/**
 * 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.apex.malhar.lib.io.jms;

import java.io.IOException;
import java.util.Map;
import java.util.Set;
import java.util.concurrent.ArrayBlockingQueue;
import java.util.concurrent.atomic.AtomicReference;

import javax.jms.ExceptionListener;
import javax.jms.JMSException;
import javax.jms.Message;
import javax.jms.MessageConsumer;
import javax.jms.MessageListener;
import javax.jms.MessageProducer;
import javax.jms.Session;
import javax.jms.Topic;
import javax.validation.constraints.Min;
import javax.validation.constraints.NotNull;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import org.apache.apex.malhar.lib.counters.BasicCounters;
import org.apache.apex.malhar.lib.wal.FSWindowDataManager;
import org.apache.apex.malhar.lib.wal.WindowDataManager;
import org.apache.commons.lang.mutable.MutableLong;

import com.google.common.base.Throwables;
import com.google.common.collect.Maps;
import com.google.common.collect.Sets;

import com.datatorrent.api.Context;
import com.datatorrent.api.Context.OperatorContext;
import com.datatorrent.api.DefaultOutputPort;
import com.datatorrent.api.InputOperator;
import com.datatorrent.api.Operator;
import com.datatorrent.api.Operator.ActivationListener;
import com.datatorrent.api.annotation.OperatorAnnotation;

/**
 * This is the base implementation of a JMS input operator.<br/>
 * Subclasses must implement the method that converts JMS messages into tuples for emission.
 * <p/>
 * The operator acts as a listener for JMS messages. When there is a message available in the message bus,
 * {@link #onMessage(Message)} is called which buffers the message into a holding buffer. This is asynchronous.<br/>
 * {@link #emitTuples()} retrieves messages from holding buffer and processes them.
 * <p/>
 * Important: The {@link FSWindowDataManager} makes the operator fault tolerant as
 * well as idempotent. If {@link WindowDataManager.NoopWindowDataManager} is set on the operator then
 * it will not be fault-tolerant as well.
 * <p/>
 * Configurations:<br/>
 * <b>bufferSize</b>: Controls the holding buffer size.<br/>
 * <b>consumerName</b>: Name that identifies the subscription.<br/>
 *
 * @param <T> type of tuple emitted
 * @displayName Abstract JMS Input
 * @category Messaging
 * @tags jms, input operator
 * @since 0.3.2
 */
@OperatorAnnotation(checkpointableWithinAppWindow = false)
public abstract class AbstractJMSInputOperator<T> extends JMSBase
    implements InputOperator, ActivationListener<OperatorContext>, MessageListener, ExceptionListener,
    Operator.IdleTimeHandler, Operator.CheckpointListener, Operator.CheckpointNotificationListener
{
  protected static final int DEFAULT_BUFFER_SIZE = 10 * 1024; // 10k

  //Configurations:
  @Min(1)
  protected int bufferSize = DEFAULT_BUFFER_SIZE;
  private String consumerName;

  protected transient ArrayBlockingQueue<Message> holdingBuffer;
  protected final transient Map<String, T> currentWindowRecoveryState;

  protected transient Message lastMsg;

  private transient MessageProducer replyProducer;
  private transient MessageConsumer consumer;

  @NotNull
  private final BasicCounters<MutableLong> counters;
  private transient Context.OperatorContext context;
  private transient long spinMillis;

  private final transient AtomicReference<Throwable> throwable;

  @NotNull
  protected WindowDataManager windowDataManager;
  protected transient long currentWindowId;
  protected transient int emitCount;

  private final transient Set<String> pendingAck;
  private final transient Lock lock;

  public final transient DefaultOutputPort<T> output = new DefaultOutputPort<T>();

  public AbstractJMSInputOperator()
  {
    counters = new BasicCounters<MutableLong>(MutableLong.class);
    throwable = new AtomicReference<Throwable>();
    pendingAck = Sets.newHashSet();
    windowDataManager = new FSWindowDataManager();

    lock = new Lock();

    //Recovery state is a linked hash map to maintain the order of tuples.
    currentWindowRecoveryState = Maps.newLinkedHashMap();
    holdingBuffer = new ArrayBlockingQueue<Message>(bufferSize)
    {
      private static final long serialVersionUID = 201411151139L;

      @SuppressWarnings("Contract")
      @Override
      public boolean add(Message message)
      {
        synchronized (lock) {
          try {
            return messageConsumed(message) && super.add(message);
          } catch (JMSException e) {
            LOG.error("message consumption", e);
            throwable.set(e);
            throw new RuntimeException(e);
          }
        }
      }
    };
  }

  /**
   * Implementation of {@link MessageListener} interface.<br/>
   * Whenever there is message available in the message bus this will get called.
   *
   * @param message
   */
  @Override
  public final void onMessage(Message message)
  {
    holdingBuffer.add(message);
    sendReply(message);
  }

