/*******************************************************************************
    * 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.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 IConstr previousPBConstr;
      private IConstr addedConstr = null;
      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) {
              calculateObjective();
          } else {
              if (this.previousPBConstr != null) {
                  decorated().removeConstr(this.previousPBConstr);
                  this.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;
         }
         int maxValue = getObjectiveFunction().minValue().intValue();
         while (true) {
             if (this.addedConstr != null) {
                 this.decorated().removeConstr(this.addedConstr);
             }
             try {
                 forceObjectiveValueTo(maxValue++);
             } catch (ContradictionException e) {
                 if (isVerbose()) {
                     System.out.println(decorated().getLogPrefix()
                             + "no solution for objective value "
                             + (maxValue - 1));
                 }
                 continue;
             }
             isSatisfiable = super.isSatisfiable(assumps, true);
             if (isSatisfiable) {
                 this.optimumFound = true;
                 if (getObjectiveFunction() != null) {
                     calculateObjective();
                 }
                 this.decorated().removeConstr(this.addedConstr);
                 return true;
             }
             if (isVerbose()) {
                 System.out.println(decorated().getLogPrefix()
                         + "no solution for objective value " + (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");
         }
         this.objectiveValue = getObjectiveFunction().calculateDegree(this);
         return this.objectiveValue;
     }
 
     public Number getObjectiveValue() {
         return this.objectiveValue;
     }
 
     public void forceObjectiveValueTo(Number forcedValue)
             throws ContradictionException {
         this.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);
     }
 
     public void setTimeoutForFindingBetterSolution(int seconds) {
         throw new UnsupportedOperationException("Does not make sense here");
     }
 
 }