/*
 * 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.activemq.artemis.core.server.impl;

import java.util.Collections;
import java.util.Map;
import java.util.Set;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ScheduledExecutorService;
import java.util.function.Consumer;

import org.apache.activemq.artemis.api.core.ActiveMQException;
import org.apache.activemq.artemis.api.core.Message;
import org.apache.activemq.artemis.api.core.RoutingType;
import org.apache.activemq.artemis.api.core.SimpleString;
import org.apache.activemq.artemis.core.filter.Filter;
import org.apache.activemq.artemis.core.paging.cursor.PageSubscription;
import org.apache.activemq.artemis.core.persistence.StorageManager;
import org.apache.activemq.artemis.core.postoffice.PostOffice;
import org.apache.activemq.artemis.core.server.ActiveMQServer;
import org.apache.activemq.artemis.core.server.ActiveMQServerLogger;
import org.apache.activemq.artemis.core.server.MessageReference;
import org.apache.activemq.artemis.core.server.Queue;
import org.apache.activemq.artemis.core.server.QueueFactory;
import org.apache.activemq.artemis.core.server.ServerConsumer;
import org.apache.activemq.artemis.core.settings.HierarchicalRepository;
import org.apache.activemq.artemis.core.settings.impl.AddressSettings;
import org.apache.activemq.artemis.core.transaction.Transaction;
import org.apache.activemq.artemis.utils.actors.ArtemisExecutor;

/**
 * A queue that will discard messages if a newer message with the same
 * {@link org.apache.activemq.artemis.core.message.impl.CoreMessage#HDR_LAST_VALUE_NAME} property value. In other words it only retains the last
 * value
 * <p>
 * This is useful for example, for stock prices, where you're only interested in the latest value
 * for a particular stock
 */
@SuppressWarnings("ALL")
public class LastValueQueue extends QueueImpl {

   private final Map<SimpleString, HolderReference> map = new ConcurrentHashMap<>();
   private final SimpleString lastValueKey;

   public LastValueQueue(final long persistenceID,
                         final SimpleString address,
                         final SimpleString name,
                         final Filter filter,
                         final PageSubscription pageSubscription,
                         final SimpleString user,
                         final boolean durable,
                         final boolean temporary,
                         final boolean autoCreated,
                         final RoutingType routingType,
                         final Integer maxConsumers,
                         final Boolean exclusive,
                         final Boolean groupRebalance,
                         final Integer groupBuckets,
                         final SimpleString groupFirstKey,
                         final Integer consumersBeforeDispatch,
                         final Long delayBeforeDispatch,
                         final Boolean purgeOnNoConsumers,
                         final SimpleString lastValueKey,
                         final Boolean nonDestructive,
                         final Boolean autoDelete,
                         final Long autoDeleteDelay,
                         final Long autoDeleteMessageCount,
                         final boolean configurationManaged,
                         final ScheduledExecutorService scheduledExecutor,
                         final PostOffice postOffice,
                         final StorageManager storageManager,
                         final HierarchicalRepository<AddressSettings> addressSettingsRepository,
                         final ArtemisExecutor executor,
                         final ActiveMQServer server,
                         final QueueFactory factory) {
      super(persistenceID, address, name, filter, pageSubscription, user, durable, temporary, autoCreated, routingType, maxConsumers, exclusive, groupRebalance, groupBuckets, groupFirstKey, nonDestructive, consumersBeforeDispatch, delayBeforeDispatch, purgeOnNoConsumers, autoDelete, autoDeleteDelay, autoDeleteMessageCount, configurationManaged, scheduledExecutor, postOffice, storageManager, addressSettingsRepository, executor, server, factory);
      this.lastValueKey = lastValueKey;
   }

   @Override
   public synchronized void addTail(final MessageReference ref, final boolean direct) {
      if (scheduleIfPossible(ref)) {
         return;
      }
      final SimpleString prop = ref.getLastValueProperty();

      if (prop != null) {
         HolderReference hr = map.get(prop);

         if (hr != null) {
            // We need to overwrite the old ref with the new one and ack the old one

            replaceLVQMessage(ref, hr);

            if (isNonDestructive() && hr.isDelivered()) {
               hr.resetDelivered();
               // --------------------------------------------------------------------------------
               // If non Destructive, and if a reference was previously delivered
               // we would not be able to receive this message again
               // unless we reset the iterators
               // The message is not removed, so we can't actually remove it
               // a result of this operation is that previously delivered messages
               // will probably be delivered again.
               // if we ever want to avoid other redeliveries we would have to implement a reset or redeliver
               // operation on the iterator for a single message
               resetAllIterators();
               deliverAsync();
            }

