/*--

 * Copyright 2010 René M. de Bloois

 *

 * Licensed 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

 *

 *     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 solidstack.xml.elements;



import javax.xml.stream.XMLStreamConstants;

import javax.xml.stream.XMLStreamException;

import javax.xml.stream.XMLStreamReader;



import solidstack.lang.Assert;

import solidstack.lang.SystemException;





/**

 * Reads an element from an {@link XMLStreamReader}.

 *

 * @author René M. de Bloois

 */

@SuppressWarnings( "restriction" )

public class StaxNodeReader

{

	/**

	 * This utility class cannot be constructed.

	 */

	private StaxNodeReader()

	{

		super();

	}



	/**

	 * Reads a element from the given {@link XMLStreamReader}.

	 *

	 * @param reader The {@link XMLStreamReader} to read a node from.

	 * @return The element that is read.

	 * @throws XMLStreamException When thrown by the {@link XMLStreamReader}.

	 */

	static public Element readNode( XMLStreamReader reader ) throws XMLStreamException

	{

		int event = reader.getEventType();

		Assert.isTrue( event == XMLStreamConstants.START_ELEMENT, "Expecting an element start" );



		Element element = new Element( reader.getLocalName(), null );

		read( reader, element );

		return element;

	}



	/**

	 * A recursive method to read elements from the {@link XMLStreamReader}.

	 *

	 * @param reader The {@link XMLStreamReader} to read a node from.

	 * @param element The element to populate with attributes and children.

	 * @throws XMLStreamException When thrown by the {@link XMLStreamReader}.

	 */

	static protected void read( XMLStreamReader reader, Element element ) throws XMLStreamException

	{

		for( int i = 0; i < reader.getAttributeCount(); i++ )

			element.addAttribute( reader.getAttributeLocalName( i ), reader.getAttributeValue( i ) );



		StringBuilder buffer = new StringBuilder();



		while( reader.hasNext() )

		{

			int event = reader.next();

			if( event == XMLStreamConstants.CHARACTERS )

			{

				if( !reader.isWhiteSpace() )

					buffer.append( reader.getText() );

			}

			else if( event == XMLStreamConstants.START_ELEMENT )

			{

				if( buffer.length() > 0 )

				{

					element.addText( buffer.toString() );

					buffer.setLength( 0 );

				}



				Element child = new Element( reader.getLocalName(), element );

				element.addChild( child );



				read( reader, child );

			}

			else if( event == XMLStreamConstants.END_ELEMENT )

			{

				if( buffer.length() > 0 )

				{

					element.addText( buffer.toString() );

					buffer.setLength( 0 );

				}

				return;

			}

			else if( event == XMLStreamConstants.COMMENT )

			{

				// Ignore comments

			}

			else

				throw new SystemException( "Unexpected event [" + event + "]" );

		}

	}

}