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/** @file  OptimizeMeshes.cpp
 *  @brief Implementation of the aiProcess_OptimizeMeshes step
 */


#ifndef ASSIMP_BUILD_NO_OPTIMIZEMESHES_PROCESS


#include "OptimizeMeshes.h"
#include "ProcessHelper.h"
#include "SceneCombiner.h"
#include "Exceptional.h"

using namespace Assimp;

static const unsigned int NotSet   = 0xffffffff;
static const unsigned int DeadBeef = 0xdeadbeef;

// ------------------------------------------------------------------------------------------------
// Constructor to be privately used by Importer
OptimizeMeshesProcess::OptimizeMeshesProcess()
    : mScene()
    , pts(false)
    , max_verts( NotSet )
    , max_faces( NotSet ) {
    // empty
}

// ------------------------------------------------------------------------------------------------
// Destructor, private as well
OptimizeMeshesProcess::~OptimizeMeshesProcess() {
    // empty
}

// ------------------------------------------------------------------------------------------------
// Returns whether the processing step is present in the given flag field.
bool OptimizeMeshesProcess::IsActive( unsigned int pFlags) const
{
	// Our behaviour needs to be different if the SortByPType or SplitLargeMeshes
	// steps are active. Thus we need to query their flags here and store the
	// information, although we're breaking const-correctness. 
	// That's a serious design flaw, consider redesign.
	if( 0 != (pFlags & aiProcess_OptimizeMeshes) ) {
		pts = (0 != (pFlags & aiProcess_SortByPType));
        max_verts = ( 0 != ( pFlags & aiProcess_SplitLargeMeshes ) ) ? DeadBeef : max_verts;
		return true;
	}
	return false;
}

// ------------------------------------------------------------------------------------------------
// Setup properties for the post-processing step
void OptimizeMeshesProcess::SetupProperties(const Importer* pImp)
{
    if( max_verts == DeadBeef /* magic hack */ ) {
		max_faces = pImp->GetPropertyInteger(AI_CONFIG_PP_SLM_TRIANGLE_LIMIT,AI_SLM_DEFAULT_MAX_TRIANGLES);
		max_verts = pImp->GetPropertyInteger(AI_CONFIG_PP_SLM_VERTEX_LIMIT,AI_SLM_DEFAULT_MAX_VERTICES);
	}
}

// ------------------------------------------------------------------------------------------------
// Execute step
void OptimizeMeshesProcess::Execute( aiScene* pScene)
{
	const unsigned int num_old = pScene->mNumMeshes;
	if (num_old <= 1) {
		DefaultLogger::get()->debug("Skipping OptimizeMeshesProcess");
		return;
	}

	DefaultLogger::get()->debug("OptimizeMeshesProcess begin");
	mScene = pScene;

	// need to clear persistent members from previous runs
	merge_list.resize( 0 );
	output.resize( 0 );

    // ensure we have the right sizes
	merge_list.reserve(pScene->mNumMeshes);
	output.reserve(pScene->mNumMeshes);

	// Prepare lookup tables
	meshes.resize(pScene->mNumMeshes);
	FindInstancedMeshes(pScene->mRootNode);
    if( max_verts == DeadBeef ) /* undo the magic hack */
		max_verts = NotSet;

	// ... instanced meshes are immediately processed and added to the output list
	for (unsigned int i = 0, n = 0; i < pScene->mNumMeshes;++i) {
		meshes[i].vertex_format = GetMeshVFormatUnique(pScene->mMeshes[i]);

		if (meshes[i].instance_cnt > 1 && meshes[i].output_id == NotSet ) {
			meshes[i].output_id = n++;
			output.push_back(mScene->mMeshes[i]);
		}
	}

