/*******************************************************************************
    * 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.card;
  
  import java.io.Serializable;
  
  import org.sat4j.minisat.constraints.cnf.Lits;
  import org.sat4j.minisat.constraints.cnf.UnitClauses;
  import org.sat4j.minisat.core.Constr;
  import org.sat4j.minisat.core.ILits;
  import org.sat4j.minisat.core.Propagatable;
  import org.sat4j.minisat.core.Undoable;
  import org.sat4j.minisat.core.UnitPropagationListener;
  import org.sat4j.specs.ContradictionException;
  import org.sat4j.specs.IVecInt;
  
  public class MinWatchCard implements Propagatable, Constr, Undoable,
          Serializable {
  
      private static final long serialVersionUID = 1L;
  
      public static final boolean ATLEAST = true;
  
      public static final boolean ATMOST = false;
  
      /**
       * degree of the cardinality constraint
       */
      protected int degree;
  
      /**
       * literals involved in the constraint
       */
      private final int[] lits;
  
      /**
       * contains the sign of the constraint : ATLEAT or ATMOST
       */
      private boolean moreThan;
  
      /**
       * contains the sum of the coefficients of the watched literals
       */
      protected int watchCumul;
  
      /**
       * Vocabulary of the constraint
       */
      private final ILits voc;
  
      /**
       * Constructs and normalizes a cardinality constraint. used by
       * minWatchCardNew in the non-normalized case.
       * 
       * @param voc
       *            vocabulary used by the constraint
       * @param ps
       *            literals involved in the constraint
       * @param moreThan
       *            should be ATLEAST or ATMOST;
       * @param degree
       *            degree of the constraint
       */
      public MinWatchCard(ILits voc, IVecInt ps, boolean moreThan, int degree) {
          // On met en place les valeurs
          this.voc = voc;
          this.degree = degree;
          this.moreThan = moreThan;
  
          // On simplifie ps
          int[] index = new int[voc.nVars() * 2 + 2];
          // Fresh array should have all elements set to 0
 
         // On repertorie les litt?raux utiles
         for (int i = 0; i < ps.size(); i++) {
             int p = ps.get(i);
             if (index[p ^ 1] == 0) {
                 index[p]++;
             } else {
                 index[p ^ 1]--;
             }
         }
         // On supprime les litt?raux inutiles
         int ind = 0;
         while (ind < ps.size()) {
             if (index[ps.get(ind)] > 0) {
                 index[ps.get(ind)]--;
                 ind++;
             } else {
                 // ??
                 if ((ps.get(ind) & 1) != 0) {
                     this.degree--;
                 }
                 ps.delete(ind);
             }
         }
 
         // On copie les litt?raux de la contrainte
         this.lits = new int[ps.size()];
         ps.moveTo(this.lits);
 
         // On normalise la contrainte au sens de Barth
         normalize();
 
     }
 
     /**
      * Constructs and normalizes a cardinality constraint. used by
      * MinWatchCardPB.normalizedMinWatchCardNew() in the normalized case. <br />
      * <strong>Should not be used if parameters are not already
      * normalized</strong><br />
      * This constraint is always an ATLEAST constraint.
      * 
      * @param voc
      *            vocabulary used by the constraint
      * @param ps
      *            literals involved in the constraint
      * @param degree
      *            degree of the constraint
      */
     protected MinWatchCard(ILits voc, IVecInt ps, int degree) {
         // On met en place les valeurs
         this.voc = voc;
         this.degree = degree;
         this.moreThan = ATLEAST;
 
         // On copie les litt?raux de la contrainte
         this.lits = new int[ps.size()];
         ps.moveTo(this.lits);
 
     }
 
     /**
      * computes the reason for a literal
      * 
      * @param p
      *            falsified literal (or Lit.UNDEFINED)
      * @param outReason
      *            the reason to be computed. Vector of literals.
      * @see Constr#calcReason(int p, IVecInt outReason)
      */
     public void calcReason(int p, IVecInt outReason) {
         for (int lit : this.lits) {
             if (this.voc.isFalsified(lit)) {
                 outReason.push(lit ^ 1);
             }
         }
     }
 
