FeaturizerEventStream.java

/**
 * Copyright (C) 2012 cogroo <cogroo@cogroo.org>
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *         http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.cogroo.tools.featurizer;

import java.util.ArrayList;
import java.util.Collections;
import java.util.Iterator;
import java.util.List;

import opennlp.tools.ml.model.Event;
import opennlp.tools.util.AbstractEventStream;
import opennlp.tools.util.ObjectStream;

/**
 * Class for creating an event stream out of data files for training a chunker.
 */
public class FeaturizerEventStream extends AbstractEventStream<FeatureSample> {

  private FeaturizerContextGenerator cg;

  /**
   * Creates a new event stream based on the specified data stream using the
   * specified context generator.
   * 
   * @param d
   *          The data stream for this event stream.
   * @param cg
   *          The context generator which should be used in the creation of
   *          events for this event stream.
   */
  public FeaturizerEventStream(ObjectStream<FeatureSample> d,
      FeaturizerContextGenerator cg) {
	super(d);
    this.cg = cg;
  }

  @Override
  protected Iterator<Event> createEvents(FeatureSample sample) {
    if (sample != null) {
      List<Event> events = new ArrayList<Event>();
      String[] toksArray = sample.getSentence();
      String[] tagsArray = sample.getTags();
      String[] predsArray = sample.getFeatures();
      for (int ei = 0, el = sample.getSentence().length; ei < el; ei++) {
        events.add(new Event(predsArray[ei],
            cg.getContext(ei, toksArray, tagsArray, predsArray)));
      }
      return events.iterator();
    } else {
      return Collections.emptyListIterator();
    }
  }
}