/**
 * Copyright (C) 2015 DataTorrent, Inc.
 *
 * 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 com.datatorrent.api;

import java.util.Iterator;
import java.util.ServiceLoader;

import org.apache.hadoop.conf.Configuration;

/**
 * Local mode execution for single application
 *
 * @since 0.3.2
 */
public abstract class LocalMode
{

  /**
   * <p>
   * getDAG.</p>
   *
   * @return
   */
  abstract public DAG getDAG();

  /**
   * <p>
   * cloneDAG.</p>
   *
   * @return
   * @throws java.lang.Exception
   */
  abstract public DAG cloneDAG() throws Exception;

  /**
   * Build the logical plan through the given streaming application instance and/or from configuration.
   * <p>
   * The plan will be constructed through {@link StreamingApplication#populateDAG}. If configuration properties are
   * specified, they function as override, as would be the case when launching an application through CLI.
   * <p>
   * This method can also be used to construct the plan declaratively from configuration only, by passing null for the
   * application. In this case the configuration contains all operators and streams.
   * <p>
   *
   * @param app
   * @param conf
   * @return
   * @throws Exception
   * @since 0.3.5
   */
  abstract public DAG prepareDAG(StreamingApplication app, Configuration conf) throws Exception;

  /**
   * <p>
   * getController.</p>
   *
   * @return
   */
  abstract public Controller getController();

  public interface Controller
  {
    public void run();

    public void run(long runMillis);

    public void runAsync();

    public void shutdown();

    public void setHeartbeatMonitoringEnabled(boolean enabled);

  }

  /**
   * <p>
   * newInstance.</p>
   *
   * @return
   */
  public static LocalMode newInstance()
  {
    ServiceLoader<LocalMode> loader = ServiceLoader.load(LocalMode.class);
    Iterator<LocalMode> impl = loader.iterator();
    if (!impl.hasNext()) {
      throw new RuntimeException("No implementation for " + LocalMode.class);
    }
    return impl.next();
  }

  /**
   * Shortcut to run an application. Used for testing.
   *
   * @param app
   * @param runMillis
   */
  public static void runApp(StreamingApplication app, int runMillis)
  {
    runApp(app, null, runMillis);
  }

  /**
   * Shortcut to run an application with the modified configuration.
   *
   * @param app           - Application to be run
   * @param configuration - Configuration
   * @param runMillis     - The time after which the application will be shutdown; pass 0 to run indefinitely.
   */
  public static void runApp(StreamingApplication app, Configuration configuration, int runMillis)
  {
    LocalMode lma = newInstance();
    app.populateDAG(lma.getDAG(), configuration == null ? new Configuration(false) : configuration);
    LocalMode.Controller lc = lma.getController();
    lc.run(runMillis);
  }

}