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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() {}

// ------------------------------------------------------------------------------------------------
// 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 == 0) {
        return;
    }

    // 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];
            ai_assert(mat != nullptr);
            aiString name;
            mat->Get(AI_MATKEY_NAME,name);

            if (name.length != 0) {
                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) {
        delete [] aiMappingTable;
        delete [] aiHashes;
        pScene->mNumMaterials = 0;
        return;
    }
    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, AI_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.");
    }
}
