/**
 * Licensed to Apereo under one or more contributor license
 * agreements. See the NOTICE file distributed with this work
 * for additional information regarding copyright ownership.
 * Apereo licenses this file to you 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 the following location:
 *
 *   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.jasig.portal.character.stream;

import java.util.NoSuchElementException;

import org.jasig.portal.character.stream.events.CharacterEvent;

/**
 * Base class for application event readers that simply want to filter
 * or monitor events passing through the reader.
 * 
 * @author Eric Dalquist
 * @version $Revision$
 */
public abstract class FilteringCharacterEventReader extends CharacterEventReaderDelegate {
    private CharacterEvent peekedEvent = null;
    
    public FilteringCharacterEventReader(CharacterEventReader delegate) {
        super(delegate);
    }
    
    @Override
    public boolean hasNext() {
        try {
            return peekedEvent != null || (super.hasNext() && this.peek() != null);
        }
        catch (NoSuchElementException e) {
            return false;
        }
    }
    
    @Override
    public CharacterEvent next() {
        return internalNext(false);
    }

    @Override
    public CharacterEvent peek() {
        if (peekedEvent != null) {
            return peekedEvent;
        }
        
        peekedEvent = internalNext(true);
        return peekedEvent;
    }

    protected final CharacterEvent internalNext(boolean peek) {
        CharacterEvent event = null;
        
        if (peekedEvent != null) {
            event = peekedEvent;
            peekedEvent = null;
            return event;
        }
        
        do {
            event = super.next();
            event = this.filterEvent(event, peek);
        } while (event == null);
        
        return event;
    }
    
    /**
     * @param event The current event
     * @param peek If the event is from a {@link #peek()} call
     * @return The event to return, if null is returned the event is dropped from the stream and the next event will be used.
     */
    protected abstract CharacterEvent filterEvent(CharacterEvent event, boolean peek);
}
