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/**
 * Copyright (C) 2008, University of Manchester
 *
 * Modifications to the initial code base are copyright of their
 * respective authors, or their employers as appropriate.  Authorship
 * of the modifications may be determined from the ChangeLog placed at
 * the end of this file.
 *
 * This library 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 2.1 of the License, or (at your option) any later version.

 * This library 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 library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 */
package org.coode.oppl.utils;

import static org.coode.oppl.utils.ArgCheck.checkNotNull;

import java.util.ArrayList;
import java.util.Collection;
import java.util.HashSet;
import java.util.List;
import java.util.Set;

import org.coode.oppl.search.SearchTree;

class PermutationState {
    private final Collection referenceCollection;
    private final List sequence = new ArrayList();
    private final boolean isGoal;

    /** @param referenceCollection
     *            referenceCollection
     * @param sequence
     *            sequence */
    PermutationState(Collection referenceCollection, List sequence) {
        this.referenceCollection = checkNotNull(referenceCollection,
                "referenceCollection");
        this.sequence.addAll(sequence);
        this.isGoal = referenceCollection.size() == this.getSequence().size();
    }

    /** @return the referenceCollection */
    public Collection getReferenceCollection() {
        return this.referenceCollection;
    }

    /** @return the isGoal */
    public boolean isGoal() {
        return this.isGoal;
    }

    /** @return the sequence */
    public List getSequence() {
        return this.sequence;
    }
}

/** @author Luigi Iannone
 * @param 
 *            type */
public class CollectionPermutation extends SearchTree> {
    private CollectionPermutation() {}

    @Override
    protected List> getChildren(PermutationState node) {
        List> toReturn = new ArrayList>();
        Collection remainder = new HashSet(node.getReferenceCollection());
        remainder.removeAll(node.getSequence());
        for (N n : remainder) {
            List newSequence = new ArrayList(node.getSequence());
            newSequence.add(n);
            toReturn.add(new PermutationState(node.getReferenceCollection(),
                    newSequence));
        }
        return toReturn;
    }

    @Override
    protected boolean goalReached(PermutationState node) {
        return node.isGoal();
    }

    /** @param collection
     *            collection
     * @param 
     *            collection type
     * @return all permutations */
    public static  Set> getAllPermutations(Collection collection) {
        CollectionPermutation setPermutation = new CollectionPermutation();
        Set> toReturn = new HashSet>();
        List>> solutions = new ArrayList>>();
        setPermutation.exhaustiveSearchTree(new PermutationState(collection,
                new ArrayList()), solutions);
        for (List> solution : solutions) {
            toReturn.add(solution.get(solution.size() - 1).getSequence());
        }
        return toReturn;
    }
}