/*
 * Copyright (c) 2007-2010 Concurrent, Inc. All Rights Reserved.
 *
 * Project and contact information: http://www.cascading.org/
 *
 * This file is part of the Cascading project.
 *
 * Cascading is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * Cascading 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 General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with Cascading.  If not, see <http://www.gnu.org/licenses/>.
 */

package cascading.tuple;

import java.util.Iterator;

/**
 * Class TupleEntryIterator provides an efficient Iterator for returning {@link TupleEntry} elements in an
 * underlying {@link Tuple} collection.
 */
public class TupleEntryIterator implements Iterator<TupleEntry>
  {
  /** Field entry */
  final TupleEntry entry = new TupleEntry( true );
  /** Field iterator */
  final Iterator[] iterators;
  /** Field currentIterator */
  int currentIterator = 0;

  /**
   * Constructor TupleEntryIterator creates a new TupleEntryIterator instance.
   *
   * @param fields    of type Fields
   * @param iterators of type Iterator
   */
  public TupleEntryIterator( Fields fields, Iterator... iterators )
    {
    this.entry.fields = fields;
    this.iterators = iterators;
    }

  /**
   * Method getFields returns the fields of this TupleEntryIterator object.
   *
   * @return the fields (type Fields) of this TupleEntryIterator object.
   */
  public Fields getFields()
    {
    return entry.fields;
    }

  /**
   * Method getTupleEntry returns the entry of this TupleEntryIterator object.
   * <p/>
   * Since TupleEntry instances are re-used, this entry will inherit a new Tuple
   * on every {@link #next()} call.
   *
   * @return the entry (type TupleEntry) of this TupleEntryIterator object.
   */
  public TupleEntry getTupleEntry()
    {
    return entry;
    }

  /**
   * Method hasNext returns true if there is a next TupleEntry
   *
   * @return boolean
   */
  public boolean hasNext()
    {
    if( iterators.length == currentIterator )
      return false;

    if( iterators[ currentIterator ].hasNext() )
      return true;

    currentIterator++;

    return hasNext();
    }

  /**
   * Method next returns the next TupleEntry.
   *
   * @return TupleEntry
   */
  public TupleEntry next()
    {
    hasNext(); // force roll to next iterator

    entry.setTuple( (Tuple) iterators[ currentIterator ].next() );

    return entry;
    }

  /** Method remove removes the current TypleEntry from the underlying collection. */
  public void remove()
    {
    iterators[ currentIterator ].remove();
    }

  /** Method close closes all underlying resources. */
  public void close()
    {
    for( Iterator iterator : iterators )
      {
      if( iterator instanceof TupleIterator )
        ( (TupleIterator) iterator ).close();
      }
    }
  }