/*
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Open Asset Import Library (assimp)
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*/

/** @file Implementation of the post processing step to generate face
* normals for all imported faces.
*/

#include "ph.hpp"

// internal headers
#include "GenVertexNormalsProcess.h"
#include "ProcessHelper.h"
#include "Exceptional.h"
#include "qnan.h"

using namespace Assimp;

// ------------------------------------------------------------------------------------------------
// Constructor to be privately used by Importer
GenVertexNormalsProcess::GenVertexNormalsProcess()
: configMaxAngle( AI_DEG_TO_RAD( 175.f ) ) {
    // empty
}

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

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

// ------------------------------------------------------------------------------------------------
// Executes the post processing step on the given imported data.
void GenVertexNormalsProcess::SetupProperties(const Importer* pImp)
{
    // Get the current value of the AI_CONFIG_PP_GSN_MAX_SMOOTHING_ANGLE property
    configMaxAngle = pImp->GetPropertyFloat(AI_CONFIG_PP_GSN_MAX_SMOOTHING_ANGLE,175.f);
    configMaxAngle = AI_DEG_TO_RAD(std::max(std::min(configMaxAngle,175.0f),0.0f));
}

// ------------------------------------------------------------------------------------------------
// Executes the post processing step on the given imported data.
void GenVertexNormalsProcess::Execute( aiScene* pScene)
{
    DefaultLogger::get()->debug("GenVertexNormalsProcess begin");

    if (pScene->mFlags & AI_SCENE_FLAGS_NON_VERBOSE_FORMAT)
        throw DeadlyImportError("Post-processing order mismatch: expecting pseudo-indexed (\"verbose\") vertices here");

    bool bHas = false;
    for( unsigned int a = 0; a < pScene->mNumMeshes; a++)
    {
        if(GenMeshVertexNormals( pScene->mMeshes[a],a))
            bHas = true;
    }

    if (bHas)   {
        DefaultLogger::get()->info("GenVertexNormalsProcess finished. "
            "Vertex normals have been calculated");
    }
    else DefaultLogger::get()->debug("GenVertexNormalsProcess finished. "
        "Normals are already there");
}

// ------------------------------------------------------------------------------------------------
// Executes the post processing step on the given imported data.
bool GenVertexNormalsProcess::GenMeshVertexNormals (aiMesh* pMesh, unsigned int meshIndex)
{
    if (NULL != pMesh->mNormals)
        return false;

    // If the mesh consists of lines and/or points but not of
    // triangles or higher-order polygons the normal vectors
    // are undefined.
    if (!(pMesh->mPrimitiveTypes & (aiPrimitiveType_TRIANGLE | aiPrimitiveType_POLYGON)))
    {
        DefaultLogger::get()->info("Normal vectors are undefined for line and point meshes");
        return false;
    }

    // Allocate the array to hold the output normals
    const float qnan = std::numeric_limits<float>::quiet_NaN();
    pMesh->mNormals = new aiVector3D[pMesh->mNumVertices];

    // Compute per-face normals but store them per-vertex
    for( unsigned int a = 0; a < pMesh->mNumFaces; a++)
    {
        const aiFace& face = pMesh->mFaces[a];
        if (face.mNumIndices < 3)
        {
            // either a point or a line -> no normal vector
            for (unsigned int i = 0;i < face.mNumIndices;++i) {
                pMesh->mNormals[face.mIndices[i]] = aiVector3D(qnan);
            }

            continue;
        }

        const aiVector3D* pV1 = &pMesh->mVertices[face.mIndices[0]];
        const aiVector3D* pV2 = &pMesh->mVertices[face.mIndices[1]];
        const aiVector3D* pV3 = &pMesh->mVertices[face.mIndices[face.mNumIndices-1]];
        const aiVector3D vNor = ((*pV2 - *pV1) ^ (*pV3 - *pV1));

        for (unsigned int i = 0;i < face.mNumIndices;++i) {
            pMesh->mNormals[face.mIndices[i]] = vNor;
        }
    }

    // Set up a SpatialSort to quickly find all vertices close to a given position
    // check whether we can reuse the SpatialSort of a previous step.
    SpatialSort* vertexFinder = NULL;
    SpatialSort  _vertexFinder;
    float posEpsilon = 1e-5f;
    if (shared) {
        std::vector<std::pair<SpatialSort,float> >* avf;
        shared->GetProperty(AI_SPP_SPATIAL_SORT,avf);
        if (avf)
        {
            std::pair<SpatialSort,float>& blubb = avf->operator [] (meshIndex);
            vertexFinder = &blubb.first;
            posEpsilon = blubb.second;
        }
    }
    if (!vertexFinder)  {
        _vertexFinder.Fill(pMesh->mVertices, pMesh->mNumVertices, sizeof( aiVector3D));
        vertexFinder = &_vertexFinder;
        posEpsilon = ComputePositionEpsilon(pMesh);
    }
    std::vector<unsigned int> verticesFound;
    aiVector3D* pcNew = new aiVector3D[pMesh->mNumVertices];

    if (configMaxAngle >= AI_DEG_TO_RAD( 175.f ))   {
        // There is no angle limit. Thus all vertices with positions close
        // to each other will receive the same vertex normal. This allows us
        // to optimize the whole algorithm a little bit ...
        std::vector<bool> abHad(pMesh->mNumVertices,false);
        for (unsigned int i = 0; i < pMesh->mNumVertices;++i)   {
            if (abHad[i]) {
                continue;
            }

            // Get all vertices that share this one ...
            vertexFinder->FindPositions( pMesh->mVertices[i], posEpsilon, verticesFound);

            aiVector3D pcNor;
            for (unsigned int a = 0; a < verticesFound.size(); ++a) {
                const aiVector3D& v = pMesh->mNormals[verticesFound[a]];
                if (is_not_qnan(v.x))pcNor += v;
            }
            pcNor.NormalizeSafe();

            // Write the smoothed normal back to all affected normals
            for (unsigned int a = 0; a < verticesFound.size(); ++a)
            {
                unsigned int vidx = verticesFound[a];
                pcNew[vidx] = pcNor;
                abHad[vidx] = true;
            }
        }
    }
    // Slower code path if a smooth angle is set. There are many ways to achieve
    // the effect, this one is the most straightforward one.
    else    {
        const float fLimit = std::cos(configMaxAngle);
        for (unsigned int i = 0; i < pMesh->mNumVertices;++i)   {
            // Get all vertices that share this one ...
            vertexFinder->FindPositions( pMesh->mVertices[i] , posEpsilon, verticesFound);

            aiVector3D vr = pMesh->mNormals[i];
            float vrlen = vr.Length();

            aiVector3D pcNor;
            for (unsigned int a = 0; a < verticesFound.size(); ++a) {
                aiVector3D v = pMesh->mNormals[verticesFound[a]];

                // check whether the angle between the two normals is not too large
                // HACK: if v.x is qnan the dot product will become qnan, too
                //   therefore the comparison against fLimit should be false
                //   in every case.
                if (v * vr >= fLimit * vrlen * v.Length())
                    pcNor += v;
            }
            pcNew[i] = pcNor.NormalizeSafe();
        }
    }

    delete[] pMesh->mNormals;
    pMesh->mNormals = pcNew;

    return true;
}
