/*
 * Copyright (c) 2014 Cisco Systems, Inc. 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
 */

package org.opendaylight.controller.cluster.datastore;

import akka.actor.Props;
import akka.japi.Creator;
import com.google.common.base.Preconditions;
import org.opendaylight.controller.cluster.common.actor.AbstractUntypedActor;
import org.opendaylight.controller.cluster.datastore.messages.DataChanged;
import org.opendaylight.controller.cluster.datastore.messages.DataChangedReply;
import org.opendaylight.controller.cluster.datastore.messages.EnableNotification;
import org.opendaylight.controller.md.sal.common.api.data.AsyncDataChangeEvent;
import org.opendaylight.controller.md.sal.common.api.data.AsyncDataChangeListener;
import org.opendaylight.yangtools.yang.data.api.YangInstanceIdentifier;
import org.opendaylight.yangtools.yang.data.api.schema.NormalizedNode;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

public class DataChangeListener extends AbstractUntypedActor {
    private static final Logger LOG = LoggerFactory.getLogger(DataChangeListener.class);

    private final AsyncDataChangeListener<YangInstanceIdentifier, NormalizedNode<?, ?>> listener;
    private boolean notificationsEnabled = false;

    public DataChangeListener(AsyncDataChangeListener<YangInstanceIdentifier,
                                                      NormalizedNode<?, ?>> listener) {
        this.listener = Preconditions.checkNotNull(listener, "listener should not be null");
    }

    @Override
    public void handleReceive(Object message) throws Exception {
        if(message instanceof DataChanged){
            dataChanged(message);
        } else if(message instanceof EnableNotification){
            enableNotification((EnableNotification) message);
        }
    }

    private void enableNotification(EnableNotification message) {
        notificationsEnabled = message.isEnabled();
        LOG.debug("{} notifications for listener {}", (notificationsEnabled ? "Enabled" : "Disabled"),
                listener);
    }

    private void dataChanged(Object message) {

        // Do nothing if notifications are not enabled
        if(!notificationsEnabled) {
            LOG.debug("Notifications not enabled for listener {} - dropping change notification",
                    listener);
            return;
        }

        DataChanged reply = (DataChanged) message;
        AsyncDataChangeEvent<YangInstanceIdentifier, NormalizedNode<?, ?>> change = reply.getChange();

        LOG.debug("Sending change notification {} to listener {}", change, listener);

        try {
            this.listener.onDataChanged(change);
        } catch (RuntimeException e) {
            LOG.error( String.format( "Error notifying listener %s", this.listener ), e );
        }

        // It seems the sender is never null but it doesn't hurt to check. If the caller passes in
        // a null sender (ActorRef.noSender()), akka translates that to the deadLetters actor.
        if(getSender() != null && !getContext().system().deadLetters().equals(getSender())) {
            getSender().tell(DataChangedReply.INSTANCE, getSelf());
        }
    }

    public static Props props(final AsyncDataChangeListener<YangInstanceIdentifier,
                                                            NormalizedNode<?, ?>> listener) {
        return Props.create(new DataChangeListenerCreator(listener));
    }

    private static class DataChangeListenerCreator implements Creator<DataChangeListener> {
        private static final long serialVersionUID = 1L;

        final AsyncDataChangeListener<YangInstanceIdentifier, NormalizedNode<?, ?>> listener;

        DataChangeListenerCreator(
                AsyncDataChangeListener<YangInstanceIdentifier, NormalizedNode<?, ?>> listener) {
            this.listener = listener;
        }

        @Override
        public DataChangeListener create() throws Exception {
            return new DataChangeListener(listener);
        }
    }
}