  /**
   * If getJMSReplyTo is set then send message back to reply producer.
   *
   * @param message
   */
  protected void sendReply(Message message)
  {
    try {
      if (message.getJMSReplyTo() != null) { // Send reply only if the replyTo destination is set
        replyProducer.send(message.getJMSReplyTo(),
            getSession().createTextMessage("Reply: " + message.getJMSMessageID()));
      }
    } catch (JMSException ex) {
      LOG.error(ex.getLocalizedMessage());
      throwable.set(ex);
      throw new RuntimeException(ex);
    }
  }

  /**
   * Implementation of {@link ExceptionListener}
   *
   * @param ex
   */
  @Override
  public void onException(JMSException ex)
  {
    cleanup();
    LOG.error(ex.getLocalizedMessage());
    throwable.set(ex);
    throw new RuntimeException(ex);
  }

  @Override
  public void setup(OperatorContext context)
  {
    this.context = context;
    spinMillis = context.getValue(OperatorContext.SPIN_MILLIS);
    counters.setCounter(CounterKeys.RECEIVED, new MutableLong());
    counters.setCounter(CounterKeys.REDELIVERED, new MutableLong());
    windowDataManager.setup(context);
  }

  /**
   * This method is called when a message is added to {@link #holdingBuffer} and can be overwritten by subclasses
   * if required. This is called by the JMS thread not Operator thread.
   *
   * @param message
   * @return message is accepted.
   * @throws javax.jms.JMSException
   */
  protected boolean messageConsumed(Message message) throws JMSException
  {
    if (message.getJMSRedelivered() && pendingAck.contains(message.getJMSMessageID())) {
      counters.getCounter(CounterKeys.REDELIVERED).increment();
      LOG.warn("IGNORING: Redelivered Message {}", message.getJMSMessageID());
      return false;
    }
    pendingAck.add(message.getJMSMessageID());
    MutableLong receivedCt = counters.getCounter(CounterKeys.RECEIVED);
    receivedCt.increment();
    LOG.debug("message id: {} buffer size: {} received: {}", message.getJMSMessageID(), holdingBuffer.size(),
        receivedCt.longValue());
    return true;
  }

  /**
   * Implement ActivationListener Interface.
   * @param ctx
   */
  @Override
  public void activate(OperatorContext ctx)
  {
    try {
      super.createConnection();
      replyProducer = getSession().createProducer(null);

      consumer = (isDurable() && isTopic()) ?
          getSession().createDurableSubscriber((Topic)getDestination(), consumerName) :
          getSession().createConsumer(getDestination());
      consumer.setMessageListener(this);
    } catch (JMSException ex) {
      throw new RuntimeException(ex);
    }
  }

  /**
   * Implementation of {@link Operator} interface.
   */
  @Override
  public void beginWindow(long windowId)
  {
    currentWindowId = windowId;
    if (windowId <= windowDataManager.getLargestCompletedWindow()) {
      replay(windowId);
    }
  }

  protected void replay(long windowId)
  {
    try {
      @SuppressWarnings("unchecked")
      Map<String, T> recoveredData = (Map<String, T>)windowDataManager.retrieve(windowId);
      if (recoveredData == null) {
        return;
      }
      for (Map.Entry<String, T> recoveredEntry : recoveredData.entrySet()) {
        /*
          It is important to add the recovered message ids to the pendingAck set because there is no guarantee
          that acknowledgement completed after state was persisted by windowDataManager. In that case, the messages are
          re-delivered by the message bus. Therefore, we compare each message against this set and ignore re-delivered
          messages.
         */
        pendingAck.add(recoveredEntry.getKey());
        emit(recoveredEntry.getValue());
      }
    } catch (IOException e) {
      throw new RuntimeException("replay", e);
    }
  }

  @Override
  public void emitTuples()
  {
    if (currentWindowId <= windowDataManager.getLargestCompletedWindow()) {
      return;
    }

    Message msg;
    while (emitCount < bufferSize && (msg = holdingBuffer.poll()) != null) {
      processMessage(msg);
      emitCount++;
      lastMsg = msg;
    }
  }

  /**
   * Process jms message.
   *
   * @param message
   */
  protected void processMessage(Message message)
  {
    try {
      T payload = convert(message);
      if (payload != null) {
        currentWindowRecoveryState.put(message.getJMSMessageID(), payload);
        emit(payload);
      }
    } catch (JMSException e) {
      throw new RuntimeException("processing msg", e);
    }
  }

  @Override
  public void handleIdleTime()
  {
    Throwable lthrowable = throwable.get();
    if (lthrowable == null) {
      /* nothing to do here, so sleep for a while to avoid busy loop */
      try {
        Thread.sleep(spinMillis);
      } catch (InterruptedException ie) {
        throw new RuntimeException(ie);
      }
    } else {
      Throwables.propagate(lthrowable);
    }
  }

