/*******************************************************************************
    * 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;
  
  import java.math.BigInteger;
  
  import org.sat4j.core.VecInt;
  import org.sat4j.specs.ContradictionException;
  import org.sat4j.specs.IConstr;
  import org.sat4j.specs.IOptimizationProblem;
  import org.sat4j.specs.IVecInt;
  import org.sat4j.specs.TimeoutException;
  
  /**
   * A decorator that computes minimal pseudo boolean models.
   * 
   * @author daniel
   * 
   */
  public class PseudoOptDecorator extends PBSolverDecorator implements
  		IOptimizationProblem {
  
  	/**
       * 
       */
  	private static final long serialVersionUID = 1L;
  
  	private ObjectiveFunction objfct;
  
  	private BigInteger objectiveValue;
  
  	private int[] prevmodel;
  	private boolean[] prevfullmodel;
  
  	private IConstr previousPBConstr;
  
  	public PseudoOptDecorator(IPBSolver solver) {
  		super(solver);
  	}
  
  	@Override
  	public boolean isSatisfiable() throws TimeoutException {
  		return isSatisfiable(VecInt.EMPTY);
  	}
  
  	@Override
  	public boolean isSatisfiable(boolean global) throws TimeoutException {
  		return isSatisfiable(VecInt.EMPTY, global);
  	}
  
  	@Override
  	public boolean isSatisfiable(IVecInt assumps, boolean global)
  			throws TimeoutException {
  		boolean result = super.isSatisfiable(assumps, true);
  		if (result) {
  			prevmodel = super.model();
  			prevfullmodel = new boolean[nVars()];
  			for (int i = 0; i < nVars(); i++) {
  				prevfullmodel[i] = decorated().model(i + 1);
  			}
  		} else {
  			if (previousPBConstr != null) {
  				decorated().removeConstr(previousPBConstr);
  				previousPBConstr = null;
  			}
  		}
  		return result;
  	}
  
  	@Override
  	public boolean isSatisfiable(IVecInt assumps) throws TimeoutException {
  		return isSatisfiable(assumps, true);
  	}
  
 	@Override
 	public void setObjectiveFunction(ObjectiveFunction objf) {
 		objfct = objf;
 		decorated().setObjectiveFunction(objf);
 	}
 
 	public boolean admitABetterSolution() throws TimeoutException {
 		return admitABetterSolution(VecInt.EMPTY);
 	}
 
 	public boolean admitABetterSolution(IVecInt assumps)
 			throws TimeoutException {
 		try {
 			boolean result = super.isSatisfiable(assumps, true);
 			if (result) {
 				prevmodel = super.model();
 				prevfullmodel = new boolean[nVars()];
 				for (int i = 0; i < nVars(); i++) {
 					prevfullmodel[i] = decorated().model(i + 1);
 				}
 				if (objfct != null) {
 					calculateObjective();
 				}
 			} else {
 				if (previousPBConstr != null) {
 					decorated().removeConstr(previousPBConstr);
 					previousPBConstr = null;
 				}
 			}
 			return result;
 		} catch (TimeoutException te) {
 			if (previousPBConstr != null) {
 				decorated().removeConstr(previousPBConstr);
 				previousPBConstr = null;
 			}
 			throw te;
 		}
 	}
 
 	public boolean hasNoObjectiveFunction() {
 		return objfct == null;
 	}
 
 	public boolean nonOptimalMeansSatisfiable() {
 		return true;
 	}
 
 	public Number calculateObjective() {
 		if (objfct == null) {
 			throw new UnsupportedOperationException(
 					"The problem does not contain an objective function");
 		}
 		objectiveValue = objfct.calculateDegree(prevmodel);
 		return objectiveValue;
 	}
 
 	public void discardCurrentSolution() throws ContradictionException {
 		if (previousPBConstr != null) {
 			super.removeSubsumedConstr(previousPBConstr);
 		}
 		if (objfct != null && objectiveValue != null) {
 			previousPBConstr = super.addPseudoBoolean(objfct.getVars(), objfct
 					.getCoeffs(), false, objectiveValue
 					.subtract(BigInteger.ONE));
 		}
 	}
 
 	@Override
 	public void reset() {
 		previousPBConstr = null;
 		super.reset();
 	}
 
 	@Override
 	public int[] model() {
 		// DLB findbugs ok
 		return prevmodel;
 	}
 
 	@Override
 	public boolean model(int var) {
 		return prevfullmodel[var - 1];
 	}
 
 	@Override
 	public String toString(String prefix) {
 		return prefix + "Pseudo Boolean Optimization\n"
 				+ super.toString(prefix);
 	}
 
 	public Number getObjectiveValue() {
 		return objectiveValue;
 	}
 
 	public void discard() throws ContradictionException {
 		discardCurrentSolution();
 	}
 
 	public void forceObjectiveValueTo(Number forcedValue)
 			throws ContradictionException {
 		super.addPseudoBoolean(objfct.getVars(), objfct.getCoeffs(), false,
 				(BigInteger) forcedValue);
 	}
 }