/*******************************************************************************
   * SAT4J: a SATisfiability library for Java Copyright (C) 2004-2008 Daniel Le Berre
   *
   * 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 pseudo boolean algorithms described in:
  * A fast pseudo-Boolean constraint solver Chai, D.; Kuehlmann, A.
  * Computer-Aided Design of Integrated Circuits and Systems, IEEE Transactions on
  * Volume 24, Issue 3, March 2005 Page(s): 305 - 317
  * 
  * and 
  * Heidi E. Dixon, 2004. Automating Pseudo-Boolean Inference within a DPLL 
  * Framework. Ph.D. Dissertation, University of Oregon.
  *******************************************************************************/
  package org.sat4j.pb.core;
  
  import org.sat4j.core.Vec;
  import org.sat4j.minisat.constraints.cnf.Lits;
  import org.sat4j.minisat.core.AssertingClauseGenerator;
  import org.sat4j.minisat.core.Constr;
  import org.sat4j.minisat.core.ILits;
  import org.sat4j.minisat.core.IOrder;
  import org.sat4j.minisat.core.LearningStrategy;
  import org.sat4j.minisat.core.Pair;
  import org.sat4j.minisat.core.RestartStrategy;
  import org.sat4j.minisat.core.SearchParams;
  import org.sat4j.minisat.restarts.MiniSATRestarts;
  import org.sat4j.pb.constraints.pb.ConflictMap;
  import org.sat4j.pb.constraints.pb.IConflict;
  import org.sat4j.pb.constraints.pb.PBConstr;
  import org.sat4j.specs.IVec;
  
  /**
   * @author parrain To change the template for this generated type comment go to
   *         Window - Preferences - Java - Code Generation - Code and Comments
   */
  public class PBSolverCP<L extends ILits> extends PBSolver<L> {
  
      private static final long serialVersionUID = 1L;
      
      /**
       * @param acg
       * @param learner
       * @param dsf
       */
      public PBSolverCP(AssertingClauseGenerator acg, LearningStrategy<L,PBDataStructureFactory<L>> learner,
              PBDataStructureFactory<L> dsf, IOrder<L> order) {
          super(acg, learner, dsf, new SearchParams(1.5, 100), order,new MiniSATRestarts());
      }
  
      public PBSolverCP(AssertingClauseGenerator acg, LearningStrategy<L,PBDataStructureFactory<L>> learner, PBDataStructureFactory<L> dsf, SearchParams params, IOrder<L> order, RestartStrategy restarter) {
          super(acg, learner, dsf, params, order, restarter);
      }
  
      public PBSolverCP(AssertingClauseGenerator acg, LearningStrategy<L,PBDataStructureFactory<L>> learner, PBDataStructureFactory<L> dsf, SearchParams params, IOrder<L> order) {
          super(acg, learner, dsf, params, order,new MiniSATRestarts());
      }
  
       
      @Override
      public void analyze(Constr myconfl, Pair results) {
          int litImplied = trail.last();
          int currentLevel = voc.getLevel(litImplied);
          IConflict confl = chooseConflict((PBConstr)myconfl, currentLevel);
          initExplanation();
          buildExplanation(litImplied,myconfl);
          assert confl.slackConflict().signum() < 0;
          while (!confl.isAssertive(currentLevel)) {
              PBConstr constraint = (PBConstr)voc.getReason(litImplied);
              buildExplanation(litImplied,constraint);
              // result of the resolution is in the conflict (confl)
              confl.resolve(constraint, litImplied, this);
              assert confl.slackConflict().signum() <= 0;
              // implication trail is reduced
              if (trail.size() == 1)
                  break;
              undoOne();
              //assert decisionLevel() >= 0;
              if (decisionLevel() == 0)
              	break;
              litImplied = trail.last();
              if (voc.getLevel(litImplied) != currentLevel) {
                  trailLim.pop();
                  confl.updateSlack(voc.getLevel(litImplied));
              }
              assert voc.getLevel(litImplied) <= currentLevel;
             currentLevel = voc.getLevel(litImplied);
             assert confl.slackIsCorrect(currentLevel);
             assert currentLevel == decisionLevel();
             assert litImplied > 1;
         }
     	assert confl.isAssertive(currentLevel) || trail.size() == 1 || decisionLevel() == 0;
 
         assert currentLevel == decisionLevel();
         undoOne();
 
         // necessary informations to build a PB-constraint
         // are kept from the conflict
         if ((confl.size()==0) || ((decisionLevel() == 0 || trail.size() == 0) && confl.slackConflict().signum() < 0)){ 
         	results.reason = null;
         	results.backtrackLevel= -1;
         	return;
         }
         
         // assertive PB-constraint is build and referenced
         PBConstr resConstr = (PBConstr) dsfactory
               .createUnregisteredPseudoBooleanConstraint(confl);
         
         results.reason = resConstr;
         
         // the conflict give the highest decision level for the backtrack 
         // (which is less than current level) 
     	// assert confl.isAssertive(currentLevel);
         if (decisionLevel() == 0 || trail.size() == 0) 
         	results.backtrackLevel = -1;
         else
         	results.backtrackLevel =  confl.getBacktrackLevel(currentLevel);
     }
 
     @Override
     protected void analyzeAtRootLevel(Constr myconfl) {
         // first literal implied in the conflict
         int litImplied = trail.last();
         initExplanation();
         buildExplanation(litImplied,myconfl);
         while (!trail.isEmpty()) {
             PBConstr constraint = (PBConstr)voc.getReason(litImplied);
             if (constraint != null)
             	buildExplanation(litImplied,constraint);
             trail.pop();
             if (!trail.isEmpty())
             	litImplied = trail.last();
         }
     }
 
     IConflict chooseConflict(PBConstr myconfl, int level) {
         return ConflictMap.createConflict(myconfl, level);
     }
 
     @Override
     public String toString(String prefix) {
         return prefix + "Cutting planes based inference ("
                 + this.getClass().getName() + ")\n" + super.toString(prefix);
     }
     
     private IVec<String> conflictVariables = new Vec<String>();
     private IVec<String> conflictConstraints = new Vec<String>();
     
     void initExplanation(){
     	conflictVariables.clear();
     	conflictConstraints.clear();
     }
     
     void buildExplanation(int lit, Constr c){
     	if ((listOfVariables != null) && (listOfVariables.contains(lit>>1))){
     			conflictVariables.push(Lits.toString(lit));
     			conflictConstraints.push(c.toString());
     	}
     }
 
     @Override
 	public String getExplanation(){
     	if (!conflictVariables.isEmpty()){
     		assert conflictVariables.size() == conflictConstraints.size();
     		StringBuffer sb = new StringBuffer();
     		sb.append("Variables and constraints involved in unsatisfiability : \n");
     		for(int i = 0; i<conflictVariables.size();i++){
     			sb.append("Var : "+conflictVariables.get(i));
     			sb.append(" - Constr : "+conflictConstraints.get(i));
     			sb.append("\n");
     		}
     		return sb.toString();
     	}
     	return "";
     }
 }