/*
Open Asset Import Library (assimp)
----------------------------------------------------------------------

Copyright (c) 2006-2019, assimp team


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  following disclaimer.

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*/

#include <assimp/Subdivision.h>
#include <assimp/SceneCombiner.h>
#include <assimp/SpatialSort.h>
#include "ProcessHelper.h"
#include <assimp/Vertex.h>
#include <assimp/ai_assert.h>
#include <stdio.h>

using namespace Assimp;
void mydummy() {}

// ------------------------------------------------------------------------------------------------
/** Subdivider stub class to implement the Catmull-Clarke subdivision algorithm. The
 *  implementation is basing on recursive refinement. Directly evaluating the result is also
 *  possible and much quicker, but it depends on lengthy matrix lookup tables. */
// ------------------------------------------------------------------------------------------------
class CatmullClarkSubdivider : public Subdivider
{
public:
    void Subdivide (aiMesh* mesh, aiMesh*& out, unsigned int num, bool discard_input);
    void Subdivide (aiMesh** smesh, size_t nmesh,
        aiMesh** out, unsigned int num, bool discard_input);

    // ---------------------------------------------------------------------------
    /** Intermediate description of an edge between two corners of a polygon*/
    // ---------------------------------------------------------------------------
    struct Edge
    {
        Edge()
            : ref(0)
        {}
        Vertex edge_point, midpoint;
        unsigned int ref;
    };

    typedef std::vector<unsigned int> UIntVector;
    typedef std::map<uint64_t,Edge> EdgeMap;

    // ---------------------------------------------------------------------------
    // Hashing function to derive an index into an #EdgeMap from two given
    // 'unsigned int' vertex coordinates (!!distinct coordinates - same
    // vertex position == same index!!).
    // NOTE - this leads to rare hash collisions if a) sizeof(unsigned int)>4
    // and (id[0]>2^32-1 or id[0]>2^32-1).
    // MAKE_EDGE_HASH() uses temporaries, so INIT_EDGE_HASH() needs to be put
    // at the head of every function which is about to use MAKE_EDGE_HASH().
    // Reason is that the hash is that hash construction needs to hold the
    // invariant id0<id1 to identify an edge - else two hashes would refer
    // to the same edge.
    // ---------------------------------------------------------------------------
#define MAKE_EDGE_HASH(id0,id1) (eh_tmp0__=id0,eh_tmp1__=id1,\
    (eh_tmp0__<eh_tmp1__?std::swap(eh_tmp0__,eh_tmp1__):mydummy()),(uint64_t)eh_tmp0__^((uint64_t)eh_tmp1__<<32u))


#define INIT_EDGE_HASH_TEMPORARIES()\
    unsigned int eh_tmp0__, eh_tmp1__;

private:
    void InternSubdivide (const aiMesh* const * smesh,
        size_t nmesh,aiMesh** out, unsigned int num);
};


// ------------------------------------------------------------------------------------------------
// Construct a subdivider of a specific type
Subdivider* Subdivider::Create (Algorithm algo)
{
    switch (algo)
    {
    case CATMULL_CLARKE:
        return new CatmullClarkSubdivider();
    };

    ai_assert(false);
    return NULL; // shouldn't happen
}

// ------------------------------------------------------------------------------------------------
// Call the Catmull Clark subdivision algorithm for one mesh
void  CatmullClarkSubdivider::Subdivide (
    aiMesh* mesh,
    aiMesh*& out,
    unsigned int num,
    bool discard_input
    )
{
    ai_assert(mesh != out);
    
    Subdivide(&mesh,1,&out,num,discard_input);
}

// ------------------------------------------------------------------------------------------------
// Call the Catmull Clark subdivision algorithm for multiple meshes
void CatmullClarkSubdivider::Subdivide (
    aiMesh** smesh,
    size_t nmesh,
    aiMesh** out,
    unsigned int num,
    bool discard_input
    )
{
    ai_assert( NULL != smesh );
    ai_assert( NULL != out );

    // course, both regions may not overlap
    ai_assert(smesh<out || smesh+nmesh>out+nmesh);
    if (!num) {
        // No subdivision at all. Need to copy all the meshes .. argh.
        if (discard_input) {
            for (size_t s = 0; s < nmesh; ++s) {
                out[s] = smesh[s];
                smesh[s] = NULL;
            }
        }
        else {
            for (size_t s = 0; s < nmesh; ++s) {
                SceneCombiner::Copy(out+s,smesh[s]);
            }
        }
        return;
    }

    std::vector<aiMesh*> inmeshes;
    std::vector<aiMesh*> outmeshes;
    std::vector<unsigned int> maptbl;

    inmeshes.reserve(nmesh);
    outmeshes.reserve(nmesh);
    maptbl.reserve(nmesh);

