/*******************************************************************************
    * 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 org.sat4j.core.VecInt;
  import org.sat4j.specs.ContradictionException;
  import org.sat4j.specs.IOptimizationProblem;
  import org.sat4j.specs.IVecInt;
  import org.sat4j.specs.TimeoutException;
  
  /**
   * Utility class to use optimization solvers instead of simple SAT solvers in
   * code meant for SAT solvers.
   * 
   * @author daniel
   */
  public class OptToPBSATAdapter extends PBSolverDecorator {
  
  	/**
       * 
       */
  	private static final long serialVersionUID = 1L;
  
  	IOptimizationProblem problem;
  
  	boolean modelComputed = false;
  
  	private final IVecInt assumps = new VecInt();
  
  	private long begin;
  
  	public OptToPBSATAdapter(IOptimizationProblem problem) {
  		super((IPBSolver) problem);
  		this.problem = problem;
  	}
  
  	@Override
  	public boolean isSatisfiable() throws TimeoutException {
  		modelComputed = false;
  		assumps.clear();
  		begin = System.currentTimeMillis();
  		if (problem.hasNoObjectiveFunction()) {
  			return modelComputed = problem.isSatisfiable();
  		}
  		return problem.admitABetterSolution();
  	}
  
  	@Override
  	public boolean isSatisfiable(boolean global) throws TimeoutException {
  		return isSatisfiable();
  	}
  
  	@Override
  	public boolean isSatisfiable(IVecInt myAssumps, boolean global)
  			throws TimeoutException {
  		return isSatisfiable(myAssumps);
  	}
  
  	@Override
  	public boolean isSatisfiable(IVecInt myAssumps) throws TimeoutException {
  		modelComputed = false;
  		this.assumps.clear();
  		myAssumps.copyTo(this.assumps);
  		begin = System.currentTimeMillis();
  		if (problem.hasNoObjectiveFunction()) {
  			return modelComputed = problem.isSatisfiable(myAssumps);
  		}
  		return problem.admitABetterSolution(myAssumps);
  	}
  
  	@Override
  	public int[] model() {
  		if (modelComputed)
  			return problem.model();
 		try {
 			assert problem.admitABetterSolution(assumps);
 			assert !problem.hasNoObjectiveFunction();
 			do {
 				problem.discardCurrentSolution();
 				if (isVerbose()) {
 					System.out.println(getLogPrefix()
 							+ "Current objective function value: "
 							+ problem.getObjectiveValue() + "("
 							+ ((System.currentTimeMillis() - begin) / 1000.0)
 							+ "s)");
 				}
 			} while (problem.admitABetterSolution(assumps));
 		} catch (TimeoutException e) {
 			if (isVerbose()) {
 				System.out.println(getLogPrefix() + "Solver timed out after "
 						+ ((System.currentTimeMillis() - begin) / 1000.0)
 						+ "s)");
 			}
 		} catch (ContradictionException e) {
 			// OK, optimal model found
 		}
 		modelComputed = true;
 		return problem.model();
 	}
 
 	@Override
 	public boolean model(int var) {
 		if (!modelComputed)
 			model();
 		return problem.model(var);
 	}
 
 	@Override
 	public String toString(String prefix) {
 		return prefix + "Optimization to Pseudo Boolean adapter\n"
 				+ super.toString(prefix);
 	}
 
 	public boolean isOptimal() {
 		return problem.isOptimal();
 	}
 }