/*******************************************************************************
    * 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.tools;
  
  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;
  
  public class OptToSatAdapter extends SolverDecorator<ISolver> {
  
      /**
       * 
       */
      private static final long serialVersionUID = 1L;
  
      IOptimizationProblem problem;
  
      boolean modelComputed = false;
      boolean optimalValueForced = false;
  
      public OptToSatAdapter(IOptimizationProblem problem) {
          super((ISolver) problem);
          this.problem = problem;
      }
  
      @Override
      public boolean isSatisfiable() throws TimeoutException {
          this.modelComputed = false;
          return this.problem.admitABetterSolution();
      }
  
      @Override
      public void reset() {
          super.reset();
          this.optimalValueForced = false;
      }
  
      @Override
      public boolean isSatisfiable(boolean global) throws TimeoutException {
          this.modelComputed = false;
          return this.problem.admitABetterSolution();
      }
  
      @Override
      public boolean isSatisfiable(IVecInt assumps, boolean global)
              throws TimeoutException {
          throw new UnsupportedOperationException();
      }
  
      @Override
      public boolean isSatisfiable(IVecInt assumps) throws TimeoutException {
          throw new UnsupportedOperationException();
      }
  
      @Override
      public int[] model() {
          if (this.modelComputed) {
              return this.problem.model();
          }
  
          try {
              assert this.problem.admitABetterSolution();
              do {
                  this.problem.discardCurrentSolution();
              } while (this.problem.admitABetterSolution());
              if (!this.optimalValueForced) {
                  try {
                      this.problem.forceObjectiveValueTo(this.problem
                              .getObjectiveValue());
                  } catch (ContradictionException e1) {
                     throw new IllegalStateException();
                 }
                 this.optimalValueForced = true;
             }
         } catch (TimeoutException e) {
             // solver timeout
         } catch (ContradictionException e) {
             // OK, optimal model found
             if (!this.optimalValueForced) {
                 try {
                     this.problem.forceObjectiveValueTo(this.problem
                             .getObjectiveValue());
                 } catch (ContradictionException e1) {
                     throw new IllegalStateException();
                 }
                 this.optimalValueForced = true;
             }
         }
         this.modelComputed = true;
         return this.problem.model();
     }
 
     @Override
     public boolean model(int var) {
         if (!this.modelComputed) {
             model();
         }
         return this.problem.model(var);
     }
 
     @Override
     public String toString(String prefix) {
         return prefix + "Optimization to SAT adapter\n"
                 + super.toString(prefix);
     }
 
     /**
      * Allow to easily check is the solution returned by isSatisfiable is
      * optimal or not.
      * 
      * @return true is the solution found is indeed optimal.
      */
     public boolean isOptimal() {
         return this.problem.isOptimal();
     }
 }