/*******************************************************************************
    * SAT4J: a SATisfiability library for Java Copyright (C) 2004, 2012 Artois University and CNRS
    *
    * 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++.
   *
   * Contributors:
   *   CRIL - initial API and implementation
   *******************************************************************************/
  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;
  
      private boolean isSolutionOptimal;
  
      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) {
         this.costs = new int[howmany + 1];
         // Arrays.fill(costs, 1);
         this.vars.clear();
         this.coeffs.clear();
         for (int i = 1; i <= howmany; i++) {
             this.vars.push(i);
             this.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 this.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) {
         this.costs[var] = cost;
         this.coeffs.set(var - 1, BigInteger.valueOf(cost));
     }
 
     public boolean admitABetterSolution() throws TimeoutException {
         return admitABetterSolution(VecInt.EMPTY);
     }
 
     public boolean admitABetterSolution(IVecInt assumps)
             throws TimeoutException {
         this.isSolutionOptimal = false;
         boolean result = super.isSatisfiable(assumps, true);
         if (result) {
             this.prevmodel = super.model();
             calculateObjective();
         } else {
             this.isSolutionOptimal = true;
         }
         return result;
     }
 
     public boolean hasNoObjectiveFunction() {
         return false;
     }
 
     public boolean nonOptimalMeansSatisfiable() {
         return true;
     }
 
     public Number calculateObjective() {
         this.objectivevalue = calculateDegree(this.prevmodel);
         return this.objectivevalue;
     }
 
     private int calculateDegree(int[] prevmodel2) {
         int tmpcost = 0;
         for (int i = 1; i < this.costs.length; i++) {
             if (prevmodel2[i - 1] > 0) {
                 tmpcost += this.costs[i];
             }
         }
         return tmpcost;
     }
 
     public void discardCurrentSolution() throws ContradictionException {
         if (this.prevConstr != null) {
             super.removeSubsumedConstr(this.prevConstr);
         }
         try {
             this.prevConstr = super.addPseudoBoolean(this.vars, this.coeffs,
                     false, BigInteger.valueOf(this.objectivevalue - 1));
         } catch (ContradictionException e) {
             this.isSolutionOptimal = true;
             throw e;
         }
     }
 
     @Override
     public void reset() {
         this.prevConstr = null;
         super.reset();
     }
 
     @Override
     public int[] model() {
         // DLB findbugs ok
         return this.prevmodel;
     }
 
     public Number getObjectiveValue() {
         return this.objectivevalue;
     }
 
     public void discard() throws ContradictionException {
         discardCurrentSolution();
     }
 
     public void forceObjectiveValueTo(Number forcedValue)
             throws ContradictionException {
         super.addPseudoBoolean(this.vars, this.coeffs, false,
                 (BigInteger) forcedValue);
     }
 
     public boolean isOptimal() {
         return this.isSolutionOptimal;
     }
 
     public void setTimeoutForFindingBetterSolution(int seconds) {
         // TODO
         throw new UnsupportedOperationException("No implemented yet");
     }
 }