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/*
 *  Main authors:
 *     Christian Schulte <schulte@gecode.org>
 *
 *  Copyright:
 *     Christian Schulte, 2003
 *
 *  Last modified:
 *     $Date: 2006-03-21 16:46:51 +0100 (Tue, 21 Mar 2006) $ by $Author: schulte $
 *     $Revision: 3093 $
 *
 *  This file is part of Gecode, the generic constraint
 *  development environment:
 *     http://www.gecode.org
 *
 *  See the file "LICENSE" for information on usage and
 *  redistribution of this file, and for a
 *     DISCLAIMER OF ALL WARRANTIES.
 *
 */

namespace Gecode { namespace Int { namespace Distinct {

  /*
   * Eliminating singleton variables
   *
   */
  template <class View, bool complete>
  ExecStatus
  prop_val(Space* home, ViewArray<View>& x) {
    assert(x.size() > 1);
    int n = x.size();

    GECODE_AUTOARRAY(int, stack, n);
    int* c_v = &stack[0];
    // c_n is the current number of values on stack
    int c_n = 0;

    // Collect all assigned variables on stack
    for (int i = n; i--; )
      if (x[i].assigned()) {
        c_v[c_n++]=x[i].val(); x[i]=x[--n];
      }

    // The number of trips
    int t = 0;
    do {
      t++;
      if (!complete && (t > 16)) {
        // Give up after sixteeen iterations, but the values must be
        // propagated first
        // Maybe we are lucky in that this iteration does the trick...
        ExecStatus es = ES_FIX;
        while (c_n > 0) {
          int v = c_v[--c_n];
          // Check whether value is on stack only once
          for (int i = c_n; i--; )
            if (c_v[i] == v)
              goto failed;
          // Tell and do not collect new values
          for (int i = n; i--; ) {
            ModEvent me = x[i].nq(home,v);
            if (me_failed(me))
              goto failed;
            if (me == ME_INT_VAL)
              es = ES_NOFIX;
          }
        }
        x.size(n);
        return es;
      }
      if (c_n > 31) {
        // Many values, use full domain operation
        IntSet d(&c_v[0],c_n);
        // Check for failure
        unsigned int s = 0;
        for (int i = d.size(); i--; )
          s += d.width(i);
        // If the size s of d is different from the number of values,
        // a value must have appeared multiply: failure
        if (s != static_cast<unsigned int>(c_n))
          goto failed;
        // We do not need the values on the stack any longer, reset
        c_n = 0;
        // Tell and collect new values
        for (int i = n; i--; )
          if ((d.min() <= x[i].max()) && (d.max() >= x[i].min())) {
            IntSetRanges dr(d);
            ModEvent me = x[i].minus(home,dr);
            if (me_failed(me))
              goto failed;
            if (me == ME_INT_VAL) {
              c_v[c_n++]=x[i].val(); x[i]=x[--n];
            }
          }
      } else {
        // Values for next iteration
        int* n_v = &c_v[c_n];
        // Stack top for the next iteration
        int n_n = 0;
        while (c_n > 0) {
          int v = c_v[--c_n];
          // Check whether value is not on current stack
          for (int i = c_n; i--; )
            if (c_v[i] == v)
              goto failed;
          // Check whether value is not on next stack
          for (int i = n_n; i--; )
            if (n_v[i] == v)
              goto failed;
          // Tell and collect new values
          for (int i = n; i--; ) {
            ModEvent me = x[i].nq(home,v);
            if (me_failed(me))
              goto failed;
            if (me == ME_INT_VAL) {
              n_v[n_n++]=x[i].val(); x[i]=x[--n];
            }
          }
        }
        c_v = n_v; c_n = n_n;
      }
    } while (c_n > 0);
    x.size(n);
    return (n < 2) ? ES_SUBSUMED : ES_FIX;
  failed:
    x.size(0);
    return ES_FAILED;
  }


  /*
   * The propagator proper
   *
   */
  template <class View>
  forceinline
  Val<View>::Val(Space* home, ViewArray<View>& x)
    : NaryPropagator<View,PC_INT_VAL>(home,x) {}

  template <class View>
  forceinline
  Val<View>::Val(Space* home, bool share, Val<View>& p)
    : NaryPropagator<View,PC_INT_VAL>(home,share,p) {}

  template <class View>
  Actor*
  Val<View>::copy(Space* home, bool share) {
    return new (home) Val<View>(home,share,*this);
  }

  template <class View>
  ExecStatus
  Val<View>::propagate(Space* home) {
    return prop_val<View,true>(home,x);
  }

  template <class View>
  ExecStatus
  Val<View>::post(Space* home, ViewArray<View>& x) {
    if (x.size() == 2)
      return Rel::Nq<View>::post(home,x[0],x[1]);
    if (x.size() > 2)
      (void) new (home) Val<View>(home,x);
    return ES_OK;
  }

}}}

// STATISTICS: int-prop