/****************************************************************************
* VCGLib                                                            o o     *
* Visual and Computer Graphics Library                            o     o   *
*                                                                _   O  _   *
* Copyright(C) 2004-2016                                           \/)\/    *
* Visual Computing Lab                                            /\/|      *
* ISTI - Italian National Research Council                           |      *
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* This program is distributed in the hope that it will be useful,           *
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the             *
* GNU General Public License (http://www.gnu.org/licenses/gpl.txt)          *
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****************************************************************************/

/** \file face/pos.h
 * Definition of vcg:face::Pos class.
 * This file contain the definition of vcg::face::Pos class and the derived vcg::face::PosN class.
 */

#ifndef __VCG_FACE_POS
#define __VCG_FACE_POS

namespace vcg {
namespace face {

/** \addtogroup face */
/*@{*/

// Needed Prototypes (pos is include before topology)
template <class FaceType>
bool IsBorder(FaceType const & f,  const int j );
template <class FaceType>
bool IsManifold(FaceType const & f,  const int j );

/**  Templated over the class face, it stores a \em position over a face in a mesh.
    It contain a pointer to the current face,
    the index of one edge and a pointer to one of the vertices of the edge.
    See also the JumpingPos in jumping_pos.h for an iterator that loops
    around the faces of a vertex without requiring the VF topology.
 */


template <class FaceType>
class Pos
{
public:

    /// The vertex type
    typedef typename FaceType::VertexType VertexType;
    ///The Pos type
    typedef Pos<FaceType> PosType;
    /// The scalar type
    typedef typename VertexType::ScalarType ScalarType;

    /// Pointer to the face of the half-edge
    typename FaceType::FaceType *f;
    /// Index of the edge
    int z;
    /// Pointer to the vertex
    VertexType *v;

    /// Default constructor
    Pos() : f(0), z(-1), v(0) {}
    /// Constructor which associates the half-edge element with a face, its edge and its vertex
    /// \note that the input must be consistent, e.g. it should hold that \c vp==fp->V0(zp) or \c vp==fp->V1(zp)
    Pos(FaceType * const fp, int const zp, VertexType * const vp)
    {
        f=fp; z=zp; v=vp;
        assert((vp==fp->V0(zp))||(vp==fp->V1(zp)));
    }
    Pos(FaceType * const fp, int const zp){f=fp; z=zp; v=f->V(zp);}
    Pos(FaceType * const fp, VertexType * const vp)
    {
        f = fp;
        v = vp;
        for(int i = 0; i < f->VN(); ++i)
            if (f->V(i) == v) { z = f->Prev(i); break;}
    }

    // Official Access functions functions
    VertexType *& V(){ return v; }
    int         & E(){ return z; }
    FaceType   *& F(){ return f; }

    VertexType * V() const { return v; }
    int          E() const { return z; }
    FaceType   * F() const { return f; }

    // Returns the face index of the vertex inside the face.
    // Note that this is DIFFERENT from using the z member that denotes the edge index inside the face.
    // It should holds that Vind != (z+1)%3   &&   Vind == z || Vind = z+2%3
    int VInd() const
    {
        for(int i = 0; i < f->VN(); ++i) if(v==f->V(i)) return i;
        assert(0);
        return -1;
    }


    /// Operator to compare two half-edge
    inline bool operator == ( PosType const & p ) const {
        return (f==p.f && z==p.z && v==p.v);
    }

    /// Operator to compare two half-edge
    inline bool operator != ( PosType const & p ) const {
        return (f!=p.f || z!=p.z || v!=p.v);
    }
    /// Operator to order half-edge; it's compare at the first the face pointers, then the index of the edge and finally the vertex pointers
    inline bool operator <= ( PosType const & p) const {
        return	(f!=p.f)?(f<p.f):
                         (z!=p.z)?(z<p.z):
                                  (v<=p.v);
    }

    /// Operator to order half-edge; it's compare at the first the face pointers, then the index of the edge and finally the vertex pointers
    inline bool operator < ( PosType const & p) const {
        if ((*this)==p)return false;
        return ((*this)<=p);
    }