         } else {
            hr = new HolderReference(prop, ref);

            map.put(prop, hr);

            super.addTail(hr, direct);
         }
      } else {
         super.addTail(ref, direct);
      }
   }


   @Override
   public long getMessageCount() {
      if (pageSubscription != null) {
         // messageReferences will have depaged messages which we need to discount from the counter as they are
         // counted on the pageSubscription as well
         return (long) pendingMetrics.getMessageCount() + getScheduledCount() + pageSubscription.getMessageCount();
      } else {
         return (long) pendingMetrics.getMessageCount() + getScheduledCount();
      }
   }

   @Override
   public synchronized void addHead(final MessageReference ref, boolean scheduling) {
      // we first need to check redelivery-delay, as we can't put anything on headers if redelivery-delay
      if (!scheduling && scheduledDeliveryHandler.checkAndSchedule(ref, false)) {
         return;
      }

      SimpleString lastValueProp = ref.getLastValueProperty();

      if (lastValueProp != null) {
         HolderReference hr = map.get(lastValueProp);

         if (hr != null) {
            if (scheduling) {
               // We need to overwrite the old ref with the new one and ack the old one

               replaceLVQMessage(ref, hr);
            } else {
               // We keep the current ref and ack the one we are returning

               super.referenceHandled(ref);

               try {
                  super.acknowledge(ref);
               } catch (Exception e) {
                  ActiveMQServerLogger.LOGGER.errorAckingOldReference(e);
               }
            }
         } else {
            hr = new HolderReference(lastValueProp, ref);

            map.put(lastValueProp, hr);

            super.addHead(hr, scheduling);
         }
      } else {
         super.addHead(ref, scheduling);
      }
   }

   @Override
   public boolean allowsReferenceCallback() {
      return false;
   }

   private void replaceLVQMessage(MessageReference ref, HolderReference hr) {
      MessageReference oldRef = hr.getReference();

      referenceHandled(ref);

      try {
         oldRef.acknowledge(null, AckReason.REPLACED, null);
      } catch (Exception e) {
         ActiveMQServerLogger.LOGGER.errorAckingOldReference(e);
      }

      hr.setReference(ref);
   }

   @Override
   protected void refRemoved(MessageReference ref) {
      if (isNonDestructive()) {
         removeIfCurrent(ref);
      }
      super.refRemoved(ref);
   }

   @Override
   public void acknowledge(final MessageReference ref, final AckReason reason, final ServerConsumer consumer) throws Exception {
      if (isNonDestructive() && reason == AckReason.EXPIRED || reason == AckReason.KILLED ) {
         removeIfCurrent(ref);
      }
      super.acknowledge(ref, reason, consumer);
   }

   @Override
   public synchronized void reload(final MessageReference ref) {
      // repopulate LVQ map & reload proper HolderReferences
      SimpleString lastValueProp = ref.getLastValueProperty();
      if (lastValueProp != null) {
         HolderReference hr = new HolderReference(lastValueProp, ref);
         map.put(lastValueProp, hr);
         super.reload(hr);
      } else {
         super.reload(ref);
      }
   }

   private synchronized void removeIfCurrent(MessageReference ref) {
      SimpleString lastValueProp = ref.getLastValueProperty();
      if (lastValueProp != null) {
         MessageReference current = map.get(lastValueProp);
         if (current == ref) {
            map.remove(lastValueProp);
         }
      }
   }

   @Override
   QueueIterateAction createDeleteMatchingAction(AckReason ackReason) {
      QueueIterateAction queueIterateAction = super.createDeleteMatchingAction(ackReason);
      return new QueueIterateAction() {
         @Override
         public void actMessage(Transaction tx, MessageReference ref) throws Exception {
            removeIfCurrent(ref);
            queueIterateAction.actMessage(tx, ref);
         }
      };
   }




   @Override
   public boolean isLastValue() {
      return true;
   }

   @Override
   public SimpleString getLastValueKey() {
      return lastValueKey;
   }

   public synchronized Set<SimpleString> getLastValueKeys() {
      return Collections.unmodifiableSet(map.keySet());
   }

   private static class HolderReference implements MessageReference {

      private final SimpleString prop;

      private volatile boolean delivered = false;

      private volatile MessageReference ref;

      private long consumerID;

      private boolean hasConsumerID = false;


      public void resetDelivered() {
         delivered = false;
      }

      public boolean isDelivered() {
         return delivered;
      }

      HolderReference(final SimpleString prop, final MessageReference ref) {
         this.prop = prop;

         this.ref = ref;
      }

      @Override
      public void onDelivery(Consumer<? super MessageReference> callback) {
         // HolderReference may be reused among different consumers, so we don't set a callback and won't support Runnables
      }

