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/*
* Conditions Of Use 
* 
* This software was developed by employees of the National Institute of
* Standards and Technology (NIST), an agency of the Federal Government.
* Pursuant to title 15 Untied States Code Section 105, works of NIST
* employees are not subject to copyright protection in the United States
* and are considered to be in the public domain.  As a result, a formal
* license is not needed to use the software.
* 
* This software is provided by NIST as a service and is expressly
* provided "AS IS."  NIST MAKES NO WARRANTY OF ANY KIND, EXPRESS, IMPLIED
* OR STATUTORY, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTY OF
* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE, NON-INFRINGEMENT
* AND DATA ACCURACY.  NIST does not warrant or make any representations
* regarding the use of the software or the results thereof, including but
* not limited to the correctness, accuracy, reliability or usefulness of
* the software.
* 
* Permission to use this software is contingent upon your acceptance
* of the terms of this agreement
*  
* .
* 
*/
package gov.nist.javax.sip.message;

import gov.nist.javax.sip.header.*;
import java.util.ListIterator;
import java.util.NoSuchElementException;

/**
 * Iterator over lists of headers. Allows for uniform removal handling for singleton headers.
 * @author M. Ranganathan
 * @version 1.2 $Revision: 1.7 $ $Date: 2006/07/13 09:02:48 $
 * @since 1.1
 */
public class HeaderIterator implements ListIterator {
	private boolean toRemove;
	private int index;
	private SIPMessage sipMessage;
	private SIPHeader sipHeader;

	protected HeaderIterator(SIPMessage sipMessage, SIPHeader sipHeader) {
		this.sipMessage = sipMessage;
		this.sipHeader = sipHeader;
	}

	public Object next() throws NoSuchElementException {
		if (sipHeader == null || index == 1)
			throw new NoSuchElementException();
		toRemove = true;
		index = 1;
		return (Object) sipHeader;
	}

	public Object previous() throws NoSuchElementException {
		if (sipHeader == null || index == 0)
			throw new NoSuchElementException();
		toRemove = true;
		index = 0;
		return (Object) sipHeader;
	}

	public int nextIndex() {
		return 1;
	}

	public int previousIndex() {
		return index == 0 ? -1 : 0;
	}

	public void set(Object header) {
		throw new UnsupportedOperationException();
	}

	public void add(Object header) {
		throw new UnsupportedOperationException();
	}

	public void remove() throws IllegalStateException {
		if (this.sipHeader == null)
			throw new IllegalStateException();
		if (toRemove) {
			this.sipHeader = null;
			this.sipMessage.removeHeader(sipHeader.getName());
		} else {
			throw new IllegalStateException();
		}
	}

	public boolean hasNext() {
		return index == 0;
	}

	public boolean hasPrevious() {
		return index == 1;
	}
}