    // Remove pure line and point meshes from the working set to reduce the
    // number of edge cases the subdivider is forced to deal with. Line and
    // point meshes are simply passed through.
    for (size_t s = 0; s < nmesh; ++s) {
        aiMesh* i = smesh[s];
        // FIX - mPrimitiveTypes might not yet be initialized
        if (i->mPrimitiveTypes && (i->mPrimitiveTypes & (aiPrimitiveType_LINE|aiPrimitiveType_POINT))==i->mPrimitiveTypes) {
            ASSIMP_LOG_DEBUG("Catmull-Clark Subdivider: Skipping pure line/point mesh");

            if (discard_input) {
                out[s] = i;
                smesh[s] = NULL;
            }
            else {
                SceneCombiner::Copy(out+s,i);
            }
            continue;
        }

        outmeshes.push_back(NULL);inmeshes.push_back(i);
        maptbl.push_back(static_cast<unsigned int>(s));
    }

    // Do the actual subdivision on the preallocated storage. InternSubdivide
    // *always* assumes that enough storage is available, it does not bother
    // checking any ranges.
    ai_assert(inmeshes.size()==outmeshes.size()&&inmeshes.size()==maptbl.size());
    if (inmeshes.empty()) {
        ASSIMP_LOG_WARN("Catmull-Clark Subdivider: Pure point/line scene, I can't do anything");
        return;
    }
    InternSubdivide(&inmeshes.front(),inmeshes.size(),&outmeshes.front(),num);
    for (unsigned int i = 0; i < maptbl.size(); ++i) {
        ai_assert(nullptr != outmeshes[i]);
        out[maptbl[i]] = outmeshes[i];
    }

    if (discard_input) {
        for (size_t s = 0; s < nmesh; ++s) {
            delete smesh[s];
        }
    }
}

// ------------------------------------------------------------------------------------------------
// Note - this is an implementation of the standard (recursive) Cm-Cl algorithm without further
// optimizations (except we're using some nice LUTs). A description of the algorithm can be found
// here: http://en.wikipedia.org/wiki/Catmull-Clark_subdivision_surface
//
// The code is mostly O(n), however parts are O(nlogn) which is therefore the algorithm's
// expected total runtime complexity. The implementation is able to work in-place on the same
// mesh arrays. Calling #InternSubdivide() directly is not encouraged. The code can operate
// in-place unless 'smesh' and 'out' are equal (no strange overlaps or reorderings).
// Previous data is replaced/deleted then.
// ------------------------------------------------------------------------------------------------
void CatmullClarkSubdivider::InternSubdivide (
    const aiMesh* const * smesh,
    size_t nmesh,
    aiMesh** out,
    unsigned int num
    )
{
    ai_assert(NULL != smesh && NULL != out);
    INIT_EDGE_HASH_TEMPORARIES();

    // no subdivision requested or end of recursive refinement
    if (!num) {
        return;
    }

    UIntVector maptbl;
    SpatialSort spatial;

    // ---------------------------------------------------------------------
    // 0. Offset table to index all meshes continuously, generate a spatially
    // sorted representation of all vertices in all meshes.
    // ---------------------------------------------------------------------
    typedef std::pair<unsigned int,unsigned int> IntPair;
    std::vector<IntPair> moffsets(nmesh);
    unsigned int totfaces = 0, totvert = 0;
    for (size_t t = 0; t < nmesh; ++t) {
        const aiMesh* mesh = smesh[t];

        spatial.Append(mesh->mVertices,mesh->mNumVertices,sizeof(aiVector3D),false);
        moffsets[t] = IntPair(totfaces,totvert);

        totfaces += mesh->mNumFaces;
        totvert  += mesh->mNumVertices;
    }

    spatial.Finalize();
    const unsigned int num_unique = spatial.GenerateMappingTable(maptbl,ComputePositionEpsilon(smesh,nmesh));


#define FLATTEN_VERTEX_IDX(mesh_idx, vert_idx) (moffsets[mesh_idx].second+vert_idx)
#define   FLATTEN_FACE_IDX(mesh_idx, face_idx) (moffsets[mesh_idx].first+face_idx)

