/*
 * Copyright (c) 2009, 2011, 2012, 2015, 2016, 2019 Eike Stepper (Loehne, Germany) and others.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors:
 *    Eike Stepper - initial API and implementation
 */
package org.eclipse.emf.internal.cdo.session.remote;

import org.eclipse.emf.cdo.session.remote.CDORemoteSession;
import org.eclipse.emf.cdo.session.remote.CDORemoteSessionEvent;
import org.eclipse.emf.cdo.session.remote.CDORemoteSessionManager;
import org.eclipse.emf.cdo.session.remote.CDORemoteSessionMessage;

import org.eclipse.net4j.util.collection.ArrayIterator;
import org.eclipse.net4j.util.container.Container;
import org.eclipse.net4j.util.container.ContainerEvent;
import org.eclipse.net4j.util.container.IContainerDelta;
import org.eclipse.net4j.util.event.Event;
import org.eclipse.net4j.util.event.IEvent;

import org.eclipse.emf.spi.cdo.InternalCDORemoteSession;
import org.eclipse.emf.spi.cdo.InternalCDORemoteSessionManager;
import org.eclipse.emf.spi.cdo.InternalCDOSession;

import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.Set;

/**
 * @author Eike Stepper
 */
public class CDORemoteSessionManagerImpl extends Container<CDORemoteSession> implements InternalCDORemoteSessionManager
{
  private static final CDORemoteSession[] NO_REMOTE_SESSIONS = {};

  private InternalCDOSession localSession;

  private boolean forceSubscription;

  private boolean subscribed;

  private Map<Integer, CDORemoteSession> remoteSessions = new HashMap<>();

  public CDORemoteSessionManagerImpl()
  {
  }

  @Override
  public InternalCDOSession getLocalSession()
  {
    return localSession;
  }

  @Override
  public void setLocalSession(InternalCDOSession localSession)
  {
    this.localSession = localSession;
  }

  @Override
  public CDORemoteSession[] getRemoteSessions()
  {
    synchronized (this)
    {
      if (localSession.isActive())
      {
        if (subscribed)
        {
          Collection<CDORemoteSession> values = remoteSessions.values();
          return values.toArray(new CDORemoteSession[values.size()]);
        }

        List<CDORemoteSession> loadedRemoteSessions = localSession.getSessionProtocol().getRemoteSessions(this, false);
        return loadedRemoteSessions.toArray(new CDORemoteSession[loadedRemoteSessions.size()]);
      }

      return NO_REMOTE_SESSIONS;
    }
  }

  @Override
  public CDORemoteSession[] getElements()
  {
    return getRemoteSessions();
  }

  @Override
  public boolean isSubscribed()
  {
    synchronized (this)
    {
      return subscribed;
    }
  }

  @Override
  public boolean isForceSubscription()
  {
    synchronized (this)
    {
      return forceSubscription;
    }
  }

  @Override
  public void setForceSubscription(boolean forceSubscription)
  {
    IEvent[] events = null;
    synchronized (this)
    {
      this.forceSubscription = forceSubscription;
      if (forceSubscription)
      {
        if (!subscribed)
        {
          events = subscribe();
        }
      }
      else
      {
        if (!hasListeners())
        {
          events = unsubscribe();
        }
      }
    }

    fireEvents(events);
  }

  @Override
  public Set<CDORemoteSession> sendMessage(CDORemoteSessionMessage message, CDORemoteSession... recipients)
  {
    return sendMessage(message, new ArrayIterator<>(recipients));
  }

  @Override
  public Set<CDORemoteSession> sendMessage(CDORemoteSessionMessage message, Collection<CDORemoteSession> recipients)
  {
    return sendMessage(message, recipients.iterator());
  }

  private Set<CDORemoteSession> sendMessage(CDORemoteSessionMessage message, Iterator<CDORemoteSession> recipients)
  {
    List<CDORemoteSession> subscribed = new ArrayList<>();
    while (recipients.hasNext())
    {
      CDORemoteSession recipient = recipients.next();
      if (recipient.isSubscribed())
      {
        subscribed.add(recipient);
      }
    }

    if (subscribed.isEmpty())
    {
      return Collections.emptySet();
    }

    Set<Integer> sessionIDs = localSession.getSessionProtocol().sendRemoteMessage(message, subscribed);
    Set<CDORemoteSession> result = new HashSet<>();
    for (CDORemoteSession recipient : subscribed)
    {
      if (sessionIDs.contains(recipient.getSessionID()))
      {
        result.add(recipient);
      }
    }

    return result;
  }

  @Override
  public InternalCDORemoteSession createRemoteSession(int sessionID, String userID, boolean subscribed)
  {
    InternalCDORemoteSession remoteSession = new CDORemoteSessionImpl(this, sessionID, userID);
    remoteSession.setSubscribed(subscribed);
    return remoteSession;
  }

  @Override
  public void handleRemoteSessionOpened(int sessionID, String userID)
  {
    CDORemoteSession remoteSession = createRemoteSession(sessionID, userID, false);
    synchronized (this)
    {
      remoteSessions.put(sessionID, remoteSession);
    }

    fireElementAddedEvent(remoteSession);
  }

  @Override
  public void handleRemoteSessionClosed(int sessionID)
  {
    CDORemoteSession remoteSession = null;
    synchronized (this)
    {
      remoteSession = remoteSessions.remove(sessionID);
    }

    if (remoteSession != null)
    {
      fireElementRemovedEvent(remoteSession);
    }
  }

