/*******************************************************************************
    * 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
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   * may use your version of this file under the terms of the EPL or the LGPL.
   *******************************************************************************/
  package org.sat4j.maxsat;
  
  import java.math.BigInteger;
  
  import org.sat4j.core.Vec;
  import org.sat4j.core.VecInt;
  import org.sat4j.pb.IPBSolver;
  import org.sat4j.pb.PBSolverDecorator;
  import org.sat4j.specs.ContradictionException;
  import org.sat4j.specs.IConstr;
  import org.sat4j.specs.IOptimizationProblem;
  import org.sat4j.specs.IVec;
  import org.sat4j.specs.IVecInt;
  import org.sat4j.specs.TimeoutException;
  
  /**
   * A decorator that computes minimal cost models. That problem is also known as
   * binate covering problem.
   * 
   * Please make sure that newVar(howmany) is called first to setup the decorator.
   * 
   * @author daniel
   * 
   */
  public class MinCostDecorator extends PBSolverDecorator implements
  		IOptimizationProblem {
  
  	/**
       * 
       */
  	private static final long serialVersionUID = 1L;
  
  	private int[] costs;
  
  	private int[] prevmodel;
  
  	private final IVecInt vars = new VecInt();
  
  	private final IVec<BigInteger> coeffs = new Vec<BigInteger>();
  
  	private int objectivevalue;
  
  	private IConstr prevConstr;
  
  	public MinCostDecorator(IPBSolver solver) {
  		super(solver);
  	}
  
  	/*
  	 * (non-Javadoc)
  	 * 
  	 * @see org.sat4j.tools.SolverDecorator#newVar()
  	 */
  	@Override
  	public int newVar() {
  		throw new UnsupportedOperationException();
  	}
  
  	/**
  	 * Setup the number of variables to use inside the solver.
  	 * 
  	 * It is mandatory to call that method before setting the cost of the
  	 * variables.
  	 * 
  	 * @param howmany
  	 *            the maximum number of variables in the solver.
  	 */
  	@Override
  	public int newVar(int howmany) {
  		costs = new int[howmany + 1];
  		// Arrays.fill(costs, 1);
  		vars.clear();
  		coeffs.clear();
  		for (int i = 1; i <= howmany; i++) {
  			vars.push(i);
  			coeffs.push(BigInteger.ZERO);
  		}
  		// should the default cost be 1????
  		// here it is 0
  		return super.newVar(howmany);
  	}
 
 	/**
 	 * to know the cost of a given var.
 	 * 
 	 * @param var
 	 *            a variable in dimacs format
 	 * @return the cost of that variable when assigned to true
 	 */
 	public int costOf(int var) {
 		return costs[var];
 	}
 
 	/**
 	 * to set the cost of a given var.
 	 * 
 	 * @param var
 	 *            a variable in dimacs format
 	 * @param cost
 	 *            the cost of var when assigned to true
 	 */
 	public void setCost(int var, int cost) {
 		costs[var] = cost;
 		coeffs.set(var - 1, BigInteger.valueOf(cost));
 	}
 
 	public boolean admitABetterSolution() throws TimeoutException {
 		return admitABetterSolution(VecInt.EMPTY);
 	}
 
 	public boolean admitABetterSolution(IVecInt assumps)
 			throws TimeoutException {
 		boolean result = super.isSatisfiable(assumps, true);
 		if (result) {
 			prevmodel = super.model();
 			calculateObjective();
 		}
 		return result;
 	}
 
 	public boolean hasNoObjectiveFunction() {
 		return false;
 	}
 
 	public boolean nonOptimalMeansSatisfiable() {
 		return true;
 	}
 
 	public Number calculateObjective() {
 		objectivevalue = calculateDegree(prevmodel);
 		return new Integer(objectivevalue);
 	}
 
 	private int calculateDegree(int[] prevmodel2) {
 		int tmpcost = 0;
 		for (int i = 1; i < costs.length; i++) {
 			if (prevmodel2[i - 1] > 0) {
 				tmpcost += costs[i];
 			}
 		}
 		return tmpcost;
 	}
 
 	public void discardCurrentSolution() throws ContradictionException {
 		if (prevConstr!=null) {
 			super.removeSubsumedConstr(prevConstr);
 		}
 		prevConstr = super.addPseudoBoolean(vars, coeffs, false, BigInteger
 				.valueOf(objectivevalue - 1));
 	}
 
 	@Override
 	public void reset() {
 		prevConstr = null;
 		super.reset();
 	}
 
 	@Override
 	public int[] model() {
 		// DLB findbugs ok
 		return prevmodel;
 	}
 
 	public Number getObjectiveValue() {
 		return objectivevalue;
 	}
 
 	public void discard() throws ContradictionException {
 		discardCurrentSolution();
 	}
 
 	public void forceObjectiveValueTo(Number forcedValue)
 			throws ContradictionException {
 		super.addPseudoBoolean(vars, coeffs, false, (BigInteger)
 				forcedValue);
 	}
 }