/**
 *
 * Copyright
 * 2009-2015 Jayway Products AB
 * 2016-2017 Föreningen Sambruk
 *
 * Licensed under AGPL, Version 3.0 (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.gnu.org/licenses/agpl.txt
 *
 * 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 se.streamsource.streamflow.infrastructure.event.application.source.helper;

import org.qi4j.api.configuration.Configuration;
import org.qi4j.api.io.Output;
import org.qi4j.api.io.Receiver;
import org.qi4j.api.io.Sender;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import se.streamsource.streamflow.infrastructure.event.application.TransactionApplicationEvents;
import se.streamsource.streamflow.infrastructure.event.application.source.ApplicationEventSource;
import se.streamsource.streamflow.infrastructure.event.application.source.ApplicationEventStream;
import se.streamsource.streamflow.infrastructure.event.domain.source.helper.TransactionTrackerConfiguration;

/**
 * Helper that enables a service to easily track transactions. Upon startup
 * the tracker will get all the transactions from the store since the last
 * check, and delegate them to the given Output. It will also register itself
 * with the store so that it can get continuous updates.
 * <p/>
 * Then, as transactions come in from the store, they will be processed in real-time.
 * If a transaction is successfully handled the configuration of the service, which must
 * extend TransactionTrackerConfiguration, will update the marker for the last successfully handled transaction.
 */
public class ApplicationTransactionTracker<ReceiverThrowableType extends Throwable>
{
   private Configuration<? extends TransactionTrackerConfiguration> configuration;
   private Output<TransactionApplicationEvents, ReceiverThrowableType> output;
   private ApplicationEventStream stream;
   private ApplicationEventSource source;
   private boolean started = false;
   private boolean upToSpeed = false;
   private Logger logger;
   private Output<TransactionApplicationEvents, ReceiverThrowableType> trackerOutput;

   public ApplicationTransactionTracker(ApplicationEventStream stream, ApplicationEventSource source,
                                        Configuration<? extends TransactionTrackerConfiguration> configuration,
                                        Output<TransactionApplicationEvents, ReceiverThrowableType> output)
   {
      this.stream = stream;
      this.configuration = configuration;
      this.source = source;
      this.output = output;

      logger = LoggerFactory.getLogger(output.getClass());
   }

   public void start()
   {
      if (!started)
      {
         started = true;

         // Get events since last check
         upToSpeed = true; // Pretend that we are up to speed from now on
         trackerOutput = output();
         try
         {
            source.transactionsAfter(configuration.configuration().lastEventDate().get(), Long.MAX_VALUE).transferTo(trackerOutput);
         } catch (Throwable receiverThrowableType)
         {
            upToSpeed = false;
         }

         stream.registerListener(trackerOutput);
      }
   }

   public void stop()
   {
      if (started)
      {
         started = false;
         stream.unregisterListener(trackerOutput);
         upToSpeed = false;
      }
   }

   private Output<TransactionApplicationEvents, ReceiverThrowableType> output()
   {
      return new Output<TransactionApplicationEvents, ReceiverThrowableType>()
      {
         public <SenderThrowableType extends Throwable> void receiveFrom(final Sender<? extends TransactionApplicationEvents, SenderThrowableType> sender) throws ReceiverThrowableType, SenderThrowableType
         {
         if (!upToSpeed)
            {
               // The tracker has not handled successfully all transactions before,
               // so it needs to get the backlog first

               upToSpeed = true; // Pretend that we are up to speed from now on

               // Get all transactions from last timestamp, including the one in this call
               try
               {
                  source.transactionsAfter(configuration.configuration().lastEventDate().get(), Long.MAX_VALUE).transferTo(trackerOutput);
               } catch (Throwable e)
               {
                  upToSpeed = false;
                  throw (SenderThrowableType) e;
               }
            }

            try
            {
               output.receiveFrom(new Sender<TransactionApplicationEvents, SenderThrowableType>()
               {
                  public <ReceiverThrowableType extends Throwable> void sendTo(final Receiver<? super TransactionApplicationEvents, ReceiverThrowableType> receiver) throws ReceiverThrowableType, SenderThrowableType
                  {
                     sender.sendTo(new Receiver<TransactionApplicationEvents, ReceiverThrowableType>()
                     {
                        public void receive(TransactionApplicationEvents item) throws ReceiverThrowableType
                        {
                           receiver.receive(item);

                           // Events in this transactionDomain were handled successfully so store new marker
                           configuration.configuration().lastEventDate().set(item.timestamp().get());
                           configuration.save();
                        }
                     });
                  }
               });
            } catch (Throwable receiverThrowableType)
            {
               upToSpeed = false;
               throw (ReceiverThrowableType) receiverThrowableType;
            }
         }
      };
   }
}