/*******************************************************************************
    * 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.VecInt;
  import org.sat4j.specs.ContradictionException;
  import org.sat4j.specs.IConstr;
  import org.sat4j.specs.IOptimizationProblem;
  import org.sat4j.specs.ISolver;
  import org.sat4j.specs.IVecInt;
  import org.sat4j.specs.TimeoutException;
  import org.sat4j.tools.SolverDecorator;
  
  /**
   * Computes a solution with the smallest number of satisfied literals.
   * 
   * Please make sure that newVar(howmany) is called first to setup the decorator.
   * 
   * @author leberre
   */
  public final class MinOneDecorator extends SolverDecorator<ISolver> implements
          IOptimizationProblem {
  
      /**
       * 
       */
      private static final long serialVersionUID = 1L;
  
      private int[] prevmodel;
  
      private boolean isSolutionOptimal;
  
      public MinOneDecorator(ISolver solver) {
          super(solver);
      }
  
      public boolean admitABetterSolution() throws TimeoutException {
          return admitABetterSolution(VecInt.EMPTY);
      }
  
      /**
       * @since 2.1
       */
      public boolean admitABetterSolution(IVecInt assumps)
              throws TimeoutException {
          this.isSolutionOptimal = false;
          boolean result = isSatisfiable(assumps, true);
          if (result) {
              this.prevmodel = super.model();
              calculateObjectiveValue();
          } else {
              this.isSolutionOptimal = true;
          }
          return result;
      }
  
      public boolean hasNoObjectiveFunction() {
          return false;
      }
  
      public boolean nonOptimalMeansSatisfiable() {
          return true;
      }
  
      private int counter;
  
      public Number calculateObjective() {
          calculateObjectiveValue();
          return this.counter;
      }
  
      private void calculateObjectiveValue() {
         this.counter = 0;
         for (int p : this.prevmodel) {
             if (p > 0) {
                 this.counter++;
             }
         }
     }
 
     private final IVecInt literals = new VecInt();
 
     private IConstr previousConstr;
 
     /**
      * @since 2.1
      */
     public void discardCurrentSolution() throws ContradictionException {
         if (this.literals.isEmpty()) {
             for (int i = 1; i <= nVars(); i++) {
                 this.literals.push(i);
             }
         }
         if (this.previousConstr != null) {
             super.removeConstr(this.previousConstr);
         }
         this.previousConstr = addAtMost(this.literals, this.counter - 1);
     }
 
     @Override
     public int[] model() {
         // DLB findbugs ok
         return this.prevmodel;
     }
 
     @Override
     public void reset() {
         this.literals.clear();
         this.previousConstr = null;
         super.reset();
     }
 
     /**
      * @since 2.1
      */
     public Number getObjectiveValue() {
         return this.counter;
     }
 
     public void discard() throws ContradictionException {
         discardCurrentSolution();
     }
 
     /**
      * @since 2.1
      */
     public void forceObjectiveValueTo(Number forcedValue)
             throws ContradictionException {
         try {
             addAtMost(this.literals, forcedValue.intValue());
         } catch (ContradictionException ce) {
             this.isSolutionOptimal = true;
             throw ce;
         }
 
     }
 
     public boolean isOptimal() {
         return this.isSolutionOptimal;
     }
 }