/**
 * 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.hadoop.mapreduce.lib.jobcontrol;

import java.io.IOException;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Hashtable;
import java.util.List;
import java.util.Map;

import org.apache.hadoop.mapreduce.lib.jobcontrol.ControlledJob.State;

/** 
 *  This class encapsulates a set of MapReduce jobs and its dependency.
 *   
 *  It tracks the states of the jobs by placing them into different tables
 *  according to their states. 
 *  
 *  This class provides APIs for the client app to add a job to the group 
 *  and to get the jobs in the group in different states. When a job is 
 *  added, an ID unique to the group is assigned to the job. 
 *  
 *  This class has a thread that submits jobs when they become ready, 
 *  monitors the states of the running jobs, and updates the states of jobs
 *  based on the state changes of their depending jobs states. The class 
 *  provides APIs for suspending/resuming the thread, and 
 *  for stopping the thread.
 *  
 */
public class JobControl implements Runnable {

  // The thread can be in one of the following state
  public static enum ThreadState {RUNNING, SUSPENDED,STOPPED, STOPPING, READY};
	
  private ThreadState runnerState;			// the thread state
	
  private Map<String, ControlledJob> waitingJobs;
  private Map<String, ControlledJob> readyJobs;
  private Map<String, ControlledJob> runningJobs;
  private Map<String, ControlledJob> successfulJobs;
  private Map<String, ControlledJob> failedJobs;
	
  private long nextJobID;
  private String groupName;
	
  /** 
   * Construct a job control for a group of jobs.
   * @param groupName a name identifying this group
   */
  public JobControl(String groupName) {
    this.waitingJobs = new Hashtable<String, ControlledJob>();
    this.readyJobs = new Hashtable<String, ControlledJob>();
    this.runningJobs = new Hashtable<String, ControlledJob>();
    this.successfulJobs = new Hashtable<String, ControlledJob>();
    this.failedJobs = new Hashtable<String, ControlledJob>();
    this.nextJobID = -1;
    this.groupName = groupName;
    this.runnerState = ThreadState.READY;
  }
	
  private static List<ControlledJob> toList(
                   Map<String, ControlledJob> jobs) {
    ArrayList<ControlledJob> retv = new ArrayList<ControlledJob>();
    synchronized (jobs) {
      for (ControlledJob job : jobs.values()) {
        retv.add(job);
      }
    }
    return retv;
  }
	
  /**
   * @return the jobs in the waiting state
   */
  public List<ControlledJob> getWaitingJobList() {
    return toList(this.waitingJobs);
  }
	
  /**
   * @return the jobs in the running state
   */
  public List<ControlledJob> getRunningJobList() {
    return toList(this.runningJobs);
  }
	
  /**
   * @return the jobs in the ready state
   */
  public List<ControlledJob> getReadyJobsList() {
    return toList(this.readyJobs);
  }
	
  /**
   * @return the jobs in the success state
   */
  public List<ControlledJob> getSuccessfulJobList() {
    return toList(this.successfulJobs);
  }
	
  public List<ControlledJob> getFailedJobList() {
    return toList(this.failedJobs);
  }
	
  private String getNextJobID() {
    nextJobID += 1;
    return this.groupName + this.nextJobID;
  }
	
  private static void addToQueue(ControlledJob aJob, 
                                 Map<String, ControlledJob> queue) {
    synchronized(queue) {
      queue.put(aJob.getJobID(), aJob);
    }		
  }
	
  private void addToQueue(ControlledJob aJob) {
    Map<String, ControlledJob> queue = getQueue(aJob.getJobState());
    addToQueue(aJob, queue);	
  }
	
  private Map<String, ControlledJob> getQueue(State state) {
    Map<String, ControlledJob> retv = null;
    if (state == State.WAITING) {
      retv = this.waitingJobs;
    } else if (state == State.READY) {
      retv = this.readyJobs;
    } else if (state == State.RUNNING) {
      retv = this.runningJobs;
    } else if (state == State.SUCCESS) {
      retv = this.successfulJobs;
    } else if (state == State.FAILED || state == State.DEPENDENT_FAILED) {
      retv = this.failedJobs;
    } 
    return retv;
  }

