/**
 * Copyright (C) FuseSource, Inc.
 * http://fusesource.com
 *
 * Licensed 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.fusesource.fabric.camel;

import org.apache.camel.Consumer;
import org.apache.camel.Processor;
import org.apache.camel.SuspendableService;
import org.apache.camel.impl.DefaultConsumer;
import org.apache.camel.util.ServiceHelper;
import org.fusesource.fabric.groups.GroupListener;
import org.fusesource.fabric.groups.Group;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * A consumer which is only really active while it holds the master lock
 */
public class MasterConsumer extends DefaultConsumer implements GroupListener {
    private static final transient Logger LOG = LoggerFactory.getLogger(MasterConsumer.class);

    private final MasterEndpoint endpoint;
    private final Processor processor;
    private Consumer delegate;
    private SuspendableService delegateService;
    private final Group<CamelNodeState> singleton;

    public MasterConsumer(MasterEndpoint endpoint, Processor processor) {
        super(endpoint, processor);
        this.endpoint = endpoint;
        this.processor = processor;
        MasterComponent component = endpoint.getComponent();
        String path = component.getFabricPath(endpoint.getSingletonId());
        this.singleton = component.createGroup(path);
        this.singleton.add(this);
    }

    @Override
    protected void doStart() throws Exception {
        super.doStart();
        singleton.start();
        CamelNodeState state = new CamelNodeState(endpoint.getSingletonId());
        LOG.debug("Attempting to become master for endpoint: " + endpoint + " in " + endpoint.getCamelContext() + " with singletonID: " + endpoint.getSingletonId());
        singleton.update(state);
    }

    @Override
    protected void doStop() throws Exception {
        super.doStop();
        try {
            stopConsumer();
        } finally {
            singleton.close();
        }
    }

    protected void stopConsumer() throws Exception {
        ServiceHelper.stopService(delegate);
        delegate = null;
        delegateService = null;
    }

    @Override
    protected void doResume() throws Exception {
        if (delegateService != null) {
            delegateService.resume();
        }
        super.doResume();
    }

    @Override
    protected void doSuspend() throws Exception {
        if (delegateService != null) {
            delegateService.suspend();
        }
        super.doSuspend();
    }

    @Override
    public void groupEvent(Group group, GroupEvent event) {
        switch (event) {
            case CONNECTED:
                break;
            case CHANGED:
                if (singleton.isConnected()) {
                    if (singleton.isMaster()) {
                        if (LOG.isDebugEnabled()) {
                            LOG.debug("Master/Standby endpoint is Master for:  " + endpoint + " in " + endpoint.getCamelContext());
                        }
                        onLockOwned();
                    } else {
                        if (LOG.isDebugEnabled()) {
                            LOG.debug("Master/Standby endpoint is Standby for: " + endpoint + " in " + endpoint.getCamelContext());
                        }
                    }
                }
                break;
            case DISCONNECTED:
                try {
                    stopConsumer();
                } catch (Exception e) {
                    LOG.error("Failed to stop master consumer for: " + endpoint + ". Reason: " + e, e);
                }
                break;
        }
    }

    protected void onLockOwned() {
        if (delegate == null) {
            try {
                delegate = endpoint.getChildEndpoint().createConsumer(processor);
                delegateService = null;
                if (delegate instanceof SuspendableService) {
                    delegateService = (SuspendableService) delegate;
                }
                ServiceHelper.startService(delegate);
            } catch (Exception e) {
                LOG.error("Failed to start master consumer for: " + endpoint + ". Reason: " + e, e);
            }
        }
    }

}