  @Override
  public void handleRemoteSessionSubscribed(int sessionID, boolean subscribed)
  {
    IEvent event = null;
    synchronized (this)
    {
      InternalCDORemoteSession remoteSession = (InternalCDORemoteSession)remoteSessions.get(sessionID);
      if (remoteSession != null)
      {
        remoteSession.setSubscribed(subscribed);
        event = new SubscriptionChangedEventImpl(remoteSession, subscribed);
      }
    }

    if (event != null)
    {
      fireEvent(event);
    }
  }

  @Override
  public void handleRemoteSessionMessage(int sessionID, final CDORemoteSessionMessage message)
  {
    IEvent event = null;
    synchronized (this)
    {
      final CDORemoteSessionManager source = this;
      final InternalCDORemoteSession remoteSession = (InternalCDORemoteSession)remoteSessions.get(sessionID);
      if (remoteSession != null)
      {
        event = new CDORemoteSessionEvent.MessageReceived()
        {
          @Override
          public CDORemoteSessionManager getSource()
          {
            return source;
          }

          @Override
          public CDORemoteSession getRemoteSession()
          {
            return remoteSession;
          }

          @Override
          public CDORemoteSessionMessage getMessage()
          {
            return message;
          }
        };
      }
    }

    if (event != null)
    {
      fireEvent(event);
    }
  }

  @Override
  protected void firstListenerAdded()
  {
    IEvent[] events = null;
    synchronized (this)
    {
      if (!subscribed)
      {
        events = subscribe();
      }
    }

    fireEvents(events);
  }

  @Override
  protected void lastListenerRemoved()
  {
    IEvent[] events = null;
    synchronized (this)
    {
      if (!forceSubscription)
      {
        events = unsubscribe();
      }
    }

    fireEvents(events);
  }

  /**
   * Needs to be synchronized externally.
   */
  private IEvent[] subscribe()
  {
    List<CDORemoteSession> result = localSession.getSessionProtocol().getRemoteSessions(this, true);
    ContainerEvent<CDORemoteSession> event = new ContainerEvent<>(this);
    for (CDORemoteSession remoteSession : result)
    {
      remoteSessions.put(remoteSession.getSessionID(), remoteSession);
      event.addDelta(remoteSession, IContainerDelta.Kind.ADDED);
    }

    subscribed = true;
    IEvent[] events = { new LocalSubscriptionChangedEventImpl(true), event.isEmpty() ? null : event };
    return events;
  }

  /**
   * Needs to be synchronized externally.
   */
  private IEvent[] unsubscribe()
  {
    if (localSession.isActive())
    {
      localSession.getSessionProtocol().unsubscribeRemoteSessions();
    }

    ContainerEvent<CDORemoteSession> event = new ContainerEvent<>(this);
    for (CDORemoteSession remoteSession : remoteSessions.values())
    {
      event.addDelta(remoteSession, IContainerDelta.Kind.REMOVED);
    }

    remoteSessions.clear();
    subscribed = false;
    IEvent[] events = { new LocalSubscriptionChangedEventImpl(false), event.isEmpty() ? null : event };
    return events;
  }

  private void fireEvents(IEvent[] events)
  {
    if (events != null)
    {
      for (int i = 0; i < events.length; i++)
      {
        IEvent event = events[i];
        if (event != null)
        {
          fireEvent(event);
        }
      }
    }
  }

  /**
   * @author Eike Stepper
   */
  private final class LocalSubscriptionChangedEventImpl extends Event implements LocalSubscriptionChangedEvent
  {
    private static final long serialVersionUID = 1L;

    private boolean subscribed;

    public LocalSubscriptionChangedEventImpl(boolean subscribed)
    {
      super(CDORemoteSessionManagerImpl.this);
      this.subscribed = subscribed;
    }

    @Override
    public CDORemoteSessionManager getSource()
    {
      return (CDORemoteSessionManager)super.getSource();
    }

    @Override
    public boolean isSubscribed()
    {
      return subscribed;
    }
  }

  /**
   * @author Eike Stepper
   */
  private final class SubscriptionChangedEventImpl extends Event implements CDORemoteSessionEvent.SubscriptionChanged
  {
    private static final long serialVersionUID = 1L;

    private InternalCDORemoteSession remoteSession;

    private boolean subscribed;

    public SubscriptionChangedEventImpl(InternalCDORemoteSession remoteSession, boolean subscribed)
    {
      super(CDORemoteSessionManagerImpl.this);
      this.remoteSession = remoteSession;
      this.subscribed = subscribed;
    }

    @Override
    public CDORemoteSessionManager getSource()
    {
      return (CDORemoteSessionManager)super.getSource();
    }

    @Override
    public CDORemoteSession getRemoteSession()
    {
      return remoteSession;
    }

    @Override
    public boolean isSubscribed()
    {
      return subscribed;
    }
  }
}