/*
 * Hibernate, Relational Persistence for Idiomatic Java
 *
 * Copyright (c) 2013, Red Hat Inc. or third-party contributors as
 * indicated by the @author tags or express copyright attribution
 * statements applied by the authors.  All third-party contributions are
 * distributed under license by Red Hat Inc.
 *
 * This copyrighted material is made available to anyone wishing to use, modify,
 * copy, or redistribute it subject to the terms and conditions of the GNU
 * Lesser General Public License, as published by the Free Software Foundation.
 *
 * This program 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 Lesser General Public License
 * for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with this distribution; if not, write to:
 * Free Software Foundation, Inc.
 * 51 Franklin Street, Fifth Floor
 * Boston, MA  02110-1301  USA
 */
package org.hibernate.internal.util.xml;

import javax.xml.stream.XMLEventReader;
import javax.xml.stream.XMLStreamConstants;
import javax.xml.stream.XMLStreamException;
import javax.xml.stream.events.Characters;
import javax.xml.stream.events.EntityDeclaration;
import javax.xml.stream.events.EntityReference;
import javax.xml.stream.events.XMLEvent;
import javax.xml.stream.util.EventReaderDelegate;

Base for XMLEventReader that implements the getElementText() and nextTag() APIs in a way that is agnostic from the rest of the XMLEventReader implementation. Both will use the subclasses internalNextEvent() as the exclusive way to read events. Note, copied from the uPortal project by permission of author. See https://github.com/Jasig/uPortal/blob/master/uportal-war/src/main/java/org/jasig/portal/xml/stream/BaseXMLEventReader.java 
Author:
Eric Dalquist/**
 * Base for XMLEventReader that implements the {@link #getElementText()} and {@link #nextTag()} APIs in a
 * way that is agnostic from the rest of the XMLEventReader implementation. Both will use the subclasses
 * {@link #internalNextEvent()} as the exclusive way to read events.
 *
 * Note, copied from the uPortal project by permission of author.  See
 * https://github.com/Jasig/uPortal/blob/master/uportal-war/src/main/java/org/jasig/portal/xml/stream/BaseXMLEventReader.java
 *
 * @author Eric Dalquist
 */
public abstract class BaseXMLEventReader extends EventReaderDelegate {
	private XMLEvent previousEvent;

	public BaseXMLEventReader(XMLEventReader reader) {
		super(reader);
	}

	
Subclass's version of nextEvent(), called by next() /**
	 * Subclass's version of {@link #nextEvent()}, called by {@link #next()}
	 */
	protected abstract XMLEvent internalNextEvent() throws XMLStreamException;

	
Returns:
The XMLEvent returned by the last call to internalNextEvent()/**
	 * @return The XMLEvent returned by the last call to {@link #internalNextEvent()}
	 */
	protected final XMLEvent getPreviousEvent() {
		return this.previousEvent;
	}

	@Override
	public final XMLEvent nextEvent() throws XMLStreamException {
		this.previousEvent = this.internalNextEvent();
		return this.previousEvent;
	}

	/* (non-Javadoc)
	 * @see java.util.Iterator#next()
	 */
	@Override
	public final Object next() {
		try {
			return this.nextEvent();
		}
		catch (XMLStreamException e) {
			return null;
		}
	}

	/* (non-Javadoc)
	 * @see javax.xml.stream.XMLEventReader#getElementText()
	 */
	@Override
	public final String getElementText() throws XMLStreamException {
		XMLEvent event = this.previousEvent;
		if (event == null) {
			throw new XMLStreamException("Must be on START_ELEMENT to read next text, element was null");
		}
		if (!event.isStartElement()) {
			throw new XMLStreamException("Must be on START_ELEMENT to read next text", event.getLocation());
		}

		final StringBuilder text = new StringBuilder();
		while (!event.isEndDocument()) {
			switch (event.getEventType()) {
				case XMLStreamConstants.CHARACTERS:
				case XMLStreamConstants.SPACE:
				case XMLStreamConstants.CDATA: {
					final Characters characters = event.asCharacters();
					text.append(characters.getData());
					break;
				}
				case XMLStreamConstants.ENTITY_REFERENCE: {
					final EntityReference entityReference = (EntityReference)event;
					final EntityDeclaration declaration = entityReference.getDeclaration();
					text.append(declaration.getReplacementText());
					break;
				}
				case XMLStreamConstants.COMMENT:
				case XMLStreamConstants.PROCESSING_INSTRUCTION: {
					//Ignore
					break;
				}
				default: {
					throw new XMLStreamException("Unexpected event type '" + XMLStreamConstantsUtils.getEventName(event.getEventType()) + "' encountered. Found event: " + event, event.getLocation());
				}
			}

			event = this.nextEvent();
		}

		return text.toString();
	}

	/* (non-Javadoc)
	 * @see javax.xml.stream.XMLEventReader#nextTag()
	 */
	@Override
	public final XMLEvent nextTag() throws XMLStreamException {
		XMLEvent event = this.nextEvent();
		while ((event.isCharacters() && event.asCharacters().isWhiteSpace())
				|| event.isProcessingInstruction()
				|| event.getEventType() == XMLStreamConstants.COMMENT) {

			event = this.nextEvent();
		}

		if (!event.isStartElement()  && event.isEndElement()) {
			throw new XMLStreamException("Unexpected event type '" + XMLStreamConstantsUtils.getEventName(event.getEventType()) + "' encountered. Found event: " + event, event.getLocation());
		}

		return event;
	}
}