  /**
   * Add a new job.
   * @param aJob the new job
   */
  synchronized public String addJob(ControlledJob aJob) {
    String id = this.getNextJobID();
    aJob.setJobID(id);
    aJob.setJobState(State.WAITING);
    this.addToQueue(aJob);
    return id;	
  }
	
  /**
   * Add a collection of jobs
   * 
   * @param jobs
   */
  public void addJobCollection(Collection<ControlledJob> jobs) {
    for (ControlledJob job : jobs) {
      addJob(job);
    }
  }
	
  /**
   * @return the thread state
   */
  public ThreadState getThreadState() {
    return this.runnerState;
  }
	
  /**
   * set the thread state to STOPPING so that the 
   * thread will stop when it wakes up.
   */
  public void stop() {
    this.runnerState = ThreadState.STOPPING;
  }
	
  /**
   * suspend the running thread
   */
  public void suspend () {
    if (this.runnerState == ThreadState.RUNNING) {
      this.runnerState = ThreadState.SUSPENDED;
    }
  }
	
  /**
   * resume the suspended thread
   */
  public void resume () {
    if (this.runnerState == ThreadState.SUSPENDED) {
      this.runnerState = ThreadState.RUNNING;
    }
  }
	
  synchronized private void checkRunningJobs() 
      throws IOException, InterruptedException {
		
    Map<String, ControlledJob> oldJobs = null;
    oldJobs = this.runningJobs;
    this.runningJobs = new Hashtable<String, ControlledJob>();
		
    for (ControlledJob nextJob : oldJobs.values()) {
      nextJob.checkState();
      this.addToQueue(nextJob);
    }
  }
	
  synchronized private void checkWaitingJobs() 
      throws IOException, InterruptedException {
    Map<String, ControlledJob> oldJobs = null;
    oldJobs = this.waitingJobs;
    this.waitingJobs = new Hashtable<String, ControlledJob>();
		
    for (ControlledJob nextJob : oldJobs.values()) {
      nextJob.checkState();
      this.addToQueue(nextJob);
    }
  }
	
  synchronized private void startReadyJobs() {
    Map<String, ControlledJob> oldJobs = null;
    oldJobs = this.readyJobs;
    this.readyJobs = new Hashtable<String, ControlledJob>();
		
    for (ControlledJob nextJob : oldJobs.values()) {
      //Submitting Job to Hadoop
      nextJob.submit();
      this.addToQueue(nextJob);
    }	
  }
	
  synchronized public boolean allFinished() {
    return this.waitingJobs.size() == 0 &&
      this.readyJobs.size() == 0 &&
      this.runningJobs.size() == 0;
  }
	
  /**
   *  The main loop for the thread.
   *  The loop does the following:
   *  	Check the states of the running jobs
   *  	Update the states of waiting jobs
   *  	Submit the jobs in ready state
   */
  public void run() {
    this.runnerState = ThreadState.RUNNING;
    while (true) {
      while (this.runnerState == ThreadState.SUSPENDED) {
        try {
          Thread.sleep(5000);
        }
        catch (Exception e) {
					
        }
      }
      try {
        checkRunningJobs();	
        checkWaitingJobs();
        startReadyJobs();
      } catch (Exception e) {
  	    this.runnerState = ThreadState.STOPPED;
      }
      if (this.runnerState != ThreadState.RUNNING && 
          this.runnerState != ThreadState.SUSPENDED) {
        break;
      }
      try {
        Thread.sleep(5000);
      }
      catch (Exception e) {
				
      }
      if (this.runnerState != ThreadState.RUNNING && 
          this.runnerState != ThreadState.SUSPENDED) {
        break;
      }
    }
    this.runnerState = ThreadState.STOPPED;
  }

}