/*******************************************************************************
    * 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 java.io.Serializable;
  
  import org.sat4j.minisat.core.Constr;
  import org.sat4j.minisat.core.ILits;
  import org.sat4j.minisat.core.Propagatable;
  import org.sat4j.specs.IVecInt;
  import org.sat4j.specs.UnitPropagationListener;
  
  /**
   * Lazy data structure for clause using Watched Literals.
   * 
   * @author leberre
   */
  public abstract class WLClause implements Propagatable, Constr, Serializable {
  
      private static final long serialVersionUID = 1L;
  
      /**
       * @since 2.1
       */
      protected double activity;
  
      protected final int[] lits;
  
      protected final ILits voc;
  
      /**
       * Creates a new basic clause
       * 
       * @param voc
       *            the vocabulary of the formula
       * @param ps
       *            A VecInt that WILL BE EMPTY after calling that method.
       */
      public WLClause(IVecInt ps, ILits voc) {
          this.lits = new int[ps.size()];
          ps.moveTo(this.lits);
          assert ps.size() == 0;
          this.voc = voc;
          this.activity = 0;
      }
  
      /*
       * (non-Javadoc)
       * 
       * @see Constr#calcReason(Solver, Lit, Vec)
       */
      public void calcReason(int p, IVecInt outReason) {
          // assert outReason.size() == 0
          // && ((p == ILits.UNDEFINED) || (p == lits[0]));
          final int[] mylits = this.lits;
          for (int i = p == ILits.UNDEFINED ? 0 : 1; i < mylits.length; i++) {
              assert this.voc.isFalsified(mylits[i]);
              outReason.push(mylits[i] ^ 1);
          }
      }
  
      /**
       * @since 2.1
       */
      public void remove(UnitPropagationListener upl) {
          this.voc.watches(this.lits[0] ^ 1).remove(this);
          this.voc.watches(this.lits[1] ^ 1).remove(this);
          // la clause peut etre effacee
      }
  
      /*
       * (non-Javadoc)
      * 
      * @see Constr#simplify(Solver)
      */
     public boolean simplify() {
         for (int lit : this.lits) {
             if (this.voc.isSatisfied(lit)) {
                 return true;
             }
         }
         return false;
     }
 
     public boolean propagate(UnitPropagationListener s, int p) {
         final int[] mylits = this.lits;
         // Lits[1] must contain a falsified literal
         if (mylits[0] == (p ^ 1)) {
             mylits[0] = mylits[1];
             mylits[1] = p ^ 1;
         }
         // assert mylits[1] == (p ^ 1);
         int previous = p ^ 1, tmp;
         // look for new literal to watch: applying move to front strategy
         for (int i = 2; i < mylits.length; i++) {
             if (this.voc.isFalsified(mylits[i])) {
                 tmp = previous;
                 previous = mylits[i];
                 mylits[i] = tmp;
             } else {
                 mylits[1] = mylits[i];
                 mylits[i] = previous;
                 this.voc.watch(mylits[1] ^ 1, this);
                 return true;
             }
         }
         // assert voc.isFalsified(mylits[1]);
         // the clause is now either unit or null
         // move back the literals to their initial position
         System.arraycopy(mylits, 2, mylits, 1, mylits.length - 2);
         mylits[mylits.length - 1] = previous;
         this.voc.watch(p, this);
         // propagates first watched literal
         return s.enqueue(mylits[0], this);
     }
 
     /*
      * For learnt clauses only @author leberre
      */
     public boolean locked() {
         return this.voc.getReason(this.lits[0]) == this;
     }
 
     /**
      * @return the activity of the clause
      */
     public double getActivity() {
         return this.activity;
     }
 
     public void setActivity(double d) {
         this.activity = d;
     }
 
     @Override
     public String toString() {
         StringBuffer stb = new StringBuffer();
         for (int lit : this.lits) {
             stb.append(Lits.toString(lit));
             stb.append("["); //$NON-NLS-1$
             stb.append(this.voc.valueToString(lit));
             stb.append("]"); //$NON-NLS-1$
             stb.append(" "); //$NON-NLS-1$
         }
         return stb.toString();
     }
 
     /**
      * Retourne le ieme literal de la clause. Attention, cet ordre change durant
      * la recherche.
      * 
      * @param i
      *            the index of the literal
      * @return the literal
      */
     public int get(int i) {
         return this.lits[i];
     }
 
     /**
      * @param d
      */
     public void rescaleBy(double d) {
         this.activity *= d;
     }
 
     public int size() {
         return this.lits.length;
     }
 
     public void assertConstraint(UnitPropagationListener s) {
         boolean ret = s.enqueue(this.lits[0], this);
         assert ret;
     }
 
     public void assertConstraintIfNeeded(UnitPropagationListener s) {
         if (voc.isFalsified(this.lits[1])) {
             boolean ret = s.enqueue(this.lits[0], this);
             assert ret;
         }
     }
 
     public ILits getVocabulary() {
         return this.voc;
     }
 
     public int[] getLits() {
         int[] tmp = new int[size()];
         System.arraycopy(this.lits, 0, tmp, 0, size());
         return tmp;
     }
 
     @Override
     public boolean equals(Object obj) {
         if (obj == null) {
             return false;
         }
         try {
             WLClause wcl = (WLClause) obj;
             if (this.lits.length != wcl.lits.length) {
                 return false;
             }
             boolean ok;
             for (int lit : this.lits) {
                 ok = false;
                 for (int lit2 : wcl.lits) {
                     if (lit == lit2) {
                         ok = true;
                         break;
                     }
                 }
                 if (!ok) {
                     return false;
                 }
             }
             return true;
         } catch (ClassCastException e) {
             return false;
         }
     }
 
     @Override
     public int hashCode() {
         long sum = 0;
         for (int p : this.lits) {
             sum += p;
         }
         return (int) sum / this.lits.length;
     }
 
     public boolean canBePropagatedMultipleTimes() {
         return false;
     }
 
     public Constr toConstraint() {
         return this;
     }
 
     public void calcReasonOnTheFly(int p, IVecInt trail, IVecInt outReason) {
         calcReason(p, outReason);
     }
 }