package org.apache.samoa.streams;

/*
 * #%L
 * SAMOA
 * %%
 * Copyright (C) 2014 - 2015 Apache Software Foundation
 * %%
 * 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.
 * #L%
 */

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();
}