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/*
 *  streams library
 *
 *  Copyright (C) 2011-2014 by Christian Bockermann, Hendrik Blom
 * 
 *  streams is a library, API and runtime environment for processing high
 *  volume data streams. It is composed of three submodules "stream-api",
 *  "stream-core" and "stream-runtime".
 *
 *  The streams library (and its submodules) is free software: you can 
 *  redistribute it and/or modify it under the terms of the 
 *  GNU Affero General Public License as published by the Free Software 
 *  Foundation, either version 3 of the License, or (at your option) any 
 *  later version.
 *
 *  The stream.ai library (and its submodules) is distributed in the hope
 *  that it will be useful, but WITHOUT ANY WARRANTY; without even the implied 
 *  warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU Affero General Public License for more details.
 *
 *  You should have received a copy of the GNU Affero General Public License
 *  along with this program.  If not, see http://www.gnu.org/licenses/.
 */
package stream.io;

import java.util.Collection;
import java.util.List;
import java.util.concurrent.CopyOnWriteArrayList;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import stream.Data;
import stream.data.DataFactory;

/**
 * 
 * A hub is simply a queue that dispatches incoming events to various listeners.
 * Listeners can dynamically register at a hub and unregister later on. The hub
 * will call the dataArrived method of each listener and provide a
 * copy of the data item.
 * 
 * 
 * The hub will not queue any events or keep them in memory. If data is enqueued
 * into the hub and no listener is registered, that data is simply discarded.
 * 
 * 
 * @author Christian Bockermann <[email protected]>
 * 
 */
public class Hub implements QueueService, HubService {

	static Logger log = LoggerFactory.getLogger(Hub.class);
	final List listener = new CopyOnWriteArrayList();

	String id;

	/**
	 * @see stream.service.Service#reset()
	 */
	@Override
	public void reset() throws Exception {
	}

	/**
	 * @see stream.io.QueueService#poll()
	 */
	@Override
	public Data poll() {
		return null;
	}

	/**
	 * @see stream.io.QueueService#take()
	 */
	@Override
	public Data take() {
		return null;
	}

	/**
	 * @see stream.io.QueueService#enqueue(stream.Data)
	 */
	@Override
	public boolean enqueue(Data item) {
		//
		// ENH: use a pool of dispatcher threads, which simultaneously
		// dispatch the items to more than one listener at once.
		//
		for (DataStreamListener dsl : listener) {
			try {
				dsl.dataArrived(DataFactory.create(item));
			} catch (Exception e) {
				e.printStackTrace();
			}
		}

		return true;
	}

	/**
	 * @see stream.io.HubService#register(stream.io.DataStreamListener)
	 */
	@Override
	public void register(DataStreamListener listener) throws Exception {
		this.listener.add(listener);
	}

	/**
	 * @see stream.io.HubService#unregister(stream.io.DataStreamListener)
	 */
	@Override
	public void unregister(DataStreamListener listener) throws Exception {
		this.listener.remove(listener);
	}

	/**
	 * @see stream.io.QueueService#level()
	 */
	@Override
	public int level() {
		return 0;
	}

	/**
	 * @see stream.io.QueueService#capacity()
	 */
	@Override
	public int capacity() {
		return 1;
	}

	/**
	 * @see stream.io.Sink#getId()
	 */
	@Override
	public String getId() {
		return id;
	}

	/**
	 * @see stream.io.Sink#setId(java.lang.String)
	 */
	@Override
	public void setId(String id) {
		this.id = id;
	}

	/**
	 * @see stream.io.Sink#write(stream.Data)
	 */
	@Override
	public boolean write(Data item) throws Exception {
		return this.enqueue(item);
	}

	@Override
	public void close() throws Exception {
		// TODO Auto-generated method stub

	}

	@Override
	public boolean write(Collection data) throws Exception {
		// TODO Auto-generated method stub
		return false;
	}

	/**
	 * @see stream.io.Sink#init()
	 */
	@Override
	public void init() throws Exception {
	}

	/**
	 * @see stream.io.Queue#getSize()
	 */
	@Override
	public Integer getSize() {
		return 0; // a hub is a queue of size 0
	}

	/**
	 * @see stream.io.Barrel#clear()
	 */
	@Override
	public int clear() {
		return 0;
	}

	/**
	 * @see stream.io.Source#read()
	 */
	@Override
	public Data read() throws Exception {
		return null;
	}

	@Override
	public void setCapacity(Integer limit) {
	}

	@Override
	public Integer getCapacity() {
		return 0;
	}
}