	// and process all nodes in the scenegraph recursively
	ProcessNode(pScene->mRootNode);
	if (!output.size()) {
		throw DeadlyImportError("OptimizeMeshes: No meshes remaining; there's definitely something wrong");
	}

	meshes.resize( 0 );
	ai_assert(output.size() <= num_old);

	mScene->mNumMeshes = output.size();
	std::copy(output.begin(),output.end(),mScene->mMeshes);

	if (output.size() != num_old) {
		char tmp[512];
		::sprintf(tmp,"OptimizeMeshesProcess finished. Input meshes: %u, Output meshes: %u",num_old,pScene->mNumMeshes);
		DefaultLogger::get()->info(tmp);
    } else {
        DefaultLogger::get()->debug( "OptimizeMeshesProcess finished" );
    }
}

// ------------------------------------------------------------------------------------------------
// Process meshes for a single node
void OptimizeMeshesProcess::ProcessNode( aiNode* pNode)
{
	for (unsigned int i = 0; i < pNode->mNumMeshes;++i) {
		unsigned int& im = pNode->mMeshes[i];

		if (meshes[im].instance_cnt > 1) {
			im = meshes[im].output_id;
		}
		else  {
			merge_list.resize( 0 );
			unsigned int verts = 0, faces = 0;

			// Find meshes to merge with us
			for (unsigned int a = i+1; a < pNode->mNumMeshes;++a) {
				unsigned int am = pNode->mMeshes[a];
				if (meshes[am].instance_cnt == 1 && CanJoin(im,am,verts,faces)) {

					merge_list.push_back(mScene->mMeshes[am]);
					verts += mScene->mMeshes[am]->mNumVertices;
					faces += mScene->mMeshes[am]->mNumFaces;

					--pNode->mNumMeshes;
                    for( unsigned int n = a; n < pNode->mNumMeshes; ++n ) {
                        pNode->mMeshes[ n ] = pNode->mMeshes[ n + 1 ];
                    }

					--a;
				}
			}

			// and merge all meshes which we found, replace the old ones
			if (!merge_list.empty()) {
				merge_list.push_back(mScene->mMeshes[im]);

				aiMesh* out;
				SceneCombiner::MergeMeshes(&out,0,merge_list.begin(),merge_list.end());
				output.push_back(out);
			} else {
				output.push_back(mScene->mMeshes[im]);
			}
			im = output.size()-1;
		}
	}


    for( unsigned int i = 0; i < pNode->mNumChildren; ++i ) {
        ProcessNode( pNode->mChildren[ i ] );
    }
}

// ------------------------------------------------------------------------------------------------
// Check whether two meshes can be joined
bool OptimizeMeshesProcess::CanJoin ( unsigned int a, unsigned int b, unsigned int verts, unsigned int faces )
{
	if (meshes[a].vertex_format != meshes[b].vertex_format)
		return false;

	aiMesh* ma = mScene->mMeshes[a], *mb = mScene->mMeshes[b];

	if ((NotSet != max_verts && verts+mb->mNumVertices > max_verts) ||
		(NotSet != max_faces && faces+mb->mNumFaces    > max_faces)) {
		return false;
	}

	// Never merge unskinned meshes with skinned meshes
	if (ma->mMaterialIndex != mb->mMaterialIndex || ma->HasBones() != mb->HasBones())
		return false;

	// Never merge meshes with different kinds of primitives if SortByPType did already
	// do its work. We would destroy everything again ...
	if (pts && ma->mPrimitiveTypes != mb->mPrimitiveTypes)
		return false;

	// If both meshes are skinned, check whether we have many bones defined in both meshes. 
	// If yes, we can join them. 
	if (ma->HasBones()) {
		// TODO
		return false;
	}
	return true;
}

// ------------------------------------------------------------------------------------------------
// Build a LUT of all instanced meshes
void OptimizeMeshesProcess::FindInstancedMeshes (aiNode* pNode)
{
    for( unsigned int i = 0; i < pNode->mNumMeshes; ++i ) {
        ++meshes[ pNode->mMeshes[ i ] ].instance_cnt;
    }

    for( unsigned int i = 0; i < pNode->mNumChildren; ++i ) {
        FindInstancedMeshes( pNode->mChildren[ i ] );
    }
}

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

#endif // !! ASSIMP_BUILD_NO_OPTIMIZEMESHES_PROCESS