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/* ----------------------------------------------------------------------- *

 * This file is part of GEL, http://www.imm.dtu.dk/GEL

 * Copyright (C) the authors and DTU Informatics

 * For license and list of authors, see ../../doc/intro.pdf

 * ----------------------------------------------------------------------- */

/**

@file Walker.h

 Contains class for walking a mesh.

 */

#ifndef __HMESH_HALFEDGEWALKER_H__

#define __HMESH_HALFEDGEWALKER_H__

#include "ConnectivityKernel.h"

namespace HMesh

{

    /** Class for traversing the entities of a HMesh. This class can work as 

     both a vertex and a face circulator but also move in other ways. It is,

     in fact, the only way to traverse the mesh from the users point of view. */

    class Walker

    {

    public:

        /// construct from kernel and a halfedge

        Walker(const ConnectivityKernel& _ck, HalfEdgeID _current);

        /// returned walker has made one step to the next halfedge 

        Walker next() const;

        /// returned walker has made one step to the previous halfedge 

        Walker prev() const;

        /// returned walker has made one step to the opposite halfedge 

        Walker opp() const;

        /// returned walker has circulated vertex clockwise one step

        Walker circulate_vertex_cw() const;

        /// returned walker has circulated vertex counterclockwise one step

        Walker circulate_vertex_ccw() const;

        /// returned walker has circulated face clockwise one step

        Walker circulate_face_cw() const;

        /// returned walker has circulated face counterclockwise one step

        Walker circulate_face_ccw() const;

        /// test if the walker has reached its initial halfedge

        bool full_circle() const;

        /// number of steps taken

        int no_steps() const;

        /// get ID of vertex pointed to by current halfedge of walker

        VertexID vertex() const; 

        /// get ID of face owning current halfedge of walker

        FaceID face() const; 

        /// get ID of current halfedge of walker

        HalfEdgeID halfedge() const;

        /// assignment operator

        Walker operator =(const Walker& w);

    private:

        const ConnectivityKernel* ck;

        HalfEdgeID current;

        HalfEdgeID last;

        int counter;

        Walker(const ConnectivityKernel& _ck, HalfEdgeID _current, HalfEdgeID _last, int _counter);

    };

    inline Walker::Walker(const ConnectivityKernel& _ck, HalfEdgeID _current) 

        : ck(&_ck), current(_current), last(_current), counter(0){}

    inline Walker::Walker(const ConnectivityKernel& _ck, HalfEdgeID _current, HalfEdgeID _last, int _counter)

        : ck(&_ck), current(_current), last(_last), counter(_counter){}

    inline Walker Walker::next() const

    { return Walker(*ck, ck->next(current), last, counter + 1); }

    inline Walker Walker::prev() const

    { return Walker(*ck, ck->prev(current), last, counter + 1); }

    inline Walker Walker::opp() const

    { return Walker(*ck, ck->opp(current), last, counter + 1); }

    inline Walker Walker::circulate_vertex_cw() const

    { return Walker(*ck, ck->next(ck->opp(current)), last, counter + 1); }

    inline Walker Walker::circulate_vertex_ccw() const

    { return Walker(*ck, ck->opp(ck->prev(current)), last, counter + 1); }

    inline Walker Walker::circulate_face_cw() const

    { return Walker(*ck, ck->prev(current), last, counter + 1); }

    inline Walker Walker::circulate_face_ccw() const

    { return Walker(*ck, ck->next(current), last, counter + 1); }

    inline bool Walker::full_circle() const

    { return (counter > 0 && current == last) ? true : false; }

    inline int Walker::no_steps() const

    { return counter; }

    inline VertexID Walker::vertex() const

    { return ck->vert(current); }

    inline FaceID Walker::face() const

    { return ck->face(current); }

    inline HalfEdgeID Walker::halfedge() const

    { return current; }

    inline Walker Walker::operator =(const Walker& w)

    { 

        current = w.current;

        counter = w.counter;

        ck = w.ck;

        last = w.last;

        return *this;

    }

}

#endif