/*******************************************************************************
    * 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.ConstrGroup;
  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;
  
      private final boolean equivalence;
  
      public MaxSatDecorator(ISolver solver) {
          this(solver, false);
      }
  
      public MaxSatDecorator(ISolver solver, boolean equivalence) {
          super(solver);
          this.equivalence = equivalence;
      }
  
      @Override
      public void setExpectedNumberOfClauses(int nb) {
          super.setExpectedNumberOfClauses(nb);
          this.lits.ensure(nb);
      }
  
      @Override
      public IConstr addClause(IVecInt literals) throws ContradictionException {
          int newvar = nextFreeVarId(true);
          this.lits.push(newvar);
          literals.push(newvar);
          if (this.equivalence) {
              ConstrGroup constrs = new ConstrGroup();
              constrs.add(super.addClause(literals));
              IVecInt clause = new VecInt(2);
              clause.push(-newvar);
              for (int i = 0; i < literals.size() - 1; i++) {
                  clause.push(-literals.get(i));
                  constrs.add(super.addClause(clause));
              }
              clause.pop();
              return constrs;
          }
          return super.addClause(literals);
      }
  
      @Override
      public void reset() {
          this.lits.clear();
          super.reset();
          this.prevConstr = null;
      }
  
      public boolean hasNoObjectiveFunction() {
          return false;
      }
 
     public boolean nonOptimalMeansSatisfiable() {
         return false;
     }
 
     public Number calculateObjective() {
         calculateObjectiveValue();
         return this.counter;
     }
 
     private final IVecInt lits = new VecInt();
 
     private int counter;
 
     private IConstr prevConstr;
 
     /**
      * @since 2.1
      */
     public void discardCurrentSolution() throws ContradictionException {
         if (this.prevConstr != null) {
             super.removeSubsumedConstr(this.prevConstr);
         }
         try {
             this.prevConstr = super.addAtMost(this.lits, this.counter - 1);
         } catch (ContradictionException ce) {
             this.isSolutionOptimal = true;
             throw ce;
         }
     }
 
     @Override
     public boolean admitABetterSolution(IVecInt assumps)
             throws TimeoutException {
 
         boolean result = super.admitABetterSolution(assumps);
         if (!result) {
             if (this.prevConstr != null) {
                 super.removeConstr(this.prevConstr);
                 this.prevConstr = null;
             }
         }
         return result;
     }
 
     public void discard() throws ContradictionException {
         discardCurrentSolution();
     }
 
     /**
      * @since 2.1
      */
     public Number getObjectiveValue() {
         return this.counter;
     }
 
     @Override
     void calculateObjectiveValue() {
         this.counter = 0;
         for (int q : this.prevfullmodel) {
             if (q > nVars()) {
                 this.counter++;
             }
         }
     }
 
     /**
      * @since 2.1
      */
     public void forceObjectiveValueTo(Number forcedValue)
             throws ContradictionException {
         super.addAtMost(this.lits, forcedValue.intValue());
     }
 
 }