/*******************************************************************************
* 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.opt;

import org.sat4j.core.VecInt;
import org.sat4j.specs.ContradictionException;
import org.sat4j.specs.IOptimizationProblem;
import org.sat4j.specs.ISolver;
import org.sat4j.specs.IVecInt;
import org.sat4j.specs.TimeoutException;
import org.sat4j.tools.SolverDecorator;

/**
 * Computes a solution with the smallest number of satisfied literals.
 *
 * Please make sure that newVar(howmany) is called first to setup the decorator.
 * 
 * @author leberre
 */
public class MinOneDecorator extends SolverDecorator<ISolver> implements
        IOptimizationProblem {

    /**
     * 
     */
    private static final long serialVersionUID = 1L;

    private int[] prevmodel;

    public MinOneDecorator(ISolver solver) {
        super(solver);
    }

    public boolean admitABetterSolution() throws TimeoutException {
        boolean result = isSatisfiable(true);
        if (result) {
            prevmodel = super.model();
        }
        return result;
    }

    public boolean hasNoObjectiveFunction() {
        return false;
    }

    public boolean nonOptimalMeansSatisfiable() {
        return true;
    }

    private int counter;

    public Number calculateObjective() {
        counter = 0;
        for (int p : prevmodel) {
            if (p > 0) {
                counter++;
            }
        }
        return new Integer(counter);
    }

    private final IVecInt literals = new VecInt();

    public void discard() throws ContradictionException {
        if (literals.isEmpty()) {
            for (int i = 1; i <= nVars(); i++) {
                literals.push(i);
            }
        }
        addAtMost(literals, counter - 1);
    }

    @Override
    public int[] model() {
     // DLB findbugs ok
        return prevmodel;
    }

    @Override
    public void reset() {
        literals.clear();
        super.reset();
    }

}