    // ---------------------------------------------------------------------
    // 1. Compute the centroid point for all faces
    // ---------------------------------------------------------------------
    std::vector<Vertex> centroids(totfaces);
    unsigned int nfacesout = 0;
    for (size_t t = 0, n = 0; t < nmesh; ++t) {
        const aiMesh* mesh = smesh[t];
        for (unsigned int i = 0; i < mesh->mNumFaces;++i,++n)
        {
            const aiFace& face = mesh->mFaces[i];
            Vertex& c = centroids[n];

            for (unsigned int a = 0; a < face.mNumIndices;++a) {
                c += Vertex(mesh,face.mIndices[a]);
            }

            c /= static_cast<float>(face.mNumIndices);
            nfacesout += face.mNumIndices;
        }
    }

    {
    // we want edges to go away before the recursive calls so begin a new scope
    EdgeMap edges;

    // ---------------------------------------------------------------------
    // 2. Set each edge point to be the average of all neighbouring
    // face points and original points. Every edge exists twice
    // if there is a neighboring face.
    // ---------------------------------------------------------------------
    for (size_t t = 0; t < nmesh; ++t) {
        const aiMesh* mesh = smesh[t];

        for (unsigned int i = 0; i < mesh->mNumFaces;++i)   {
            const aiFace& face = mesh->mFaces[i];

            for (unsigned int p =0; p< face.mNumIndices; ++p) {
                const unsigned int id[] = {
                    face.mIndices[p],
                    face.mIndices[p==face.mNumIndices-1?0:p+1]
                };
                const unsigned int mp[] = {
                    maptbl[FLATTEN_VERTEX_IDX(t,id[0])],
                    maptbl[FLATTEN_VERTEX_IDX(t,id[1])]
                };

                Edge& e = edges[MAKE_EDGE_HASH(mp[0],mp[1])];
                e.ref++;
                if (e.ref<=2) {
                    if (e.ref==1) { // original points (end points) - add only once
                        e.edge_point = e.midpoint = Vertex(mesh,id[0])+Vertex(mesh,id[1]);
                        e.midpoint *= 0.5f;
                    }
                    e.edge_point += centroids[FLATTEN_FACE_IDX(t,i)];
                }
            }
        }
    }

    // ---------------------------------------------------------------------
    // 3. Normalize edge points
    // ---------------------------------------------------------------------
    {unsigned int bad_cnt = 0;
    for (EdgeMap::iterator it = edges.begin(); it != edges.end(); ++it) {
        if ((*it).second.ref < 2) {
            ai_assert((*it).second.ref);
            ++bad_cnt;
        }
        (*it).second.edge_point *= 1.f/((*it).second.ref+2.f);
    }

    if (bad_cnt) {
        // Report the number of bad edges. bad edges are referenced by less than two
        // faces in the mesh. They occur at outer model boundaries in non-closed
        // shapes.
        ASSIMP_LOG_DEBUG_F("Catmull-Clark Subdivider: got ", bad_cnt, " bad edges touching only one face (totally ", 
            static_cast<unsigned int>(edges.size()), " edges). ");
    }}

    // ---------------------------------------------------------------------
    // 4. Compute a vertex-face adjacency table. We can't reuse the code
    // from VertexTriangleAdjacency because we need the table for multiple
    // meshes and out vertex indices need to be mapped to distinct values
    // first.
    // ---------------------------------------------------------------------
    UIntVector faceadjac(nfacesout), cntadjfac(maptbl.size(),0), ofsadjvec(maptbl.size()+1,0); {
    for (size_t t = 0; t < nmesh; ++t) {
        const aiMesh* const minp = smesh[t];
        for (unsigned int i = 0; i < minp->mNumFaces; ++i) {

            const aiFace& f = minp->mFaces[i];
            for (unsigned int n = 0; n < f.mNumIndices; ++n) {
                ++cntadjfac[maptbl[FLATTEN_VERTEX_IDX(t,f.mIndices[n])]];
            }
        }
    }
    unsigned int cur = 0;
    for (size_t i = 0; i < cntadjfac.size(); ++i) {
        ofsadjvec[i+1] = cur;
        cur += cntadjfac[i];
    }
    for (size_t t = 0; t < nmesh; ++t) {
        const aiMesh* const minp = smesh[t];
        for (unsigned int i = 0; i < minp->mNumFaces; ++i) {

            const aiFace& f = minp->mFaces[i];
            for (unsigned int n = 0; n < f.mNumIndices; ++n) {
                faceadjac[ofsadjvec[1+maptbl[FLATTEN_VERTEX_IDX(t,f.mIndices[n])]]++] = FLATTEN_FACE_IDX(t,i);
            }
        }
    }

