/*******************************************************************************
    * 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 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++.
   * 
   *******************************************************************************/
  package org.sat4j.opt;
  
  import org.sat4j.core.VecInt;
  import org.sat4j.specs.ContradictionException;
  import org.sat4j.specs.IConstr;
  import org.sat4j.specs.IOptimizationProblem;
  import org.sat4j.specs.ISolver;
  import org.sat4j.specs.IVecInt;
  import org.sat4j.specs.TimeoutException;
  import org.sat4j.tools.SolverDecorator;
  
  /**
   * Computes a solution with the smallest number of satisfied literals.
   * 
   * Please make sure that newVar(howmany) is called first to setup the decorator.
   * 
   * @author leberre
   */
  public final class MinOneDecorator extends SolverDecorator<ISolver> implements
  		IOptimizationProblem {
  
  	/**
       * 
       */
  	private static final long serialVersionUID = 1L;
  
  	private int[] prevmodel;
  
  	private boolean isSolutionOptimal;
  
  	public MinOneDecorator(ISolver solver) {
  		super(solver);
  	}
  
  	public boolean admitABetterSolution() throws TimeoutException {
  		return admitABetterSolution(VecInt.EMPTY);
  	}
  
  	/**
  	 * @since 2.1
  	 */
  	public boolean admitABetterSolution(IVecInt assumps)
  			throws TimeoutException {
  		isSolutionOptimal = false;
  		boolean result = isSatisfiable(assumps, true);
  		if (result) {
  			prevmodel = super.model();
  			calculateObjectiveValue();
  		} else {
  			isSolutionOptimal = true;
  		}
  		return result;
  	}
  
  	public boolean hasNoObjectiveFunction() {
  		return false;
  	}
  
  	public boolean nonOptimalMeansSatisfiable() {
  		return true;
  	}
  
  	private int counter;
  
  	public Number calculateObjective() {
  		calculateObjectiveValue();
  		return counter;
  	}
  
  	private void calculateObjectiveValue() {
  		counter = 0;
  		for (int p : prevmodel) {
 			if (p > 0) {
 				counter++;
 			}
 		}
 	}
 
 	private final IVecInt literals = new VecInt();
 
 	private IConstr previousConstr;
 
 	/**
 	 * @since 2.1
 	 */
 	public void discardCurrentSolution() throws ContradictionException {
 		if (literals.isEmpty()) {
 			for (int i = 1; i <= nVars(); i++) {
 				literals.push(i);
 			}
 		}
 		if (previousConstr != null) {
 			super.removeConstr(previousConstr);
 		}
 		previousConstr = addAtMost(literals, counter - 1);
 	}
 
 	@Override
 	public int[] model() {
 		// DLB findbugs ok
 		return prevmodel;
 	}
 
 	@Override
 	public void reset() {
 		literals.clear();
 		previousConstr = null;
 		super.reset();
 	}
 
 	/**
 	 * @since 2.1
 	 */
 	public Number getObjectiveValue() {
 		return counter;
 	}
 
 	public void discard() throws ContradictionException {
 		discardCurrentSolution();
 	}
 
 	/**
 	 * @since 2.1
 	 */
 	public void forceObjectiveValueTo(Number forcedValue)
 			throws ContradictionException {
 		try {
 			addAtMost(literals, forcedValue.intValue());
 		} catch (ContradictionException ce) {
 			isSolutionOptimal = true;
 			throw ce;
 		}
 
 	}
 
 	public boolean isOptimal() {
 		return isSolutionOptimal;
 	}
 }