/*******************************************************************************
    * 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.IConstr;
  import org.sat4j.specs.ISolver;
  import org.sat4j.specs.IVecInt;
  import org.sat4j.specs.TimeoutException;
  
  /**
   * Computes a solution that satisfies the maximum of clauses.
   * 
   * @author daniel
   * 
   */
  public final class MaxSatDecorator extends AbstractSelectorVariablesDecorator {
  
  	/**
       * 
       */
  	private static final long serialVersionUID = 1L;
  
  	public MaxSatDecorator(ISolver solver) {
  		super(solver);
  	}
  
  	@Override
  	public void setExpectedNumberOfClauses(int nb) {
  		super.setExpectedNumberOfClauses(nb);
  		lits.ensure(nb);
  	}
  
  	@Override
  	public IConstr addClause(IVecInt literals) throws ContradictionException {
  		int newvar = nextFreeVarId(true);
  		lits.push(newvar);
  		literals.push(newvar);
  		return super.addClause(literals);
  	}
  
  	@Override
  	public void reset() {
  		lits.clear();
  		super.reset();
  		prevConstr = null;
  	}
  
  	public boolean hasNoObjectiveFunction() {
  		return false;
  	}
  
  	public boolean nonOptimalMeansSatisfiable() {
  		return false;
  	}
  
  	public Number calculateObjective() {
  		calculateObjectiveValue();
  		return counter;
  	}
  
  	private final IVecInt lits = new VecInt();
  
  	private int counter;
  
  	private IConstr prevConstr;
  
  	/**
  	 * @since 2.1
  	 */
  	public void discardCurrentSolution() throws ContradictionException {
  		if (prevConstr != null) {
  			super.removeSubsumedConstr(prevConstr);
 		}
 		try {
 			prevConstr = super.addAtMost(lits, counter - 1);
 		} catch (ContradictionException ce) {
 			isSolutionOptimal = true;
 			throw ce;
 		}
 	}
 
 	@Override
 	public boolean admitABetterSolution(IVecInt assumps)
 			throws TimeoutException {
 
 		boolean result = super.admitABetterSolution(assumps);
 		if (!result) {
 			if (prevConstr != null) {
 				super.removeConstr(prevConstr);
 				prevConstr = null;
 			}
 		}
 		return result;
 	}
 
 	public void discard() throws ContradictionException {
 		discardCurrentSolution();
 	}
 
 	/**
 	 * @since 2.1
 	 */
 	public Number getObjectiveValue() {
 		return counter;
 	}
 
 	@Override
 	void calculateObjectiveValue() {
 		counter = 0;
 		for (int q : prevfullmodel) {
 			if (q > nVars()) {
 				counter++;
 			}
 		}
 	}
 
 	/**
 	 * @since 2.1
 	 */
 	public void forceObjectiveValueTo(Number forcedValue)
 			throws ContradictionException {
 		super.addAtMost(lits, forcedValue.intValue());
 	}
 
 }