/*
Open Asset Import Library (ASSIMP)
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*/

/** Implementation of the LimitBoneWeightsProcess post processing step */

#include "AssimpPCH.h"
#include "LimitBoneWeightsProcess.h"


using namespace Assimp;


// ------------------------------------------------------------------------------------------------
// Constructor to be privately used by Importer
LimitBoneWeightsProcess::LimitBoneWeightsProcess()
{
	mMaxWeights = AI_LMW_MAX_WEIGHTS;
}

// ------------------------------------------------------------------------------------------------
// Destructor, private as well
LimitBoneWeightsProcess::~LimitBoneWeightsProcess()
{
	// nothing to do here
}

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

// ------------------------------------------------------------------------------------------------
// Executes the post processing step on the given imported data.
void LimitBoneWeightsProcess::Execute( aiScene* pScene)
{
	for( unsigned int a = 0; a < pScene->mNumMeshes; a++)
		ProcessMesh( pScene->mMeshes[a]);
}

// ------------------------------------------------------------------------------------------------
// Executes the post processing step on the given imported data.
void LimitBoneWeightsProcess::SetupProperties(const Importer* pImp)
{
	// get the current value of the property
	this->mMaxWeights = pImp->GetPropertyInteger(AI_CONFIG_PP_LBW_MAX_WEIGHTS,AI_LMW_MAX_WEIGHTS);
}

// ------------------------------------------------------------------------------------------------
// Unites identical vertices in the given mesh
void LimitBoneWeightsProcess::ProcessMesh( aiMesh* pMesh)
{
	if( !pMesh->HasBones())
		return;

	// collect all bone weights per vertex
	typedef std::vector< std::vector< Weight > > WeightsPerVertex;
	WeightsPerVertex vertexWeights( pMesh->mNumVertices);

	// collect all weights per vertex
	for( unsigned int a = 0; a < pMesh->mNumBones; a++)
	{
		const aiBone* bone = pMesh->mBones[a];
		for( unsigned int b = 0; b < bone->mNumWeights; b++)
		{
			const aiVertexWeight& w = bone->mWeights[b];
			vertexWeights[w.mVertexId].push_back( Weight( a, w.mWeight));
		}
	}

	// now cut the weight count if it exceeds the maximum
	bool bChanged = false;
	for( WeightsPerVertex::iterator vit = vertexWeights.begin(); vit != vertexWeights.end(); ++vit)
	{
		if( vit->size() <= mMaxWeights)
			continue;

		bChanged = true;

		// more than the defined maximum -> first sort by weight in descending order. That's 
		// why we defined the < operator in such a weird way.
		std::sort( vit->begin(), vit->end());

		// now kill everything beyond the maximum count
		vit->erase( vit->begin() + mMaxWeights, vit->end());

		// and renormalize the weights
		float sum = 0.0f;
		for( std::vector<Weight>::const_iterator it = vit->begin(); it != vit->end(); ++it)
			sum += it->mWeight;
		for( std::vector<Weight>::iterator it = vit->begin(); it != vit->end(); ++it)
			it->mWeight /= sum;
	}

	if (bChanged)
	{

		// rebuild the vertex weight array for all bones 
		typedef std::vector< std::vector< aiVertexWeight > > WeightsPerBone;
		WeightsPerBone boneWeights( pMesh->mNumBones);
		for( unsigned int a = 0; a < vertexWeights.size(); a++)
		{
			const std::vector<Weight>& vw = vertexWeights[a];
			for( std::vector<Weight>::const_iterator it = vw.begin(); it != vw.end(); ++it)
				boneWeights[it->mBone].push_back( aiVertexWeight( a, it->mWeight));
		}

		// and finally copy the vertex weight list over to the mesh's bones
		std::vector<bool> abNoNeed(pMesh->mNumBones,false);
		bChanged = false;

		for( unsigned int a = 0; a < pMesh->mNumBones; a++)
		{
			const std::vector<aiVertexWeight>& bw = boneWeights[a];
			aiBone* bone = pMesh->mBones[a];

			// ignore the bone if no vertex weights were removed there

			// FIX (Aramis, 07|22|08)
			// NO! we can't ignore it in this case ... it is possible that
			// the number of weights did not change, but the weight values did.

			// if( bw.size() == bone->mNumWeights)
			//	continue;

			// FIX (Aramis, 07|21|08)
			// It is possible that all weights of a bone have been removed.
			// This would naturally cause an exception in &bw[0].
			if ( bw.empty() )
			{
				abNoNeed[a] = bChanged = true;
				continue;
			}

			// copy the weight list. should always be less weights than before, so we don't need a new allocation
			ai_assert( bw.size() <= bone->mNumWeights);
			bone->mNumWeights = (unsigned int) bw.size();
			::memcpy( bone->mWeights, &bw[0], bw.size() * sizeof( aiVertexWeight));
		}

		if (bChanged)
		{
			// the number of new bones is smaller than before, so we can
			// reuse the old array, too.
			aiBone** ppcCur = pMesh->mBones;
			aiBone** ppcSrc = ppcCur;

			for (std::vector<bool>::const_iterator
				iter  = abNoNeed.begin();
				iter != abNoNeed.end()  ;++iter)
			{
				if (*iter)
				{
					delete *ppcSrc;
					--pMesh->mNumBones;
				}
				else *ppcCur++ = *ppcSrc;
				++ppcSrc;
			}
		}
	}
}
