/*

Open Asset Import Library (assimp)

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  following disclaimer.

* Redistributions in binary form must reproduce the above

  copyright notice, this list of conditions and the

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*/

#include <assimp/Subdivision.h>

#include <assimp/SceneCombiner.h>

#include <assimp/SpatialSort.h>

#include <assimp/Vertex.h>

#include <assimp/ai_assert.h>

#include "PostProcessing/ProcessHelper.h"

#include <stdio.h>

#include <unordered_map>

using namespace Assimp;

void mydummy() {}

#ifdef _MSC_VER

#pragma warning(disable : 4709)

#endif // _MSC_VER

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

/** 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::unordered_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 nullptr; // 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(nullptr != smesh);

    ai_assert(nullptr != 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] = nullptr;

            }

        } 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_VERBOSE_DEBUG("Catmull-Clark Subdivider: Skipping pure line/point mesh");

            if (discard_input) {

                out[s] = i;

                smesh[s] = nullptr;

            } else {

                SceneCombiner::Copy(out + s, i);

            }

            continue;

        }

        outmeshes.push_back(nullptr);

        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());

    ai_assert(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(nullptr != smesh);

    ai_assert(nullptr != 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_VERBOSE_DEBUG("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_VERBOSE_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 = nullptr;

                                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;

                                        }

                                    }

                                }

                                if (mp == nullptr) {

                                    continue;

                                }

                                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];

        }

    }

}