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

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  following disclaimer.

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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];
        }
    }
}
