/*******************************************************************************
    * 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.core.AssertingClauseGenerator;
  import org.sat4j.minisat.core.Constr;
  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 extends PBSolver {
  
  	private static final long serialVersionUID = 1L;
  
  	/**
  	 * @param acg
  	 * @param learner
  	 * @param dsf
  	 */
  	public PBSolverCP(AssertingClauseGenerator acg,
  			LearningStrategy<PBDataStructureFactory> learner,
  			PBDataStructureFactory dsf, IOrder order) {
  		super(acg, learner, dsf, new SearchParams(1.5, 100), order,
  				new MiniSATRestarts());
  	}
  
  	public PBSolverCP(AssertingClauseGenerator acg,
  			LearningStrategy<PBDataStructureFactory> learner,
  			PBDataStructureFactory dsf, SearchParams params, IOrder order,
  			RestartStrategy restarter) {
  		super(acg, learner, dsf, params, order, restarter);
  	}
  
  	public PBSolverCP(AssertingClauseGenerator acg,
  			LearningStrategy<PBDataStructureFactory> learner,
  			PBDataStructureFactory dsf, SearchParams params, IOrder 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);
  		assert confl.slackConflict().signum() < 0;
  		while (!confl.isAssertive(currentLevel)) {
  			PBConstr constraint = (PBConstr) voc.getReason(litImplied);
  			// 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);
 	}
 
 	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 final IVec<String> conflictVariables = new Vec<String>();
 	private final IVec<String> conflictConstraints = new Vec<String>();
 
 	void initExplanation() {
 		conflictVariables.clear();
 		conflictConstraints.clear();
 	}
 }