    /// Assignment operator
    inline PosType & operator = ( const PosType & h ){
        f=h.f;
        z=h.z;
        v=h.v;
        return *this;
    }

    /// Set to null the half-edge
    void SetNull(){
        f=0;
        v=0;
        z=-1;
    }
    /// Check if the half-edge is null
    bool IsNull() const {
        return f==0 || v==0 || z<0;
    }

    //Cambia Faccia lungo z
    // e' uguale a FlipF solo che funziona anche per non manifold.
    /// Change face via z
    void NextF()
    {
        FaceType * t = f;
        f = t->FFp(z);
        z = t->FFi(z);
    }

    // Paolo Cignoni 19/6/99
    // Si muove sulla faccia adiacente a f, lungo uno spigolo che
    // NON e' j, e che e' adiacente a v
    // in questo modo si scandiscono tutte le facce incidenti in un
    // vertice f facendo Next() finche' non si ritorna all'inizio
    // Nota che sul bordo rimbalza, cioe' se lo spigolo !=j e' di bordo
    // restituisce sempre la faccia f ma con nj che e' il nuovo spigolo di bordo
    // vecchi parametri:     	FaceType * & f, VertexType * v, int & j

    /// It moves on the adjacent face incident to v, via a different edge that j
    void NextE()
    {
        assert( f->V(z)==v || f->V(f->Next(z))==v ); // L'edge j deve contenere v
        FlipE();
        FlipF();
        assert( f->V(z)==v || f->V(f->Next(z))==v );
    }
    // Cambia edge mantenendo la stessa faccia e lo stesso vertice
    /// Changes edge maintaining the same face and the same vertex
    void FlipE()
    {
        assert(f->V(f->Prev(z))!=v && (f->V(f->Next(z))==v || f->V((z+0)%f->VN())==v));
        if(f->V(f->Next(z))==v) z=f->Next(z);
        else z= f->Prev(z);
        assert(f->V(f->Prev(z))!=v && (f->V(f->Next(z))==v || f->V((z))==v));
    }

    // Cambia Faccia mantenendo lo stesso vertice e lo stesso edge
    // Vale che he.flipf.flipf= he
    // Se l'he e' di bordo he.flipf()==he
    // Si puo' usare SOLO se l'edge e' 2manifold altrimenti
    // si deve usare nextf

    /// Changes face maintaining the same vertex and the same edge
    void FlipF()
    {
        assert( f->FFp(z)->FFp(f->FFi(z))==f );  // two manifoldness check
        // Check that pos vertex is one of the current z-th edge and it is different from the vert opposite to the edge.
        assert(f->V(f->Prev(z))!=v && (f->V(f->Next(z))==v || f->V((z))==v));
        FaceType *nf=f->FFp(z);
        int nz=f->FFi(z);
        assert(nf->V(nf->Prev(nz))!=v && (nf->V(nf->Next(nz))==v || nf->V((nz))==v));
        f=nf;
        z=nz;
        assert(f->V(f->Prev(z))!=v && (f->V(f->Next(z))==v || f->V(z)==v));
    }

    /// Changes vertex maintaining the same face and the same edge
    void FlipV()
    {
        assert(f->V(f->Prev(z))!=v && (f->V(f->Next(z))==v || f->V(z)==v));

        if(f->V(f->Next(z))==v)
            v=f->V(z);
        else
            v=f->V(f->Next(z));

        assert(f->V(f->Prev(z))!=v && (f->V(f->Next(z))==v || f->V(z)==v));
    }

    /// return the vertex that it should have if we make FlipV;
    VertexType *VFlip() const
    {
        assert(f->cV(f->Prev(z))!=v && (f->cV(f->Next(z))==v || f->cV(z)==v));
        if(f->cV(f->Next(z))==v)	return f->cV(z);
        else			return f->cV(f->Next(z));
    }