     /**
      * Returns the activity of the constraint
      * 
      * @return activity value of the constraint
      * @see Constr#getActivity()
      */
     public double getActivity() {
         return 0;
     }
 
     /**
      * Increments activity of the constraint
      * 
      * @param claInc
      *            value to be added to the activity of the constraint
      * @see Constr#incActivity(double claInc)
      */
     public void incActivity(double claInc) {
     }
 
     public void setActivity(double d) {
     }
 
     /**
      * Returns wether the constraint is learnt or not.
      * 
      * @return false : a MinWatchCard cannot be learnt.
      * @see Constr#learnt()
      */
     public boolean learnt() {
         return false;
     }
 
     /**
      * Simplifies the constraint w.r.t. the assignments of the literals
      * 
      * @param voc
      *            vocabulary used
      * @param ps
      *            literals involved
      * @return value to be added to the degree. This value is less than or equal
      *         to 0.
      */
     protected static int linearisation(ILits voc, IVecInt ps) {
         // Stockage de l'influence des modifications
         int modif = 0;
 
         for (int i = 0; i < ps.size();) {
             // on verifie si le litteral est affecte
             if (voc.isUnassigned(ps.get(i))) {
                 i++;
             } else {
                 // Si le litteral est satisfait,
                 // ?a revient ? baisser le degr?
                 if (voc.isSatisfied(ps.get(i))) {
                     modif--;
                 }
                 // dans tous les cas, s'il est assign?,
                 // on enleve le ieme litteral
                 ps.set(i, ps.last());
                 ps.pop();
             }
         }
 
         // DLB: inutile?
         // ps.shrinkTo(nbElement);
         assert modif <= 0;
 
         return modif;
     }
 
     /**
      * Returns if the constraint is the reason for a unit propagation.
      * 
      * @return true
      * @see Constr#locked()
      */
     public boolean locked() {
         return true;
     }
 
     /**
      * Constructs a cardinality constraint with a minimal set of watched
      * literals Permet la cr?ation de contrainte de cardinalit? ? observation
      * minimale
      * 
      * @param s
      *            tool for propagation
      * @param voc
      *            vocalulary used by the constraint
      * @param ps
      *            literals involved in the constraint
      * @param moreThan
      *            sign of the constraint. Should be ATLEAST or ATMOST.
      * @param degree
      *            degree of the constraint
      * @return a new cardinality constraint, null if it is a tautology
      * @throws ContradictionException
      */
     public static Constr minWatchCardNew(UnitPropagationListener s, ILits voc,
             IVecInt ps, boolean moreThan, int degree)
             throws ContradictionException {
 
         int mydegree = degree + linearisation(voc, ps);
 
         if (ps.size() < mydegree) {
             throw new ContradictionException();
         } else if (ps.size() == mydegree) {
             for (int i = 0; i < ps.size(); i++) {
                 if (!s.enqueue(ps.get(i))) {
                     throw new ContradictionException();
                 }
             }
             return new UnitClauses(ps);
         }
 
         // La contrainte est maintenant cr??e
         MinWatchCard retour = new MinWatchCard(voc, ps, moreThan, mydegree);
 
         if (retour.degree <= 0) {
             return null;
         }
 
         retour.computeWatches();
 
         retour.computePropagation(s);
 
         return retour;
     }
 
     /**
      * normalize the constraint (cf. P.Barth normalization)
      */
     public final void normalize() {
         // Gestion du signe
         if (!this.moreThan) {
             // On multiplie le degr? par -1
             this.degree = 0 - this.degree;
             // On r?vise chaque litt?ral
             for (int indLit = 0; indLit < this.lits.length; indLit++) {
                 this.lits[indLit] = this.lits[indLit] ^ 1;
                 this.degree++;
             }
             this.moreThan = true;
         }
     }
 
