/**
 * Licensed to Cloudera, Inc. under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  Cloudera, Inc. 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 com.cloudera.flume.handlers.debug;

import java.io.IOException;

import com.cloudera.flume.conf.SourceFactory.SourceBuilder;
import com.cloudera.flume.core.Event;
import com.cloudera.flume.core.EventSource;
import com.google.common.base.Preconditions;

/**
 * This source does absolutely nothing.
 */
public class NullSource extends EventSource.Base {

  @Override
  public void close() throws IOException {
  }

  @Override
  /**
   * Returning null means end of stream.
   */
  public Event next() throws IOException {
    return null;
  }

  @Override
  public void open() throws IOException {
  }

  public static SourceBuilder builder() {
    return new SourceBuilder() {
      @Override
      public EventSource build(String... argv) {
        Preconditions.checkArgument(argv.length == 0, "usage: null");
        return new NullSource();
      }
    };
  }

}