package org.litesoft.GWT.eventbus.client.nonpublic;

import java.util.*;

import org.litesoft.GWT.eventbus.client.*;

public class SubscriptionManager
{
    private Map mSubscribers = new HashMap(); // TargetName to ListenersEntry
    private String mEBform;

    public SubscriptionManager( String pEBform )
    {
        mEBform = pEBform;
    }

    public synchronized void clear()
    {
        mSubscribers.clear();
    }

    public synchronized boolean anySubscribers( String pTargetName )
    {
        return (null != getListenersEntry( pTargetName ));
    }

    public synchronized boolean hasPeerAcknowledged( String pTargetName )
    {
        ListenersEntry entry = getListenersEntry( pTargetName );
        return (entry != null) && entry.hasPeerAcknowledged();
    }

    public synchronized void setPeerAcknowledged( String pTargetName )
    {
        ListenersEntry entry = getListenersEntry( pTargetName );
        if ( entry != null )
        {
            entry.setPeerAcknowledged();
        }
    }

    public synchronized EventPackageListener[] getListenersFor( String pTargetName )
    {
        ListenersEntry entry = getListenersEntry( pTargetName );
        return (entry != null) ? entry.getListeners() : null;
    }

    private ListenersEntry getListenersEntry( String pTargetName )
    {
        return (ListenersEntry) mSubscribers.get( pTargetName );
    }

    /**
     * @return T/F if added first pListener for pTargetName
     */
    public synchronized boolean subscribe( String pTargetName, EventPackageListener pListener )
    {
        ListenersEntry entry = getListenersEntry( pTargetName );
        if ( entry == null )
        {
            mSubscribers.put( pTargetName, new ListenersEntry( pListener ) );
            return true; // Just Added first Listener for TargetName
        }
        entry.add( pListener );
        return false; // did NOT just add first one!
    }

    /**
     * @return T/F if removed last pListener for pTargetName
     */
    public synchronized boolean unsubscribe( String pTargetName, EventPackageListener pListener )
    {
        ListenersEntry entry = getListenersEntry( pTargetName );
        if ( entry != null )
        {
            if ( entry.remove( pListener ) )
            {
                mSubscribers.remove( pTargetName );
                return true; // reduced to nothing
            }
        }
        return false;
    }

    public String toString()
    {
        return mEBform;
    }

    private static class ListenersEntry
    {
        private EventPackageListener[] mListeners;
        private boolean mPeerAcknowledged = false;

        public ListenersEntry( EventPackageListener pListener )
        {
            mListeners = new EventPackageListener[]{pListener};
        }

        public EventPackageListener[] getListeners()
        {
            return mListeners;
        }

        public boolean hasPeerAcknowledged()
        {
            return mPeerAcknowledged;
        }

        public void setPeerAcknowledged()
        {
            mPeerAcknowledged = true;
        }

        /**
         * @return T/F if pListener added (not already in the list)
         */
        public boolean add( EventPackageListener pListener )
        {
            EventPackageListener[] newListeners = new EventPackageListener[mListeners.length + 1];
            int i = 0;
            for ( ; i < mListeners.length; i++ )
            {
                if ( pListener == (newListeners[i] = mListeners[i]) )
                {
                    return false;
                }
            }
            newListeners[i] = pListener;
            mListeners = newListeners;
            return true;
        }

        /**
         * @return T/F if would have reduced to NO listeners
         */
        public boolean remove( EventPackageListener pListener )
        {
            int at = -1;
            for ( int i = 0; i < mListeners.length; i++ )
            {
                if ( pListener == mListeners[i] )
                {
                    at = i;
                    break;
                }
            }
            if ( at == -1 )
            {
                return false;
            }
            if ( mListeners.length == 1 )
            {
                return true; // reduced to nothing
            }
            EventPackageListener[] newListeners = new EventPackageListener[mListeners.length - 1];
            int from = 0, to = 0;
            while ( from < at )
            {
                newListeners[to++] = mListeners[from++];
            }
            from++;
            while ( from < mListeners.length )
            {
                newListeners[to++] = mListeners[from++];
            }
            mListeners = newListeners;
            return false;
        }
    }
}