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/*
    This file is part of Sarasvati.

    Sarasvati is free software: you can redistribute it and/or modify
    it under the terms of the GNU Lesser General Public License as
    published by the Free Software Foundation, either version 3 of the
    License, or (at your option) any later version.

    Sarasvati is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU Lesser General Public License for more details.

    You should have received a copy of the GNU Lesser General Public
    License along with Sarasvati.  If not, see .

    Copyright 2009 Paul Lorenz
*/
package com.googlecode.sarasvati.join;

import java.util.ArrayList;
import java.util.List;

import com.googlecode.sarasvati.Arc;
import com.googlecode.sarasvati.ArcToken;
import com.googlecode.sarasvati.Engine;
import com.googlecode.sarasvati.GraphProcess;
import com.googlecode.sarasvati.JoinResult;
import com.googlecode.sarasvati.JoinStrategy;
import com.googlecode.sarasvati.SarasvatiException;
import com.googlecode.sarasvati.TokenSetMember;

/**
 * Implements a join strategy in which nodes will wait for arc tokens to be
 * present on all incoming arcs before completing the join.
 *
 * @author Paul Lorenz
 */
public class AndJoinStrategy implements JoinStrategy
{
  protected List getJoiningArcs(final GraphProcess process, final ArcToken token)
  {
    return process.getGraph().getInputArcs(token.getArc().getEndNode());
  }

  /**
   * Returns the filter to use when joining
   *
   * @param engine Engine may be used by subclass to return different set of nodes
   * @param arcToken The arc token being joined
   *
   * @return The filter to use when joining
   */
  protected ArcTokenFilter getTokenFilter(final Engine engine, final ArcToken arcToken)
  {
    if (!arcToken.isTokenSetMember())
    {
      return NoTokenMembershipsFilter.INSTANCE;
    }

    TokenSetMember tokenSetMember = null;
    for (final TokenSetMember next : arcToken.getTokenSetMemberships())
    {
      if (tokenSetMember == null || tokenSetMember.getTokenSet().getLevel() < next.getTokenSet().getLevel())
      {
        tokenSetMember = next;
      }
    }

    if (tokenSetMember == null)
    {
      throw new SarasvatiException("Arc Token " + arcToken + " was marking as having token set memberships, but didn't.");
    }

    return new TokenSetGroupFilter(tokenSetMember.getTokenSet(), tokenSetMember.getMemberIndex());
  }

  @Override
  public JoinResult performJoin(final Engine engine, final ArcToken token)
  {
    final ArcTokenFilter filter = getTokenFilter(engine, token);
    return performJoin(token, filter);
  }

  public JoinResult performJoin(final ArcToken initiatingToken,
                                final ArcTokenFilter filter)
  {
    final List joinArcs = getJoiningArcs(initiatingToken.getProcess(), initiatingToken);

    final ArrayList tokens = new ArrayList(joinArcs.size());

    for (final Arc arc : joinArcs)
    {
      for (final ArcToken arcToken : initiatingToken.getProcess().getActiveArcTokens())
      {
        if (arcToken.getArc().equals(arc) && filter.isValidForJoin(arcToken))
        {
          tokens.add(arcToken);
          break;
        }
      }
    }

    return joinArcs.size() == tokens.size() ? new CompleteJoinResult(tokens) : IncompleteJoinResult.INSTANCE;
  }
}