    /// return the face that it should have if we make FlipF;
    FaceType *FFlip() const
    {
        //        assert( f->FFp(z)->FFp(f->FFi(z))==f );
        //        assert(f->V(f->Prev(z))!=v);
        //        assert(f->V(f->Next(z))==v || f->V((z+0)%f->VN())==v);
        FaceType *nf=f->FFp(z);
        return nf;
    }


    // Trova il prossimo half-edge di bordo (nhe)
    // tale che
    // --nhe.f adiacente per vertice a he.f
    // --nhe.v adiacente per edge di bordo a he.v
    // l'idea e' che se he e' un half edge di bordo
    // si puo scorrere tutto un bordo facendo
    //
    //		hei=he;
    //		do
    //			hei.Nextb()
    //		while(hei!=he);

    /// Finds the next half-edge border
    void NextB( )
    {
        assert(f->V(f->Prev(z))!=v && (f->V(f->Next(z))==v || f->V(z)==v));
        assert(f->FFp(z)==f); // f is border along j
        // Si deve cambiare faccia intorno allo stesso vertice v
        //finche' non si trova una faccia di bordo.
        do
            NextE();
        while(!IsBorder());

        // L'edge j e' di bordo e deve contenere v
        assert(IsBorder() &&( f->V(z)==v || f->V(f->Next(z))==v ));

        FlipV();
        assert(f->V(f->Prev(z))!=v && (f->V(f->Next(z))==v || f->V(z)==v));
        assert(f->FFp(z)==f); // f is border along j
    }

    /// Finds the next half-edge border
    void NextNotFaux( )
    {
        assert(f->V(f->Prev(z))!=v && (f->V(f->Next(z))==v || f->V(z)==v));
        //assert(f->FFp(z)==f); // f is border along j
        // Si deve cambiare faccia intorno allo stesso vertice v
        //finche' non si trova una faccia di bordo.
        do
        {
            FlipE();
            if (IsFaux()) FlipF();
        }
        while(IsFaux());

        // L'edge j e' di bordo e deve contenere v
        assert((!IsFaux()) &&( f->V(z)==v || f->V(f->Next(z))==v ));

        FlipV();
        assert(f->V(f->Prev(z))!=v && (f->V(f->Next(z))==v || f->V(z)==v));
        //assert(f->FFp(z)==f); // f is border along j
    }

    /// Checks if the half-edge is of border
    bool IsBorder()const
    {
        return face::IsBorder(*f,z);
    }

    bool IsFaux() const
    {
        return (f->IsF(z));
    }

    bool IsManifold()
    {
        return face::IsManifold(*f,z);
    }
    
    void NextEdgeS( )
    {
        assert(f->V(f->Prev(z))!=v && (f->V(f->Next(z))==v || f->V(z)==v));
        assert(IsEdgeS());
        do
        {
            FlipE();
            if (!IsEdgeS()) FlipF();
        }
        while(!IsEdgeS());

        assert(IsEdgeS() &&( f->V(z)==v || f->V(f->Next(z))==v ));

        FlipV();
        assert(f->V(f->Prev(z))!=v && (f->V(f->Next(z))==v || f->V(z)==v));
    }

    bool IsFaceS() const { return f->IsS();}
    bool IsEdgeS() const { return f->IsFaceEdgeS(z);}
    bool IsVertS() const { return v->IsS();}
    
    /*!
     * Returns the angle (in radiant) between the two edges incident on V.
     */
    ScalarType AngleRad() const
    {
        return Angle(f->V(f->Prev(z))->cP()-v->cP(), f->V(f->Next(z))->cP()-v->cP());
    }
    
    /*!
     * Returns the number of vertices incident on the vertex pos is currently pointing to.
     */
    int NumberOfIncidentVertices()
    {
        int  count		 = 0;
        bool on_border = false;
        CheckIncidentFaces(count, on_border);
        if(on_border) return (count/2)+1;
        else					return count;
    }

    /*!
    * Returns the number of faces incident on the vertex pos is currently pointing to.
    */
    int NumberOfIncidentFaces()
    {
        int  count		 = 0;
        bool on_border = false;
        CheckIncidentFaces(count, on_border);
        if(on_border) return count/2;
        else					return count;
    }



