/*******************************************************************************
    * 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 pseudo boolean algorithms described in:
   * A fast pseudo-Boolean constraint solver Chai, D.; Kuehlmann, A.
   * Computer-Aided Design of Integrated Circuits and Systems, IEEE Transactions on
   * Volume 24, Issue 3, March 2005 Page(s): 305 - 317
   * 
   * and 
   * Heidi E. Dixon, 2004. Automating Pseudo-Boolean Inference within a DPLL 
   * Framework. Ph.D. Dissertation, University of Oregon.
   *******************************************************************************/
  package org.sat4j.pb;
  
  import java.math.BigInteger;
  
  import org.sat4j.core.VecInt;
  import org.sat4j.specs.ContradictionException;
  import org.sat4j.specs.IConstr;
  import org.sat4j.specs.IOptimizationProblem;
  import org.sat4j.specs.IVecInt;
  import org.sat4j.specs.TimeoutException;
  
  /**
   * 
   * @author lonca
   * 
   */
  
  public class ConstraintRelaxingPseudoOptDecorator extends PBSolverDecorator
  		implements IOptimizationProblem {
  
  	private static final long serialVersionUID = 1L;
  	private int[] bestModel;
  	private boolean[] bestFullModel;
  	private IConstr previousPBConstr;
  	private IConstr addedConstr = null;
  	private int maxValue = 0;
  	private Number objectiveValue;
  	private boolean optimumFound = false;
  
  	public ConstraintRelaxingPseudoOptDecorator(IPBSolver solver) {
  		super(solver);
  	}
  
  	@Override
  	public boolean isSatisfiable() throws TimeoutException {
  		return isSatisfiable(VecInt.EMPTY);
  	}
  
  	@Override
  	public boolean isSatisfiable(boolean global) throws TimeoutException {
  		return isSatisfiable(VecInt.EMPTY, global);
  	}
  
  	@Override
  	public boolean isSatisfiable(IVecInt assumps, boolean global)
  			throws TimeoutException {
  		boolean result = super.isSatisfiable(assumps, true);
  		if (result) {
  			bestModel = super.model();
  			bestFullModel = new boolean[nVars()];
  			for (int i = 0; i < nVars(); i++) {
  				bestFullModel[i] = decorated().model(i + 1);
  			}
  			calculateObjective();
  		} else {
  			if (previousPBConstr != null) {
  				decorated().removeConstr(previousPBConstr);
  				previousPBConstr = null;
  			}
  		}
  		return result;
  	}
  
  	@Override
  	public boolean isSatisfiable(IVecInt assumps) throws TimeoutException {
  		return isSatisfiable(assumps, true);
  	}
  
  	public boolean admitABetterSolution() throws TimeoutException {
  		return admitABetterSolution(VecInt.EMPTY);
  	}
  
 	public boolean admitABetterSolution(IVecInt assumps)
 			throws TimeoutException {
 		boolean isSatisfiable;
 
 		if (this.optimumFound) {
 			return false;
 		}
 		maxValue = getObjectiveFunction().minValue().intValue();
 		while (true) {
 			if (addedConstr != null) {
 				this.decorated().removeConstr(addedConstr);
 			}
 			try {
 				forceObjectiveValueTo(this.maxValue++);
 			} catch (ContradictionException e) {
 				if (isVerbose()) {
 					System.out.println(decorated().getLogPrefix()
 							+ "no solution for objective value "
 							+ (this.maxValue - 1));
 				}
 				continue;
 			}
 			isSatisfiable = super.isSatisfiable(assumps, true);
 			if (isSatisfiable) {
 				optimumFound = true;
 				bestModel = super.model();
 				bestFullModel = new boolean[nVars()];
 				for (int i = 0; i < nVars(); i++) {
 					bestFullModel[i] = decorated().model(i + 1);
 				}
 				if (getObjectiveFunction() != null) {
 					calculateObjective();
 				}
 				this.decorated().removeConstr(addedConstr);
 				return true;
 			}
 			if (isVerbose()) {
 				System.out.println(decorated().getLogPrefix()
 						+ "no solution for objective value "
 						+ (this.maxValue - 1));
 			}
 		}
 	}
 
 	public boolean hasNoObjectiveFunction() {
 		return getObjectiveFunction() == null;
 	}
 
 	public boolean nonOptimalMeansSatisfiable() {
 		return false;
 	}
 
 	@Deprecated
 	public Number calculateObjective() {
 		if (getObjectiveFunction() == null) {
 			throw new UnsupportedOperationException(
 					"The problem does not contain an objective function");
 		}
 		objectiveValue = getObjectiveFunction().calculateDegree(this);
 		return objectiveValue;
 	}
 
 	public Number getObjectiveValue() {
 		return objectiveValue;
 	}
 
 	public void forceObjectiveValueTo(Number forcedValue)
 			throws ContradictionException {
 		addedConstr = super.addPseudoBoolean(getObjectiveFunction().getVars(),
 				getObjectiveFunction().getCoeffs(), false,
 				BigInteger.valueOf(forcedValue.longValue()));
 	}
 
 	@Deprecated
 	public void discard() {
 		discardCurrentSolution();
 	}
 
 	public void discardCurrentSolution() {
 		// nothing to do here
 	}
 
 	public boolean isOptimal() {
 		return this.optimumFound;
 	}
 
 	@Override
 	public String toString(String prefix) {
 		return prefix + "Pseudo Boolean Optimization by lower bound\n"
 				+ super.toString(prefix);
 	}
 
 }