/*******************************************************************************
* SAT4J: a SATisfiability library for Java Copyright (C) 2004-2008 Daniel Le Berre
*
* All rights reserved. This program and the accompanying materials
* are made available under the terms of the Eclipse Public License v1.0
* which accompanies this distribution, and is available at
* http://www.eclipse.org/legal/epl-v10.html
*
* Alternatively, the contents of this file may be used under the terms of
* either the GNU Lesser General Public License Version 2.1 or later (the
* "LGPL"), in which case the provisions of the LGPL are applicable instead
* of those above. If you wish to allow use of your version of this file only
* under the terms of the LGPL, and not to allow others to use your version of
* this file under the terms of the EPL, indicate your decision by deleting
* the provisions above and replace them with the notice and other provisions
* required by the LGPL. If you do not delete the provisions above, a recipient
* may use your version of this file under the terms of the EPL or the LGPL.
* 
* Based on the original MiniSat specification from:
* 
* An extensible SAT solver. Niklas Een and Niklas Sorensson. Proceedings of the
* Sixth International Conference on Theory and Applications of Satisfiability
* Testing, LNCS 2919, pp 502-518, 2003.
*
* See www.minisat.se for the original solver in C++.
* 
*******************************************************************************/
package org.sat4j.minisat.core;

import java.io.Serializable;

/**
 * Implementation of a queue.
 * 
 * Formerly used in the solver to maintain unit literals for unit propagation.
 * No longer used currently.
 * 
 * @author leberre
 */
public final class IntQueue implements Serializable {

    private static final long serialVersionUID = 1L;

    private static final int INITIAL_QUEUE_CAPACITY = 10;

    /**
     * Add an element to the queue. The queue is supposed to be large enough for
     * that!
     * 
     * @param x
     *            the element to add
     */
    public void insert(final int x) {
        // ensure(size + 1);
        assert size < myarray.length;
        myarray[size++] = x;
    }

    /**
     * returns the nexdt element in the queue. Unexpected results if the queue
     * is empty!
     * 
     * @return the firsst element on the queue
     */
    public int dequeue() {
        assert first < size;
        return myarray[first++];
    }

    /**
     * Vide la queue
     */
    public void clear() {
        size = 0;
        first = 0;
    }

    /**
     * Pour connaitre la taille de la queue.
     * 
     * @return le nombre d'elements restant dans la queue
     */
    public int size() {
        return size - first;
    }

    /**
     * Utilisee pour accroitre dynamiquement la taille de la queue.
     * 
     * @param nsize
     *            la taille maximale de la queue
     */
    public void ensure(final int nsize) {
        if (nsize >= myarray.length) {
            int[] narray = new int[Math.max(nsize, size * 2)];
            System.arraycopy(myarray, 0, narray, 0, size);
            myarray = narray;
        }
    }

    @Override
    public String toString() {
        StringBuffer stb = new StringBuffer();
        stb.append(">"); //$NON-NLS-1$
        for (int i = first; i < size - 1; i++) {
            stb.append(myarray[i]);
            stb.append(" "); //$NON-NLS-1$
        }
        if (first != size) {
            stb.append(myarray[size - 1]);
        }
        stb.append("<"); //$NON-NLS-1$
        return stb.toString();
    }

    private int[] myarray = new int[INITIAL_QUEUE_CAPACITY];

    private int size = 0;

    private int first = 0;

}