     /**
      * propagates the value of a falsified literal
      * 
      * @param s
      *            tool for literal propagation
      * @param p
      *            falsified literal
      * @return false if an inconistency is detected, else true
      */
     public boolean propagate(UnitPropagationListener s, int p) {
 
         // Si la contrainte est responsable de propagation unitaire
         if (this.watchCumul == this.degree) {
             this.voc.watch(p, this);
             return false;
         }
 
         // Recherche du litt?ral falsifi?
         int indFalsified = 0;
         while ((this.lits[indFalsified] ^ 1) != p) {
             indFalsified++;
         }
         assert this.watchCumul > this.degree;
 
         // Recherche du litt?ral swap
         int indSwap = this.degree + 1;
         while (indSwap < this.lits.length
                 && this.voc.isFalsified(this.lits[indSwap])) {
             indSwap++;
         }
 
         // Mise ? jour de la contrainte
         if (indSwap == this.lits.length) {
             // Si aucun litt?ral n'a ?t? trouv?
             this.voc.watch(p, this);
             // La limite est atteinte
             this.watchCumul--;
             assert this.watchCumul == this.degree;
             this.voc.undos(p).push(this);
 
             // On met en queue les litt?raux impliqu?s
             for (int i = 0; i <= this.degree; i++) {
                 if (p != (this.lits[i] ^ 1) && !s.enqueue(this.lits[i], this)) {
                     return false;
                 }
             }
 
             return true;
         }
         // Si un litt?ral a ?t? trouv? on les ?change
         int tmpInt = this.lits[indSwap];
         this.lits[indSwap] = this.lits[indFalsified];
         this.lits[indFalsified] = tmpInt;
 
         // On observe le nouveau litt?ral
         this.voc.watch(tmpInt ^ 1, this);
 
         return true;
     }
 
     /**
      * Removes a constraint from the solver
      * 
      * @since 2.1
      */
     public void remove(UnitPropagationListener upl) {
         for (int i = 0; i < Math.min(this.degree + 1, this.lits.length); i++) {
             this.voc.watches(this.lits[i] ^ 1).remove(this);
         }
     }
 
     /**
      * Rescales the activity value of the constraint
      * 
      * @param d
      *            rescale factor
      */
     public void rescaleBy(double d) {
         // TODO rescaleBy
     }
 
     /**
      * simplifies the constraint
      * 
      * @return true if the constraint is satisfied, else false
      */
     public boolean simplify() {
         // Calcul de la valeur actuelle
         for (int i = 0, count = 0; i < this.lits.length; i++) {
             if (this.voc.isSatisfied(this.lits[i]) && ++count == this.degree) {
                 return true;
             }
         }
 
         return false;
     }
 
     /**
      * Returns a string representation of the constraint.
      * 
      * @return representation of the constraint.
      */
     @Override
     public String toString() {
         StringBuffer stb = new StringBuffer();
         stb.append("Card (" + this.lits.length + ") : ");
         if (this.lits.length > 0) {
             // if (voc.isUnassigned(lits[0])) {
             stb.append(Lits.toString(this.lits[0]));
             stb.append("[");
             stb.append(this.voc.valueToString(this.lits[0]));
             stb.append("@");
             stb.append(this.voc.getLevel(this.lits[0]));
             stb.append("]");
             stb.append(" "); //$NON-NLS-1$
             // }
             for (int i = 1; i < this.lits.length; i++) {
                 // if (voc.isUnassigned(lits[i])) {
                 stb.append(" + "); //$NON-NLS-1$
                 stb.append(Lits.toString(this.lits[i]));
                 stb.append("[");
                 stb.append(this.voc.valueToString(this.lits[i]));
                 stb.append("@");
                 stb.append(this.voc.getLevel(this.lits[i]));
                 stb.append("]");
                 stb.append(" "); //$NON-NLS-1$
                 // }
             }
             stb.append(">= "); //$NON-NLS-1$
             stb.append(this.degree);
         }
         return stb.toString();
     }
 