    /*!
  * Returns the number of faces incident on the edge the pos is currently pointing to.
  * useful to compute the complexity of a non manifold edge
  */
    int NumberOfFacesOnEdge() const
    {
        int  count		 = 0;
        PosType ht = *this;
        do
        {
            ht.NextF();
            ++count;
        }
        while (ht!=*this);
        return count;
    }
    /** Function to inizialize an half-edge.
        @param fp Puntatore alla faccia
        @param zp Indice dell'edge
        @param vp Puntatore al vertice
    */
    void Set(FaceType  * const fp, int const zp,  VertexType  * const vp)
    {
        f=fp;z=zp;v=vp;
        assert(f->V(f->Prev(z))!=v && (f->V(f->Next(z))==v || f->V(z)==v));
    }

    void Set(FaceType  * const pFace, VertexType  * const pVertex)
    {
        f = pFace;
        v = pVertex;
        for(int i  = 0; i < f->VN(); ++i) if(f->V(i) == v ) {z = f->Prev(i);break;}
    }

    void Assert()
#ifdef _DEBUG
    {
        FaceType ht=*this;
        ht.FlipF();
        ht.FlipF();
        assert(ht==*this);

        ht.FlipE();
        ht.FlipE();
        assert(ht==*this);

        ht.FlipV();
        ht.FlipV();
        assert(ht==*this);
    }
#else
    {}
#endif


protected:
    void CheckIncidentFaces(int & count, bool & on_border)
    {
        PosType ht = *this;
        do
        {
            ++count;
            ht.NextE();
            if(ht.IsBorder()) on_border=true;
        } while (ht != *this);
    }
};

/** Class VFIterator.
    This class is used as an iterator over the VF adjacency.
  It allow to easily traverse all the faces around a given vertex v;
  The faces are traversed in no particular order. No Manifoldness requirement.

  typical example:

    VertexPointer v;
    vcg::face::VFIterator<FaceType> vfi(v);
    for (;!vfi.End();++vfi)
            vfi.F()->ClearV();

        // Alternative

    vcg::face::VFIterator<FaceType> vfi(f, 1);
        while (!vfi.End()){
            vfi.F()->ClearV();
            ++vfi;
        }


    See also the JumpingPos in jumping_pos.h for an iterator that loops
    around the faces of a vertex using FF topology and without requiring the VF topology.

 */

template <typename FaceType>
class VFIterator
{
public:

    /// The vertex type
    typedef typename FaceType::VertexType VertexType;
    /// The Base face type
    typedef  FaceType  VFIFaceType;
    /// The vector type
    typedef typename VertexType::CoordType CoordType;
    /// The scalar type
    typedef typename VertexType::ScalarType ScalarType;

    /// Pointer to the face of the half-edge
    FaceType *f;
    /// Index of the vertex
    int z;

    /// Default constructor
    VFIterator() : f(0), z(-1) {}
    /// Constructor which associates the half-edge elementet with a face and its vertex
    VFIterator(FaceType * _f,  const int &  _z){f = _f; z = _z;  assert(z>=0 && "VFAdj must be initialized");}

    /// Constructor which takes a pointer to vertex
    VFIterator(VertexType * _v){f = _v->VFp(); z = _v->VFi(); assert(z>=0 && "VFAdj must be initialized");}

    VFIFaceType *&	F() { return f;}
    int	&					  I() { return z;}

    // Access to the vertex. Having a VFIterator vfi, it corresponds to
    // vfi.V() = vfi.F()->V(vfi.I())
    inline VertexType *V() const { return f->V(z);}

    inline VertexType * const & V0() const { return f->V0(z);}
    inline VertexType * const & V1() const { return f->V1(z);}
    inline VertexType * const & V2() const { return f->V2(z);}

    bool End() const {return f==0;}
    void operator++() {
        FaceType* t = f;
        f = t->VFp(z);
        z = t->VFi(z);
    }

};

/*@}*/
}	 // end namespace
}	 // end namespace
#endif