/*
* Hibernate, Relational Persistence for Idiomatic Java
*
* Copyright (c) 2008, Red Hat Middleware LLC or third-party contributors as
* indicated by the @author tags or express copyright attribution
* statements applied by the authors. All third-party contributions are
* distributed under license by Red Hat Middleware LLC.
*
* This copyrighted material is made available to anyone wishing to use, modify,
* copy, or redistribute it subject to the terms and conditions of the GNU
* Lesser General Public License, as published by the Free Software Foundation.
*
* 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 distribution; if not, write to:
* Free Software Foundation, Inc.
* 51 Franklin Street, Fifth Floor
* Boston, MA 02110-1301 USA
*/
package org.hibernate.envers.tools.graph;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
/**
* @author Adam Warski (adam at warski dot org)
*/
public class GraphTopologicalSort {
/**
* Sorts a graph topologically.
* @param definer Defines a graph (values and representations) to sort.
* @return Values of the graph, sorted topologically.
*/
public static <V, R> List<V> sort(GraphDefiner<V, R> definer) {
List<V> values = definer.getValues();
Map<R, Vertex<R>> vertices = new HashMap<R, Vertex<R>>();
// Creating a vertex for each representation
for (V v : values) {
R rep = definer.getRepresentation(v);
vertices.put(rep, new Vertex<R>(rep));
}
// Connecting neighbourhooding vertices
for (V v : values) {
for (V vn : definer.getNeighbours(v)) {
vertices.get(definer.getRepresentation(v)).addNeighbour(vertices.get(definer.getRepresentation(vn)));
}
}
// Sorting the representations
List<R> sortedReps = new TopologicalSort<R>().sort(vertices.values());
// Transforming the sorted representations to sorted values
List<V> sortedValues = new ArrayList<V>(sortedReps.size());
for (R rep : sortedReps) {
sortedValues.add(definer.getValue(rep));
}
return sortedValues;
}
}