    // check the other way round for consistency
#ifdef ASSIMP_BUILD_DEBUG

    for (size_t t = 0; t < ofsadjvec.size()-1; ++t) {
        for (unsigned int m = 0; m <  cntadjfac[t]; ++m) {
            const unsigned int fidx = faceadjac[ofsadjvec[t]+m];
            ai_assert(fidx < totfaces);
            for (size_t n = 1; n < nmesh; ++n) {

                if (moffsets[n].first > fidx) {
                    const aiMesh* msh = smesh[--n];
                    const aiFace& f = msh->mFaces[fidx-moffsets[n].first];

                    bool haveit = false;
                    for (unsigned int i = 0; i < f.mNumIndices; ++i) {
                        if (maptbl[FLATTEN_VERTEX_IDX(n,f.mIndices[i])]==(unsigned int)t) {
                            haveit = true;
                            break;
                        }
                    }
                    ai_assert(haveit);
                    if (!haveit) {
                        ASSIMP_LOG_DEBUG("Catmull-Clark Subdivider: Index not used");
                    }
                    break;
                }
            }
        }
    }

#endif
    }

#define GET_ADJACENT_FACES_AND_CNT(vidx,fstartout,numout) \
    fstartout = &faceadjac[ofsadjvec[vidx]], numout = cntadjfac[vidx]

    typedef std::pair<bool,Vertex> TouchedOVertex;
    std::vector<TouchedOVertex > new_points(num_unique,TouchedOVertex(false,Vertex()));
    // ---------------------------------------------------------------------
    // 5. Spawn a quad from each face point to the corresponding edge points
    // the original points being the fourth quad points.
    // ---------------------------------------------------------------------
    for (size_t t = 0; t < nmesh; ++t) {
        const aiMesh* const minp = smesh[t];
        aiMesh* const mout = out[t] = new aiMesh();

        for (unsigned int a  = 0; a < minp->mNumFaces; ++a) {
            mout->mNumFaces += minp->mFaces[a].mNumIndices;
        }

        // We need random access to the old face buffer, so reuse is not possible.
        mout->mFaces = new aiFace[mout->mNumFaces];

        mout->mNumVertices = mout->mNumFaces*4;
        mout->mVertices = new aiVector3D[mout->mNumVertices];

        // quads only, keep material index
        mout->mPrimitiveTypes = aiPrimitiveType_POLYGON;
        mout->mMaterialIndex = minp->mMaterialIndex;

        if (minp->HasNormals()) {
            mout->mNormals = new aiVector3D[mout->mNumVertices];
        }

        if (minp->HasTangentsAndBitangents()) {
            mout->mTangents = new aiVector3D[mout->mNumVertices];
            mout->mBitangents = new aiVector3D[mout->mNumVertices];
        }

        for(unsigned int i = 0; minp->HasTextureCoords(i); ++i) {
            mout->mTextureCoords[i] = new aiVector3D[mout->mNumVertices];
            mout->mNumUVComponents[i] = minp->mNumUVComponents[i];
        }

        for(unsigned int i = 0; minp->HasVertexColors(i); ++i) {
            mout->mColors[i] = new aiColor4D[mout->mNumVertices];
        }

        mout->mNumVertices = mout->mNumFaces<<2u;
        for (unsigned int i = 0, v = 0, n = 0; i < minp->mNumFaces;++i) {

            const aiFace& face = minp->mFaces[i];
            for (unsigned int a = 0; a < face.mNumIndices;++a)  {

                // Get a clean new face.
                aiFace& faceOut = mout->mFaces[n++];
                faceOut.mIndices = new unsigned int [faceOut.mNumIndices = 4];

                // Spawn a new quadrilateral (ccw winding) for this original point between:
                // a) face centroid
                centroids[FLATTEN_FACE_IDX(t,i)].SortBack(mout,faceOut.mIndices[0]=v++);

                // b) adjacent edge on the left, seen from the centroid
                const Edge& e0 = edges[MAKE_EDGE_HASH(maptbl[FLATTEN_VERTEX_IDX(t,face.mIndices[a])],
                    maptbl[FLATTEN_VERTEX_IDX(t,face.mIndices[a==face.mNumIndices-1?0:a+1])
                    ])];  // fixme: replace with mod face.mNumIndices?

