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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)

{}

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

// 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");

        }

    }

}