/*******************************************************************************
    * 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.tools.xplain;
  
  import java.util.Arrays;
  import java.util.Collection;
  import java.util.HashMap;
  import java.util.HashSet;
  import java.util.Map;
  
  import org.sat4j.core.VecInt;
  import org.sat4j.specs.ContradictionException;
  import org.sat4j.specs.IConstr;
  import org.sat4j.specs.ISolver;
  import org.sat4j.specs.IVecInt;
  import org.sat4j.specs.IteratorInt;
  import org.sat4j.specs.TimeoutException;
  import org.sat4j.tools.SolverDecorator;
  
  /**
   * Computation of MUS in a structured CNF, i.e. the clauses belong to
   * components, the explanation is to be extracted in terms of components.
   * 
   * @author daniel
   * 
   * @param <T>
   *            a subinterface to ISolver.
   * @since 2.1
   */
  public class HighLevelXplain<T extends ISolver> extends SolverDecorator<T>
          implements Explainer {
  
      protected Map<Integer, Integer> constrs = new HashMap<Integer, Integer>();
  
      protected IVecInt assump;
  
      private int lastCreatedVar;
      private boolean pooledVarId = false;
  
      private MinimizationStrategy xplainStrategy = new DeletionStrategy();
      private final Map<Integer, Integer> highLevelToVar = new HashMap<Integer, Integer>();
  
      public HighLevelXplain(T solver) {
          super(solver);
      }
  
      /**
       * 
       * @param literals
       *            a clause
       * @param desc
       *            the level of the clause set
       * @return on object representing that clause in the solver.
       * @throws ContradictionException
       */
      public IConstr addClause(IVecInt literals, int desc)
              throws ContradictionException {
          if (desc == 0) {
              return addClause(literals);
          }
          Integer hlvar = this.highLevelToVar.get(desc);
          if (hlvar == null) {
              hlvar = createNewVar(literals);
              this.highLevelToVar.put(desc, hlvar);
              this.constrs.put(hlvar, desc);
          }
          literals.push(hlvar);
          IConstr constr = super.addClause(literals);
          return constr;
      }
  
      /**
      * 
      * @param literals
      * @return
      * @since 2.1
      */
     protected int createNewVar(IVecInt literals) {
         if (this.pooledVarId) {
             this.pooledVarId = false;
             return this.lastCreatedVar;
         }
         this.lastCreatedVar = nextFreeVarId(true);
         return this.lastCreatedVar;
     }
 
     protected void discardLastestVar() {
         this.pooledVarId = true;
     }
 
     @Override
     public IConstr addAtLeast(IVecInt literals, int degree)
             throws ContradictionException {
         throw new UnsupportedOperationException();
     }
 
     @Override
     public IConstr addAtMost(IVecInt literals, int degree)
             throws ContradictionException {
         throw new UnsupportedOperationException();
     }
 
     /**
 	 * 
 	 */
     private static final long serialVersionUID = 1L;
 
     /**
      * @since 2.2.4
      * @return
      * @throws TimeoutException
      */
     private IVecInt explanationKeys() throws TimeoutException {
         assert !isSatisfiable(this.assump);
         ISolver solver = decorated();
         if (solver instanceof SolverDecorator<?>) {
             solver = ((SolverDecorator<? extends ISolver>) solver).decorated();
         }
         return this.xplainStrategy.explain(solver, this.constrs, this.assump);
     }
 
     public int[] minimalExplanation() throws TimeoutException {
         Collection<Integer> components = explain();
         int[] model = new int[components.size()];
         int i = 0;
         for (int c : components) {
             model[i++] = c;
         }
         Arrays.sort(model);
         return model;
     }
 
     /**
      * @since 2.1
      * @return
      * @throws TimeoutException
      */
     public Collection<Integer> explain() throws TimeoutException {
         IVecInt keys = explanationKeys();
         Collection<Integer> explanation = new HashSet<Integer>(keys.size());
         for (IteratorInt it = keys.iterator(); it.hasNext();) {
             explanation.add(this.constrs.get(it.next()));
         }
         return explanation;
     }
 
     /**
      * @since 2.1
      */
     public void cancelExplanation() {
         this.xplainStrategy.cancelExplanationComputation();
     }
 
     @Override
     public int[] findModel() throws TimeoutException {
         this.assump = VecInt.EMPTY;
         IVecInt extraVariables = new VecInt();
         for (Integer p : this.constrs.keySet()) {
             extraVariables.push(-p);
         }
         return super.findModel(extraVariables);
     }
 
     @Override
     public int[] findModel(IVecInt assumps) throws TimeoutException {
         this.assump = assumps;
         IVecInt extraVariables = new VecInt();
         assumps.copyTo(extraVariables);
         for (Integer p : this.constrs.keySet()) {
             extraVariables.push(-p);
         }
         return super.findModel(extraVariables);
     }
 
     @Override
     public boolean isSatisfiable() throws TimeoutException {
         this.assump = VecInt.EMPTY;
         IVecInt extraVariables = new VecInt();
         for (Integer p : this.constrs.keySet()) {
             extraVariables.push(-p);
         }
         return super.isSatisfiable(extraVariables);
     }
 
     @Override
     public boolean isSatisfiable(boolean global) throws TimeoutException {
         this.assump = VecInt.EMPTY;
         IVecInt extraVariables = new VecInt();
         for (Integer p : this.constrs.keySet()) {
             extraVariables.push(-p);
         }
         return super.isSatisfiable(extraVariables, global);
     }
 
     @Override
     public boolean isSatisfiable(IVecInt assumps) throws TimeoutException {
         this.assump = assumps;
         IVecInt extraVariables = new VecInt();
         assumps.copyTo(extraVariables);
         for (Integer p : this.constrs.keySet()) {
             extraVariables.push(-p);
         }
         return super.isSatisfiable(extraVariables);
     }
 
     @Override
     public boolean isSatisfiable(IVecInt assumps, boolean global)
             throws TimeoutException {
         this.assump = assumps;
         IVecInt extraVariables = new VecInt();
         assumps.copyTo(extraVariables);
         for (Integer p : this.constrs.keySet()) {
             extraVariables.push(-p);
         }
         return super.isSatisfiable(extraVariables, global);
     }
 
     @Override
     public int[] model() {
         int[] fullmodel = super.model();
         if (fullmodel == null) {
             return null;
         }
         int[] model = new int[fullmodel.length - this.constrs.size()];
         int j = 0;
         for (int element : fullmodel) {
             if (this.constrs.get(Math.abs(element)) == null) {
                 model[j++] = element;
             }
         }
         return model;
     }
 
     @Override
     public String toString(String prefix) {
         System.out.println(prefix
                 + "High Level Explanation (MUS) enabled solver");
         System.out.println(prefix + this.xplainStrategy);
         return super.toString(prefix);
     }
 
     public void setMinimizationStrategy(MinimizationStrategy strategy) {
         this.xplainStrategy = strategy;
     }
 
 }