package org.daisy.pipeline.tts;
   
   import java.util.ArrayList;
   import java.util.Collection;
   import java.util.List;
   
   public class RoundRobinLoadBalancer implements LoadBalancer {
   	private int mIndex = 0;
   	private Object mSyncPoint;
  
  	private List<Host> mHosts;
  
  	/**
  	 * @param hostlist is the list of hosts. The first host will be considered
  	 *            as the master host.
  	 * @param syncPoint is used for locking when several threads attempt to call
  	 *            selectHost() with the same syncPoint.
  	 */
  	public RoundRobinLoadBalancer(String hostlist, Object syncPoint) {
  		mSyncPoint = syncPoint;
  		String[] parts = hostlist.split("[ ,;\t\n]+");
  		mHosts = new ArrayList<Host>();
  
  		for (int i = 0; i < parts.length; ++i) {
  			try {
  				Host h = new Host();
  				String[] pair = parts[i].split(":");
  				h.address = pair[0];
  				h.port = Integer.valueOf(pair[1]);
  				mHosts.add(h);
  			} catch (Exception e) {
  				throw new IllegalArgumentException("bad format for: '" + parts[i] + "'");
  			}
  		}
  
  	}
  
  	@Override
  	public Host selectHost() {
  		int index;
  		if (mSyncPoint != null) {
  			synchronized (mSyncPoint) {
  				mIndex = (mIndex + 1) % mHosts.size();
  				index = mIndex;
  			}
  		} else {
  			mIndex = (mIndex + 1) % mHosts.size();
  			index = mIndex;
  		}
  
  		return mHosts.get(index);
  	}
  
  	@Override
  	public Collection<Host> getAllHosts() {
  		return mHosts;
  	}
  
  	@Override
  	public Host getMaster() {
  		return mHosts.get(0);
  	}
  
  	@Override
  	public void discard(Host h) {
  		mHosts.remove(h);
  	}
  
  	public void discardAll(Collection<Host> hosts) {
  		mHosts.removeAll(hosts);
  	}
  
  }