/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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.apache.samoa.streams;

import org.apache.samoa.instances.InstancesHeader;
import org.apache.samoa.moa.MOAObject;
import org.apache.samoa.moa.core.Example;

/**
 * Interface representing a data stream of examples.
 * 
 * @author Richard Kirkby (rkirkby@cs.waikato.ac.nz)
 * @version $Revision: 7 $
 */
public interface ExampleStream<E extends Example> extends MOAObject {

  /**
   * Gets the header of this stream. This is useful to know attributes and classes. InstancesHeader is an extension of
   * weka.Instances.
   * 
   * @return the header of this stream
   */
  public InstancesHeader getHeader();

  /**
   * Gets the estimated number of remaining instances in this stream
   * 
   * @return the estimated number of instances to get from this stream
   */
  public long estimatedRemainingInstances();

  /**
   * Gets whether this stream has more instances to output. This is useful when reading streams from files.
   * 
   * @return true if this stream has more instances to output
   */
  public boolean hasMoreInstances();

  /**
   * Gets the next example from this stream.
   * 
   * @return the next example of this stream
   */
  public E nextInstance();

  /**
   * Gets whether this stream can restart.
   * 
   * @return true if this stream can restart
   */
  public boolean isRestartable();

  /**
   * Restarts this stream. It must be similar to starting a new stream from scratch.
   * 
   */
  public void restart();
}