/*******************************************************************************
    * 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.orders;
  
  import java.io.PrintWriter;
  import java.io.Serializable;
  import java.util.Random;
  
  import org.sat4j.minisat.core.ILits;
  import org.sat4j.minisat.core.IOrder;
  import org.sat4j.minisat.core.IPhaseSelectionStrategy;
  
  /**
   * @since 2.2
   */
  public class RandomWalkDecorator implements IOrder, Serializable {
  
      /**
       * 
       */
      private static final long serialVersionUID = 1L;
  
      private final VarOrderHeap decorated;
  
      private double p;
  
      private static final Random RAND = new Random(123456789);
      private ILits voc;
      private int nbRandomWalks;
  
      public RandomWalkDecorator(VarOrderHeap order) {
          this(order, 0.01);
      }
  
      public RandomWalkDecorator(VarOrderHeap order, double p) {
          this.decorated = order;
          this.p = p;
      }
  
      public void assignLiteral(int q) {
          this.decorated.assignLiteral(q);
      }
  
      public IPhaseSelectionStrategy getPhaseSelectionStrategy() {
          return this.decorated.getPhaseSelectionStrategy();
      }
  
      public double getProbability() {
          return this.p;
      }
  
      public void setProbability(double p) {
          this.p = p;
      }
  
      public void init() {
          this.decorated.init();
      }
  
      public void printStat(PrintWriter out, String prefix) {
          out.println(prefix + "random walks\t: " + this.nbRandomWalks);
          this.decorated.printStat(out, prefix);
      }
  
      public int select() {
          if (RAND.nextDouble() < this.p) {
              int var, lit, max;
  
              while (!this.decorated.heap.empty()) {
                  max = this.decorated.heap.size();
                  var = this.decorated.heap.get(RAND.nextInt(max) + 1);
                  lit = getPhaseSelectionStrategy().select(var);
                 if (this.voc.isUnassigned(lit)) {
                     this.nbRandomWalks++;
                     return lit;
                 }
             }
         }
         return this.decorated.select();
     }
 
     public void setLits(ILits lits) {
         this.decorated.setLits(lits);
         this.voc = lits;
         this.nbRandomWalks = 0;
     }
 
     public void setPhaseSelectionStrategy(IPhaseSelectionStrategy strategy) {
         this.decorated.setPhaseSelectionStrategy(strategy);
     }
 
     public void setVarDecay(double d) {
         this.decorated.setVarDecay(d);
     }
 
     public void undo(int x) {
         this.decorated.undo(x);
     }
 
     public void updateVar(int q) {
         this.decorated.updateVar(q);
     }
 
     public double varActivity(int q) {
         return this.decorated.varActivity(q);
     }
 
     public void varDecayActivity() {
         this.decorated.varDecayActivity();
     }
 
     public void updateVarAtDecisionLevel(int q) {
         this.decorated.updateVarAtDecisionLevel(q);
     }
 
     @Override
     public String toString() {
         return this.decorated.toString() + " with random walks " + this.p;
     }
 
     public double[] getVariableHeuristics() {
         return this.decorated.getVariableHeuristics();
     }
 
 }