      MessageReference getReference() {
         return ref;
      }

      @Override
      public void handled() {
         delivered = true;
         // We need to remove the entry from the map just before it gets delivered
         ref.handled();
         if (!ref.getQueue().isNonDestructive()) {
            ((LastValueQueue) ref.getQueue()).removeIfCurrent(this);
         }
      }

      @Override
      public Object getProtocolData() {
         return ref.getProtocolData();
      }

      @Override
      public void setProtocolData(Object data) {
         ref.setProtocolData(data);
      }

      @Override
      public void setAlreadyAcked() {
         ref.setAlreadyAcked();
      }

      @Override
      public boolean isAlreadyAcked() {
         return ref.isAlreadyAcked();
      }

      void setReference(final MessageReference ref) {
         this.ref = ref;
      }

      @Override
      public MessageReference copy(final Queue queue) {
         return ref.copy(queue);
      }

      @Override
      public void decrementDeliveryCount() {
         ref.decrementDeliveryCount();
      }

      @Override
      public int getDeliveryCount() {
         return ref.getDeliveryCount();
      }

      @Override
      public Message getMessage() {
         return ref.getMessage();
      }

      @Override
      public long getMessageID() {
         return ref.getMessageID();
      }

      @Override
      public boolean isDurable() {
         return getMessage().isDurable();
      }

      @Override
      public SimpleString getLastValueProperty() {
         return prop;
      }

      @Override
      public Queue getQueue() {
         return ref.getQueue();
      }

      @Override
      public long getScheduledDeliveryTime() {
         return ref.getScheduledDeliveryTime();
      }

      @Override
      public void incrementDeliveryCount() {
         ref.incrementDeliveryCount();
      }

      @Override
      public void setDeliveryCount(final int deliveryCount) {
         ref.setDeliveryCount(deliveryCount);
      }

      @Override
      public void setScheduledDeliveryTime(final long scheduledDeliveryTime) {
         ref.setScheduledDeliveryTime(scheduledDeliveryTime);
      }

      @Override
      public void acknowledge(Transaction tx) throws Exception {
         ref.acknowledge(tx);
      }

      @Override
      public void acknowledge(Transaction tx, ServerConsumer consumer) throws Exception {
         ref.acknowledge(tx, consumer);
      }

      @Override
      public void acknowledge(Transaction tx, AckReason reason, ServerConsumer consumer) throws Exception {
         ref.acknowledge(tx, reason, consumer);
      }

      @Override
      public void setPersistedCount(int count) {
         ref.setPersistedCount(count);
      }

      @Override
      public int getPersistedCount() {
         return ref.getPersistedCount();
      }

      @Override
      public boolean isPaged() {
         return false;
      }

      /* (non-Javadoc)
       * @see org.apache.activemq.artemis.core.server.MessageReference#acknowledge(org.apache.activemq.artemis.core.server.MessageReference)
       */
      @Override
      public void acknowledge() throws Exception {
         ref.getQueue().acknowledge(this);
      }

      /* (non-Javadoc)
       * @see org.apache.activemq.artemis.core.server.MessageReference#getMessageMemoryEstimate()
       */
      @Override
      public int getMessageMemoryEstimate() {
         return ref.getMessage().getMemoryEstimate();
      }

      @Override
      public void emptyConsumerID() {
         this.hasConsumerID = false;
      }

      @Override
      public void setConsumerId(long consumerID) {
         this.hasConsumerID = true;
         this.consumerID = consumerID;
      }

      @Override
      public boolean hasConsumerId() {
         return hasConsumerID;
      }

      @Override
      public long getConsumerId() {
         if (!this.hasConsumerID) {
            throw new IllegalStateException("consumerID isn't specified: please check hasConsumerId first");
         }
         return this.consumerID;
      }

      @Override
      public long getPersistentSize() throws ActiveMQException {
         return ref.getPersistentSize();
      }

      @Override
      public String toString() {
         return new StringBuilder().append("HolderReference").append("@").append(Integer.toHexString(System.identityHashCode(this))).append("[ref=").append(ref).append("]").toString();
      }
   }

   @Override
   public int hashCode() {
      final int prime = 31;
      int result = super.hashCode();
      result = prime * result + ((map == null) ? 0 : map.hashCode());
      return result;
   }

   @Override
   public boolean equals(Object obj) {
      if (this == obj) {
         return true;
      }
      if (!super.equals(obj)) {
         return false;
      }
      if (!(obj instanceof LastValueQueue)) {
         return false;
      }
      LastValueQueue other = (LastValueQueue) obj;
      if (map == null) {
         if (other.map != null) {
            return false;
         }
      } else if (!map.equals(other.map)) {
         return false;
      }
      return true;
   }
}