     /**
      * Updates information on the constraint in case of a backtrack
      * 
      * @param p
      *            unassigned literal
      */
     public void undo(int p) {
         // Le litt?ral observ? et falsifi? devient non assign?
         this.watchCumul++;
     }
 
     public void setLearnt() {
         throw new UnsupportedOperationException();
     }
 
     public void register() {
         throw new UnsupportedOperationException();
     }
 
     public int size() {
         return this.lits.length;
     }
 
     public int get(int i) {
         return this.lits[i];
     }
 
     public void assertConstraint(UnitPropagationListener s) {
         throw new UnsupportedOperationException();
     }
 
     protected void computeWatches() {
         int indSwap = this.lits.length;
         int tmpInt;
         for (int i = 0; i <= this.degree && i < indSwap; i++) {
             while (this.voc.isFalsified(this.lits[i]) && --indSwap > i) {
                 tmpInt = this.lits[i];
                 this.lits[i] = this.lits[indSwap];
                 this.lits[indSwap] = tmpInt;
             }
 
             // Si le litteral est observable
             if (!this.voc.isFalsified(this.lits[i])) {
                 this.watchCumul++;
                 this.voc.watch(this.lits[i] ^ 1, this);
             }
         }
         if (learnt()) {
             // chercher tous les litteraux a regarder
             // par ordre de niveau decroissant
             int free = 1;
             while (this.watchCumul <= this.degree && free > 0) {
                 free = 0;
                 // regarder le litteral falsifie au plus bas niveau
                 int maxlevel = -1, maxi = -1;
                 for (int i = this.watchCumul; i < this.lits.length; i++) {
                     if (this.voc.isFalsified(this.lits[i])) {
                         free++;
                         int level = this.voc.getLevel(this.lits[i]);
                         if (level > maxlevel) {
                             maxi = i;
                             maxlevel = level;
                         }
                     }
                 }
                 if (free > 0) {
                     assert maxi >= 0;
                     this.voc.watch(this.lits[maxi] ^ 1, this);
                     tmpInt = this.lits[maxi];
                     this.lits[maxi] = this.lits[this.watchCumul];
                     this.lits[this.watchCumul] = tmpInt;
                     this.watchCumul++;
                     free--;
                     assert free >= 0;
                 }
             }
             assert this.lits.length == 1 || this.watchCumul > 1;
         }
 
     }
 
     protected MinWatchCard computePropagation(UnitPropagationListener s)
             throws ContradictionException {
 
         // Si on a des litteraux impliques
         if (this.watchCumul == this.degree) {
             for (int i = 0; i < this.lits.length; i++) {
                 if (!s.enqueue(this.lits[i])) {
                     throw new ContradictionException();
                 }
             }
             return null;
         }
 
         // Si on n'observe pas suffisamment
         if (this.watchCumul < this.degree) {
             throw new ContradictionException();
         }
         return this;
     }
 
     public int[] getLits() {
         int[] tmp = new int[size()];
         System.arraycopy(this.lits, 0, tmp, 0, size());
         return tmp;
     }
 
     public ILits getVocabulary() {
         return this.voc;
     }
 
     @Override
     public boolean equals(Object card) {
         if (card == null) {
             return false;
         }
         try {
             MinWatchCard mcard = (MinWatchCard) card;
             if (mcard.degree != this.degree) {
                 return false;
             }
             if (this.lits.length != mcard.lits.length) {
                 return false;
             }
             boolean ok;
             for (int lit : this.lits) {
                 ok = false;
                 for (int lit2 : mcard.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;
         }
         sum += this.degree;
         return (int) sum / (this.lits.length + 1);
     }
 
     /**
      * @since 2.1
      */
     public void forwardActivity(double claInc) {
         // do nothing
     }
 
     public boolean canBePropagatedMultipleTimes() {
         return true;
     }
 
     public Constr toConstraint() {
         return this;
     }
 
     public void calcReasonOnTheFly(int p, IVecInt trail, IVecInt outReason) {
         throw new UnsupportedOperationException("Not implemented yet!");
     }
 }