IncidentEdgeCompare.java

/**
 Ported by David Turner from Visilibity, by Karl J. Obermeyer
   
 
 This port undoubtedly introduced a number of bugs (and removed some features).
 
 Bug reports should be directed to the OpenTripPlanner project, unless they 
 can be reproduced in the original VisiLibity.
  
 This program is free software: you can redistribute it and/or modify it under
 the terms of the GNU Lesser General Public License as published by the
 Free Software Foundation, either version 3 of the License, or (at your
 option) any later version.

 This program is distributed in the hope that it will be useful, but WITHOUT
 ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public
 License for more details.

 You should have received a copy of the GNU Lesser General Public
 License along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

package org.opentripplanner.visibility;

import java.util.Comparator;

/**
 * This is *reversed* from the original since Java PQs are min-heaps while STL PQs are max-heaps
 * 
 */
class IncidentEdgeCompare implements Comparator<PolarEdge> {
    VLPoint observer_pointer;

    PolarPointWithEdgeInfo current_vertex_pointer;

    double epsilon;

    public IncidentEdgeCompare(VLPoint observer, PolarPointWithEdgeInfo current_vertex,
            double epsilon_temp) {

        observer_pointer = observer;
        current_vertex_pointer = current_vertex;
        epsilon = epsilon_temp;
    }

    public int compare(PolarEdge e1, PolarEdge e2) {
        PolarPoint k1, k2;
        LineSegment xing1 = new Ray(observer_pointer, current_vertex_pointer.bearing).intersection(
                new LineSegment(e1.first, e1.second), epsilon);

        LineSegment xing2 = new Ray(observer_pointer, current_vertex_pointer.bearing).intersection(
                new LineSegment(e2.first, e2.second), epsilon);
        if (xing1.size() > 0 && xing2.size() > 0) {
            k1 = new PolarPoint(observer_pointer, xing1.first());
            k2 = new PolarPoint(observer_pointer, xing2.first());
            return (int) Math.signum(k1.range - k2.range);
        }
        // Otherwise infeasible edges are given lower priority, so they
        // get pushed out the top of the priority_queue's (q2's)
        // heap.
        else if (xing1.size() == 0 && xing2.size() > 0)
            return -1;
        else if (xing1.size() > 0 && xing2.size() == 0)
            return 1;
        else
            return 0;
    }
}