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/** @file RemoveRedundantMaterials.cpp
 *  @brief Implementation of the "RemoveRedundantMaterials" post processing step
*/

// internal headers

#include "RemoveRedundantMaterials.h"
#include <assimp/ParsingUtils.h>
#include "ProcessHelper.h"
#include "Material/MaterialSystem.h"
#include <assimp/Exceptional.h>
#include <stdio.h>

using namespace Assimp;

// ------------------------------------------------------------------------------------------------
// Constructor to be privately used by Importer
RemoveRedundantMatsProcess::RemoveRedundantMatsProcess()
: mConfigFixedMaterials() {
    // nothing to do here
}

// ------------------------------------------------------------------------------------------------
// Destructor, private as well
RemoveRedundantMatsProcess::~RemoveRedundantMatsProcess() = default;

// ------------------------------------------------------------------------------------------------
// Returns whether the processing step is present in the given flag field.
bool RemoveRedundantMatsProcess::IsActive( unsigned int pFlags) const
{
    return (pFlags & aiProcess_RemoveRedundantMaterials) != 0;
}

// ------------------------------------------------------------------------------------------------
// Setup import properties
void RemoveRedundantMatsProcess::SetupProperties(const Importer* pImp)
{
    // Get value of AI_CONFIG_PP_RRM_EXCLUDE_LIST
    mConfigFixedMaterials = pImp->GetPropertyString(AI_CONFIG_PP_RRM_EXCLUDE_LIST,"");
}

// ------------------------------------------------------------------------------------------------
// Executes the post processing step on the given imported data.
void RemoveRedundantMatsProcess::Execute( aiScene* pScene)
{
    ASSIMP_LOG_DEBUG("RemoveRedundantMatsProcess begin");

    unsigned int redundantRemoved = 0, unreferencedRemoved = 0;
    if (pScene->mNumMaterials)
    {
        // Find out which materials are referenced by meshes
        std::vector<bool> abReferenced(pScene->mNumMaterials,false);
        for (unsigned int i = 0;i < pScene->mNumMeshes;++i)
            abReferenced[pScene->mMeshes[i]->mMaterialIndex] = true;

        // If a list of materials to be excluded was given, match the list with
        // our imported materials and 'salt' all positive matches to ensure that
        // we get unique hashes later.
        if (mConfigFixedMaterials.length()) {

            std::list<std::string> strings;
            ConvertListToStrings(mConfigFixedMaterials,strings);

            for (unsigned int i = 0; i < pScene->mNumMaterials;++i) {
                aiMaterial* mat = pScene->mMaterials[i];

                aiString name;
                mat->Get(AI_MATKEY_NAME,name);

                if (name.length) {
                    std::list<std::string>::const_iterator it = std::find(strings.begin(), strings.end(), name.data);
                    if (it != strings.end()) {

                        // Our brilliant 'salt': A single material property with ~ as first
                        // character to mark it as internal and temporary.
                        const int dummy = 1;
                        ((aiMaterial*)mat)->AddProperty(&dummy,1,"~RRM.UniqueMaterial",0,0);

                        // Keep this material even if no mesh references it
                        abReferenced[i] = true;
                        ASSIMP_LOG_VERBOSE_DEBUG( "Found positive match in exclusion list: \'", name.data, "\'");
                    }
                }
            }
        }

        // TODO: re-implement this algorithm to work in-place
        unsigned int *aiMappingTable = new unsigned int[pScene->mNumMaterials];
        for ( unsigned int i=0; i<pScene->mNumMaterials; i++ ) {
            aiMappingTable[ i ] = 0;
        }
        unsigned int iNewNum = 0;

        // Iterate through all materials and calculate a hash for them
        // store all hashes in a list and so a quick search whether
        // we do already have a specific hash. This allows us to
        // determine which materials are identical.
        uint32_t *aiHashes = new uint32_t[ pScene->mNumMaterials ];;
        for (unsigned int i = 0; i < pScene->mNumMaterials;++i)
        {
            // No mesh is referencing this material, remove it.
            if (!abReferenced[i]) {
                ++unreferencedRemoved;
                delete pScene->mMaterials[i];
                pScene->mMaterials[i] = nullptr;
                continue;
            }

            // Check all previously mapped materials for a matching hash.
            // On a match we can delete this material and just make it ref to the same index.
            uint32_t me = aiHashes[i] = ComputeMaterialHash(pScene->mMaterials[i]);
            for (unsigned int a = 0; a < i;++a)
            {
                if (abReferenced[a] && me == aiHashes[a]) {
                    ++redundantRemoved;
                    me = 0;
                    aiMappingTable[i] = aiMappingTable[a];
                    delete pScene->mMaterials[i];
                    pScene->mMaterials[i] = nullptr;
                    break;
                }
            }
            // This is a new material that is referenced, add to the map.
            if (me) {
                aiMappingTable[i] = iNewNum++;
            }
        }
        // If the new material count differs from the original,
        // we need to rebuild the material list and remap mesh material indexes.
        if(iNewNum < 1)
          throw DeadlyImportError("No materials remaining");
        if (iNewNum != pScene->mNumMaterials) {
            ai_assert(iNewNum > 0);
            aiMaterial** ppcMaterials = new aiMaterial*[iNewNum];
            ::memset(ppcMaterials,0,sizeof(void*)*iNewNum);
            for (unsigned int p = 0; p < pScene->mNumMaterials;++p)
            {
                // if the material is not referenced ... remove it
                if (!abReferenced[p]) {
                    continue;
                }

                // generate new names for modified materials that had no names
                const unsigned int idx = aiMappingTable[p];
                if (ppcMaterials[idx]) {
                    aiString sz;
                    if( ppcMaterials[idx]->Get(AI_MATKEY_NAME, sz) != AI_SUCCESS ) {
                        sz.length = ::ai_snprintf(sz.data,MAXLEN,"JoinedMaterial_#%u",p);
                        ((aiMaterial*)ppcMaterials[idx])->AddProperty(&sz,AI_MATKEY_NAME);
                    }
                } else {
                    ppcMaterials[idx] = pScene->mMaterials[p];
                }
            }
            // update all material indices
            for (unsigned int p = 0; p < pScene->mNumMeshes;++p) {
                aiMesh* mesh = pScene->mMeshes[p];
                ai_assert(nullptr != mesh);
                mesh->mMaterialIndex = aiMappingTable[mesh->mMaterialIndex];
            }
            // delete the old material list
            delete[] pScene->mMaterials;
            pScene->mMaterials = ppcMaterials;
            pScene->mNumMaterials = iNewNum;
        }
        // delete temporary storage
        delete[] aiHashes;
        delete[] aiMappingTable;
    }
    if (redundantRemoved == 0 && unreferencedRemoved == 0)
    {
        ASSIMP_LOG_DEBUG("RemoveRedundantMatsProcess finished ");
    }
    else
    {
        ASSIMP_LOG_INFO("RemoveRedundantMatsProcess finished. Removed ", redundantRemoved, " redundant and ",
            unreferencedRemoved, " unused materials.");
    }
}
