#ifndef TMeshEdge_hxx_seen
#define TMeshEdge_hxx_seen

#include <set>

namespace COMET {
    class IMesh;
    class IMeshPoint;
    class IMeshEdge;
};

class COMET::IMeshEdge {
    friend class IMesh;
    friend class IMeshPoint;
public:
    /// Create a new edge in the mesh.
    IMeshEdge(IMeshPoint* a, IMeshPoint* b);
    virtual ~IMeshEdge();

    /// Get the first mesh point in the edge.  This mesh point will be at a
    /// lesser X, or if the X is equal, a lesser Y coordinate.
    IMeshPoint* GetHead() const {return fHead;}
    
    /// Get the second point of the edge.
    IMeshPoint* GetTail() const {return fTail;}

    /// Get the other end of the edge.  This will return NULL if
    /// argument is not one of the points in the edge.
    IMeshPoint* GetOther(const IMeshPoint* a) const;

    /// Return the length of the edge in the abstract coordinate system.
    double GetLength(void) const;

    /// Return the length of the edge in the abstract coordinate system with
    /// scale factors applied.  These are multiplicative scale factors, and
    /// the length is calculated
    /// l=sqrt((xScale*(x1-x2))^2+(yScale*(y1-y2))^2).
    double GetLength(double xScale, double yScale) const;

    bool operator == (const IMeshEdge& rhs) const;

    bool operator < (const IMeshEdge& rhs) const;

private:
    /// The first mesh point in the edge.  This mesh point will be at a lesser
    /// X, or if the X is equal, a lesser Y coordinate.
    IMeshPoint* fHead;

    /// The second mesh point in the edge.
    IMeshPoint* fTail;
};

namespace COMET {
    struct TMeshEdgePointerLessThan {
        bool operator () (const COMET::IMeshEdge* a, 
                          const COMET::IMeshEdge* b) const {
            return *a < *b;
        }
    };
    typedef std::set<COMET::IMeshEdge*,COMET::TMeshEdgePointerLessThan> TMeshEdgeSet;
};

std::ostream& operator << (std::ostream& s, COMET::IMeshEdge& p);
#endif