// This file is part of libigl, a simple c++ geometry processing library.
// 
// Copyright (C) 2015 Qingnan Zhou <qnzhou@gmail.com>
// 
// This Source Code Form is subject to the terms of the Mozilla Public License 
// v. 2.0. If a copy of the MPL was not distributed with this file, You can 
// obtain one at http://mozilla.org/MPL/2.0/.
//
#ifndef ORDER_FACETS_AROUND_EDGE_H
#define ORDER_FACETS_AROUND_EDGE_H
#include "../igl_inline.h"
#include <Eigen/Core>
#include <vector>

namespace igl {
    namespace cgal {
        // Given a directed edge, sort its adjacent faces.  Assuming the
        // directed edge is (s, d).  Sort the adjacent faces clockwise around the
        // axis (d - s), i.e. left-hand rule.  An adjacent face is consistently
        // oriented if it contains (d, s) as a directed edge.
        //
        // For overlapping faces, break the tie using signed face index, smaller
        // signed index comes before the larger signed index.  Signed index is
        // computed as (consistent? 1:-1) * (face_index + 1).
        //
        // Inputs:
        //   V          #V by 3 list of vertices.
        //   F          #F by 3 list of faces
        //   s          Index of source vertex.
        //   d          Index of desination vertex.
        //   adj_faces  List of adjacent face signed indices.
        //
        // Output:
        //   order      List of face indices that orders adjacent faces around
        //              edge (s, d) clockwise.
        template<
            typename DerivedV,
            typename DerivedF,
            typename DerivedI >
        IGL_INLINE
        void order_facets_around_edge(
                const Eigen::PlainObjectBase<DerivedV>& V,
                const Eigen::PlainObjectBase<DerivedF>& F,
                size_t s, size_t d, 
                const std::vector<int>& adj_faces,
                Eigen::PlainObjectBase<DerivedI>& order,
                bool debug=false);

        // This funciton is a wrapper around the one above.  Since the ordering
        // is circular, the pivot point is used to define a starting point.  So
        // order[0] is the index into adj_face that is immediately after the
        // pivot face (s, d, pivot point) in clockwise order.
        template<
            typename DerivedV,
            typename DerivedF,
            typename DerivedI>
        IGL_INLINE
        void order_facets_around_edge(
                const Eigen::PlainObjectBase<DerivedV>& V,
                const Eigen::PlainObjectBase<DerivedF>& F,
                size_t s, size_t d, 
                const std::vector<int>& adj_faces,
                const Eigen::PlainObjectBase<DerivedV>& pivot_point,
                Eigen::PlainObjectBase<DerivedI>& order);
    }
}

#ifndef IGL_STATIC_LIBRARY
#include "order_facets_around_edge.cpp"
#endif
#endif