode->mChildren[i]);

}

#endif // !! ASSIMP_BUILD_NO_OPTIMIZEGRAPH_PROCESS