/*******************************************************************************
 * SAT4J: a SATisfiability library for Java Copyright (C) 2004, 2012 Artois University and CNRS
 *
 * 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++.
 *
 * Contributors:
 *   CRIL - initial API and implementation
 *******************************************************************************/
package org.sat4j.opt;

import org.sat4j.core.VecInt;
import org.sat4j.specs.ContradictionException;
import org.sat4j.specs.IConstr;
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 final class MinOneDecorator extends SolverDecorator<ISolver> implements
        IOptimizationProblem {

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

    private int[] prevmodel;
    private int[] prevmodelWithInternalVariables;

    private boolean isSolutionOptimal;

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

    public boolean admitABetterSolution() throws TimeoutException {
        return admitABetterSolution(VecInt.EMPTY);
    }

    /**
     * @since 2.1
     */
    public boolean admitABetterSolution(IVecInt assumps)
            throws TimeoutException {
        this.isSolutionOptimal = false;
        boolean result = isSatisfiable(assumps, true);
        if (result) {
            this.prevmodel = super.model();
            this.prevmodelWithInternalVariables = super
                    .modelWithInternalVariables();
            calculateObjectiveValue();
        } else {
            this.isSolutionOptimal = true;
        }
        return result;
    }

    public boolean hasNoObjectiveFunction() {
        return false;
    }

    public boolean nonOptimalMeansSatisfiable() {
        return true;
    }

    private int counter;

    public Number calculateObjective() {
        calculateObjectiveValue();
        return this.counter;
    }

    private void calculateObjectiveValue() {
        this.counter = 0;
        for (int p : this.prevmodel) {
            if (p > 0) {
                this.counter++;
            }
        }
    }

    private final IVecInt literals = new VecInt();

    private IConstr previousConstr;

    /**
     * @since 2.1
     */
    public void discardCurrentSolution() throws ContradictionException {
        if (this.literals.isEmpty()) {
            for (int i = 1; i <= nVars(); i++) {
                this.literals.push(i);
            }
        }
        if (this.previousConstr != null) {
            super.removeConstr(this.previousConstr);
        }
        this.previousConstr = addAtMost(this.literals, this.counter - 1);
    }

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

    @Override
    public int[] modelWithInternalVariables() {
        return this.prevmodelWithInternalVariables;
    }

    @Override
    public void reset() {
        this.literals.clear();
        this.previousConstr = null;
        super.reset();
    }

    /**
     * @since 2.1
     */
    public Number getObjectiveValue() {
        return this.counter;
    }

    public void discard() throws ContradictionException {
        discardCurrentSolution();
    }

    /**
     * @since 2.1
     */
    public void forceObjectiveValueTo(Number forcedValue)
            throws ContradictionException {
        try {
            addAtMost(this.literals, forcedValue.intValue());
        } catch (ContradictionException ce) {
            this.isSolutionOptimal = true;
            throw ce;
        }

    }

    public boolean isOptimal() {
        return this.isSolutionOptimal;
    }

    public void setTimeoutForFindingBetterSolution(int seconds) {
        // TODO
        throw new UnsupportedOperationException("No implemented yet");
    }
}
