/*******************************************************************************
    * 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.minisat.constraints.cnf;
  
  import org.sat4j.core.LiteralsUtils;
  import org.sat4j.minisat.core.Constr;
  import org.sat4j.minisat.core.ILits;
  import org.sat4j.specs.IVecInt;
  import org.sat4j.specs.UnitPropagationListener;
  
  /**
   * 
   * @author daniel
   * @since 2.1
   */
  public class UnitClause implements Constr {
  
      protected final int literal;
      protected double activity;
  
      public UnitClause(int value) {
          this.literal = value;
      }
  
      public void assertConstraint(UnitPropagationListener s) {
          s.enqueue(this.literal, this);
      }
  
      public void assertConstraintIfNeeded(UnitPropagationListener s) {
          assertConstraint(s);
      }
  
      public void calcReason(int p, IVecInt outReason) {
          if (p == ILits.UNDEFINED) {
              outReason.push(LiteralsUtils.neg(this.literal));
          }
      }
  
      public double getActivity() {
          return activity;
      }
  
      public void incActivity(double claInc) {
          // silent to prevent problems with xplain trick.
      }
  
      public void setActivity(double claInc) {
          activity = claInc;
      }
  
      public boolean locked() {
          throw new UnsupportedOperationException();
      }
  
      public void register() {
          throw new UnsupportedOperationException();
      }
  
      public void remove(UnitPropagationListener upl) {
          upl.unset(this.literal);
      }
  
      public void rescaleBy(double d) {
          throw new UnsupportedOperationException();
      }
  
      public void setLearnt() {
          throw new UnsupportedOperationException();
      }
  
      public boolean simplify() {
          return false;
     }
 
     public boolean propagate(UnitPropagationListener s, int p) {
         throw new UnsupportedOperationException();
     }
 
     public int get(int i) {
         if (i > 0) {
             throw new IllegalArgumentException();
         }
         return this.literal;
     }
 
     public boolean learnt() {
         return false;
     }
 
     public int size() {
         return 1;
     }
 
     public void forwardActivity(double claInc) {
         // silent to prevent problems with xplain trick.
     }
 
     @Override
     public String toString() {
         return Lits.toString(this.literal);
     }
 
     public boolean canBePropagatedMultipleTimes() {
         return false;
     }
 
     public void calcReasonOnTheFly(int p, IVecInt trail, IVecInt outReason) {
         calcReason(p, outReason);
     }
 }