/*
    * 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.giraph.zk;
  
  import java.util.concurrent.TimeUnit;
  import java.util.concurrent.locks.Condition;
  import java.util.concurrent.locks.Lock;
  import java.util.concurrent.locks.ReentrantLock;
  
  import org.apache.giraph.time.SystemTime;
  import org.apache.giraph.time.Time;
  import org.apache.hadoop.util.Progressable;
  import org.apache.log4j.Logger;
  
  /**
   * A lock with a predicate that was be used to synchronize events and keep the
   * job context updated while waiting.
   */
  public class PredicateLock implements BspEvent {
    /** Class logger */
    private static final Logger LOG = Logger.getLogger(PredicateLock.class);
    /** Default msecs to refresh the progress meter */
    private static final int DEFAULT_MSEC_PERIOD = 10000;
    /** Progressable for reporting progress (Job context) */
    protected final Progressable progressable;
    /** Actual mses to refresh the progress meter */
    private final int msecPeriod;
    /** Lock */
    private Lock lock = new ReentrantLock();
    /** Condition associated with lock */
    private Condition cond = lock.newCondition();
    /** Predicate */
    private boolean eventOccurred = false;
    /** Keeps track of the time */
    private final Time time;
  
    /**
     * Constructor with default values.
     *
     * @param progressable used to report progress() (usually a Mapper.Context)
     */
    public PredicateLock(Progressable progressable) {
      this(progressable, DEFAULT_MSEC_PERIOD, SystemTime.get());
    }
  
    /**
     * Constructor.
     *
     * @param progressable used to report progress() (usually a Mapper.Context)
     * @param msecPeriod Msecs between progress reports
     * @param time Time implementation
     */
    public PredicateLock(Progressable progressable, int msecPeriod, Time time) {
      this.progressable = progressable;
      this.msecPeriod = msecPeriod;
      this.time = time;
    }
  
    @Override
    public void reset() {
      lock.lock();
      try {
        eventOccurred = false;
      } finally {
        lock.unlock();
      }
    }
  
    @Override
    public void signal() {
      lock.lock();
      try {
        eventOccurred = true;
        cond.signalAll();
      } finally {
        lock.unlock();
      }
    }
  
    @Override
    public boolean waitMsecs(int msecs) {
      if (msecs < 0) {
        throw new RuntimeException("waitMsecs: msecs cannot be negative!");
     }
     long maxMsecs = time.getMilliseconds() + msecs;
     int curMsecTimeout = 0;
     lock.lock();
     try {
       while (!eventOccurred) {
         curMsecTimeout =
             Math.min(msecs, msecPeriod);
         if (LOG.isDebugEnabled()) {
           LOG.debug("waitMsecs: Wait for " + curMsecTimeout);
         }
         try {
           boolean signaled =
               cond.await(curMsecTimeout, TimeUnit.MILLISECONDS);
           if (LOG.isDebugEnabled()) {
             LOG.debug("waitMsecs: Got timed signaled of " +
               signaled);
           }
         } catch (InterruptedException e) {
           throw new IllegalStateException(
             "waitMsecs: Caught interrupted " +
             "exception on cond.await() " +
             curMsecTimeout, e);
         }
         if (time.getMilliseconds() > maxMsecs) {
           return false;
         }
         msecs = Math.max(0, msecs - curMsecTimeout);
         progressable.progress(); // go around again
       }
     } finally {
       lock.unlock();
     }
     return true;
   }
 
   @Override
   public void waitForTimeoutOrFail(long timeout) {
     long t0 = System.currentTimeMillis();
     while (!waitMsecs(msecPeriod)) {
       if (System.currentTimeMillis() > t0 + timeout) {
         throw new RuntimeException("Timeout waiting");
       }
       progressable.progress();
     }
   }
 }