                // c) adjacent edge on the right, seen from the centroid
                const Edge& e1 = edges[MAKE_EDGE_HASH(maptbl[FLATTEN_VERTEX_IDX(t,face.mIndices[a])],
                    maptbl[FLATTEN_VERTEX_IDX(t,face.mIndices[!a?face.mNumIndices-1:a-1])
                    ])];  // fixme: replace with mod face.mNumIndices?

                e0.edge_point.SortBack(mout,faceOut.mIndices[3]=v++);
                e1.edge_point.SortBack(mout,faceOut.mIndices[1]=v++);

                // d= original point P with distinct index i
                // F := 0
                // R := 0
                // n := 0
                // for each face f containing i
                //    F := F+ centroid of f
                //    R := R+ midpoint of edge of f from i to i+1
                //    n := n+1
                //
                // (F+2R+(n-3)P)/n
                const unsigned int org = maptbl[FLATTEN_VERTEX_IDX(t,face.mIndices[a])];
                TouchedOVertex& ov = new_points[org];

                if (!ov.first) {
                    ov.first = true;

                    const unsigned int* adj; unsigned int cnt;
                    GET_ADJACENT_FACES_AND_CNT(org,adj,cnt);

                    if (cnt < 3) {
                        ov.second = Vertex(minp,face.mIndices[a]);
                    }
                    else {

                        Vertex F,R;
                        for (unsigned int o = 0; o < cnt; ++o) {
                            ai_assert(adj[o] < totfaces);
                            F += centroids[adj[o]];

                            // adj[0] is a global face index - search the face in the mesh list
                            const aiMesh* mp = NULL;
                            size_t nidx;

                            if (adj[o] < moffsets[0].first) {
                                mp = smesh[nidx=0];
                            }
                            else {
                                for (nidx = 1; nidx<= nmesh; ++nidx) {
                                    if (nidx == nmesh ||moffsets[nidx].first > adj[o]) {
                                        mp = smesh[--nidx];
                                        break;
                                    }
                                }
                            }

                            ai_assert(adj[o]-moffsets[nidx].first < mp->mNumFaces);
                            const aiFace& f = mp->mFaces[adj[o]-moffsets[nidx].first];
                            bool haveit = false;

                            // find our original point in the face
                            for (unsigned int m = 0; m < f.mNumIndices; ++m) {
                                if (maptbl[FLATTEN_VERTEX_IDX(nidx,f.mIndices[m])] == org) {

                                    // add *both* edges. this way, we can be sure that we add
                                    // *all* adjacent edges to R. In a closed shape, every
                                    // edge is added twice - so we simply leave out the
                                    // factor 2.f in the amove formula and get the right
                                    // result.

                                    const Edge& c0 = edges[MAKE_EDGE_HASH(org,maptbl[FLATTEN_VERTEX_IDX(
                                        nidx,f.mIndices[!m?f.mNumIndices-1:m-1])])];
                                    // fixme: replace with mod face.mNumIndices?

                                    const Edge& c1 = edges[MAKE_EDGE_HASH(org,maptbl[FLATTEN_VERTEX_IDX(
                                        nidx,f.mIndices[m==f.mNumIndices-1?0:m+1])])];
                                    // fixme: replace with mod face.mNumIndices?
                                    R += c0.midpoint+c1.midpoint;

                                    haveit = true;
                                    break;
                                }
                            }

                            // this invariant *must* hold if the vertex-to-face adjacency table is valid
                            ai_assert(haveit);
                            if ( !haveit ) {
                                ASSIMP_LOG_WARN( "OBJ: no name for material library specified." );
                            }
                        }

                        const float div = static_cast<float>(cnt), divsq = 1.f/(div*div);
                        ov.second = Vertex(minp,face.mIndices[a])*((div-3.f) / div) + R*divsq + F*divsq;
                    }
                }
                ov.second.SortBack(mout,faceOut.mIndices[2]=v++);
            }
        }
    }
    }  // end of scope for edges, freeing its memory

    // ---------------------------------------------------------------------
    // 7. Apply the next subdivision step.
    // ---------------------------------------------------------------------
    if (num != 1) {
        std::vector<aiMesh*> tmp(nmesh);
        InternSubdivide (out,nmesh,&tmp.front(),num-1);
        for (size_t i = 0; i < nmesh; ++i) {
            delete out[i];
            out[i] = tmp[i];
        }
    }
}
