/*******************************************************************************
   * 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.
  *******************************************************************************/
  package org.sat4j.csp.constraints;
  
  import java.util.HashMap;
  import java.util.Map;
  
  import org.sat4j.csp.Domain;
  import org.sat4j.csp.Encoding;
  import org.sat4j.csp.Evaluable;
  import org.sat4j.csp.Var;
  import org.sat4j.specs.ContradictionException;
  import org.sat4j.specs.ISolver;
  import org.sat4j.specs.IVec;
  
  public abstract class Supports implements Relation {
  
      private Encoding encoding;
  
      private final int arity;
  
      private int[][] tuples;
  
      private int lastmatch;
  
      private Map<Evaluable, Integer> mtuple;
  
      public Supports(int arity, int nbtuples) {
          this.arity = arity;
          tuples = new int[nbtuples][];
      }
  
      public void addTuple(int index, int[] tuple) {
          tuples[index] = tuple;
      }
  
      public int arity() {
          return arity;
      }
  
      public void toClause(ISolver solver, IVec<Var> scope, IVec<Evaluable> vars)
              throws ContradictionException {
          assert vars.size() == 0;
          assert scope.size() == arity;
          int[] tuple = new int[scope.size()];
          mtuple = new HashMap<Evaluable, Integer>();
          lastmatch = -1;
          encoding = chooseEncoding(scope);
          encoding.onInit(solver, scope);
          find(tuple, 0, scope, solver);
          encoding.onFinish(solver, scope);
      }
  
      protected abstract Encoding chooseEncoding(IVec<Var> scope);
  
      private void find(int[] tuple, int n, IVec<Var> scope, ISolver solver)
              throws ContradictionException {
          if (n == scope.size()) {
              assert mtuple.size() == n;
              if (notPresent(tuple)) {
                  encoding.onNogood(solver, scope, mtuple);
              } else {
                  encoding.onSupport(solver, scope, mtuple);
              }
          } else {
              Domain domain = scope.get(n).domain();
              for (int i = 0; i < domain.size(); i++) {
                  tuple[n] = domain.get(i);
                  mtuple.put(scope.get(n), tuple[n]);
                  find(tuple, n + 1, scope, solver);
              }
              mtuple.remove(scope.get(n));
  
          }
  
      }
  
      private boolean notPresent(int[] tuple) {
          // System.out.println("Checking:" + Arrays.asList(tuple));
          // find the first tuple begining with the same
          // initial number
          int i = lastmatch + 1;
          int j = 0;
         final int[][] ltuples = tuples;
         int searchedvalue, currentvalue;
         while (i < ltuples.length && j < tuple.length) {
             searchedvalue = ltuples[i][j];
             currentvalue = tuple[j];
             if (searchedvalue < currentvalue) {
                 i++;
                 j = 0;
                 continue;
             }
             if (searchedvalue > currentvalue)
                 return true;
             j++;
         }
         if (j == tuple.length) {
             lastmatch = i;
             return false;
         }
         return true;
     }
 }