  /**
   * JMS API has a drawback that it only allows acknowledgement/commitment of all the messages which have been consumed
   * in a session instead of all the messages received till a particular message.<br/>
   *
   * This creates complications with recovery/idempotency as we need to ensure that the messages that are being
   * acknowledged have been persisted because they wouldn't be redelivered. Also if they are persisted then
   * they shouldn't be re-delivered because that would cause duplicates.<br/>
   *
   * This is why when recovery data is persisted and messages are acknowledged, the thread that consumes message is
   * blocked.<br/>
   */
  @Override
  public void endWindow()
  {
    if (currentWindowId > windowDataManager.getLargestCompletedWindow()) {
      synchronized (lock) {
        try {
          //No more messages can be consumed now. so we will call emit tuples once more
          //so that any pending messages can be emitted.
          Message msg;
          while ((msg = holdingBuffer.poll()) != null) {
            processMessage(msg);
            emitCount++;
            lastMsg = msg;
          }
          windowDataManager.save(currentWindowRecoveryState, currentWindowId);
          currentWindowRecoveryState.clear();
          if (lastMsg != null) {
            acknowledge();
          }
          pendingAck.clear();
        } catch (Throwable t) {
          /*
            When acknowledgement fails after state is persisted by windowDataManager, then this window is considered
            as completed by the operator instance after recovery. However, since the acknowledgement failed, the
            messages will be re-sent by the message bus. In order to address that, while re-playing, we add the messages
            to the pendingAck set. When these messages are re-delivered, we compare it against this set and ignore them
            if there id is already in the set.
          */
          Throwables.propagate(t);
        }
      }
      emitCount = 0; //reset emit count
    } else if (currentWindowId < windowDataManager.getLargestCompletedWindow()) {
      //pendingAck is not cleared for the last replayed window of this operator. This is because there is
      //still a chance that in the previous run the operator crashed after saving the state but before acknowledgement.
      pendingAck.clear();
    }

    context.setCounters(counters);
  }

  /**
   * Commit/Acknowledge messages that have been received.<br/>
   * @throws javax.jms.JMSException
   */
  protected void acknowledge() throws JMSException
  {
    if (isTransacted()) {
      getSession().commit();
    } else if (getSessionAckMode(getAckMode()) == Session.CLIENT_ACKNOWLEDGE) {
      lastMsg.acknowledge(); // acknowledge all consumed messages till now
    }
  }

  @Override
  public void beforeCheckpoint(long windowId)
  {
  }

  @Override
  public void checkpointed(long windowId)
  {
  }

  @Override
  public void committed(long windowId)
  {
    try {
      windowDataManager.committed(windowId);
    } catch (IOException e) {
      throw new RuntimeException("committing", e);
    }
  }

  @Override
  public void deactivate()
  {
    cleanup();
  }

  @Override
  protected void cleanup()
  {
    try {
      consumer.setMessageListener(null);
      replyProducer.close();
      replyProducer = null;
      consumer.close();
      consumer = null;

      super.cleanup();
    } catch (JMSException ex) {
      throw new RuntimeException("at cleanup", ex);
    }
  }

  @Override
  public void teardown()
  {
    windowDataManager.teardown();
  }

  /**
   * Converts a {@link Message} to type T which is emitted.
   *
   * @param message
   * @return newly constructed tuple from the message.
   * @throws javax.jms.JMSException
   */
  protected abstract T convert(Message message) throws JMSException;

  /**
   * @return the bufferSize
   */
  public int getBufferSize()
  {
    return bufferSize;
  }

  /**
   * Sets the number of tuples emitted in each burst.
   *
   * @param bufferSize the number of tuples to emit in each burst.
   */
  public void setBufferSize(int bufferSize)
  {
    this.bufferSize = bufferSize;
  }

  /**
   * @return the consumer name
   */
  public String getConsumerName()
  {
    return consumerName;
  }

  /**
   * Sets the name for the consumer.
   *
   * @param consumerName- the name for the consumer
   */
  public void setConsumerName(String consumerName)
  {
    this.consumerName = consumerName;
  }

  /**
   * Sets this idempotent storage manager.
   *
   * @param storageManager
   */
  public void setWindowDataManager(WindowDataManager storageManager)
  {
    this.windowDataManager = storageManager;
  }

  /**
   * @return the idempotent storage manager.
   */
  public WindowDataManager getWindowDataManager()
  {
    return this.windowDataManager;
  }

  /**
   * Sets this transacted value
   *
   * @param value    new value for transacted
   */
  public void setTransacted(boolean value)
  {
    transacted = value;
  }

  protected abstract void emit(T payload);

  public static enum CounterKeys
  {
    RECEIVED, REDELIVERED
  }

  private static class Lock
  {
  }

  private static final Logger LOG = LoggerFactory.getLogger(AbstractJMSInputOperator.class);
}