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/*
 ===========================================================================
 Copyright (c) 2010 BrickRed Technologies Limited

 Permission is hereby granted, free of charge, to any person obtaining a copy
 of this software and associated documentation files (the "Software"), to deal
 in the Software without restriction, including without limitation the rights
 to use, copy, modify, merge, publish, distribute, sub-license, and/or sell
 copies of the Software, and to permit persons to whom the Software is
 furnished to do so, subject to the following conditions:

 The above copyright notice and this permission notice shall be included in
 all copies or substantial portions of the Software.

 THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 THE SOFTWARE.
 ===========================================================================

 */

package org.brickred.socialauth.util;

import java.io.File;
import java.io.InputStream;
import java.io.StringWriter;

import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.ParserConfigurationException;
import javax.xml.transform.Transformer;
import javax.xml.transform.TransformerException;
import javax.xml.transform.TransformerFactory;
import javax.xml.transform.dom.DOMSource;
import javax.xml.transform.stream.StreamResult;

import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.Node;
import org.w3c.dom.NodeList;

/**
 * This is a utility class, which is used to read the xml files.
 * 
 * @author Tarun Nagpal
 */
public class XMLParseUtil {

	/**
	 * Static helper function to get the element data of the specified node.
	 * 
	 * @param node
	 *            the node where the text data resides; may be null
	 *            in which case this funtion will return ""
	 * 
	 * @return the complete text of the specified node, or an empty string if
	 *         the node has no text or is null
	 */
	public static String getElementData(final Node node) {
		StringBuffer ret = new StringBuffer();

		if (node != null) {
			Node text;
			for (text = node.getFirstChild(); text != null; text = text
					.getNextSibling()) {
				/**
				 * the item's value is in one or more text nodes which are its
				 * immediate children
				 */
				if (text.getNodeType() == Node.TEXT_NODE
						|| text.getNodeType() == Node.CDATA_SECTION_NODE) {
					ret.append(text.getNodeValue());
				} else {
					if (text.getNodeType() == Node.ENTITY_REFERENCE_NODE) {
						ret.append(getElementData(text));
					}
				}
			}
		}
		return ret.toString();
	}

	/**
	 * Gets the text value of the specified element.
	 * 
	 * @param root
	 *            the root of the element whose text is to be retrieved; assumed
	 *            not to be null.
	 * @param elementName
	 *            the name of the element whose text is to be retrieved.
	 * 
	 * @return the retrieved text value of the specified element or null if root
	 *         has no given element.
	 */
	public static String getElementData(final Element root,
			final String elementName) {
		NodeList nodes = root.getElementsByTagName(elementName);
		if (nodes.getLength() < 1) {
			return null;
		}

		return getElementData(nodes.item(0));
	}

	/**
	 * Loads the xml file into an xml document and returns the root element.
	 * 
	 * @param fileName
	 *            the fully qualified name of the XML file to load; assumed not
	 *            to be null.
	 * 
	 * @return root element of the xml document, never null.
	 * 
	 * @throws Exception
	 *             on any error
	 */
	public static Element loadXmlResource(final String fileName)
			throws Exception {
		File file = new File(fileName);
		DocumentBuilder db = getDocumentBuilder();
		Document doc = db.parse(file);
		return doc.getDocumentElement();
	}

	/**
	 * Loads the imput stream and returns the root element.
	 * 
	 * @param in
	 *            Input Stream.
	 * 
	 * @return root element of the xml document, never null.
	 * 
	 * @throws Exception
	 *             on any error
	 */
	public static Element loadXmlResource(final InputStream in)
			throws Exception {
		DocumentBuilder db = getDocumentBuilder();
		Document doc = db.parse(in);
		return doc.getDocumentElement();
	}

	/**
	 * Returns a DocumentBuilder, which is used for parsing XML
	 * documents.
	 * 
	 * @return a DocumentBuilder which is used for parsing XML
	 *         documents. Never null.
	 */
	public static DocumentBuilder getDocumentBuilder() {
		try {
			DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
			dbf.setNamespaceAware(true);
			dbf.setValidating(false);

			return dbf.newDocumentBuilder();
		} catch (ParserConfigurationException e) {
			e.printStackTrace();
			throw new RuntimeException(e.getMessage());
		}
	}

	public static String getStringFromElement(Element doc)
			throws TransformerException {

		DOMSource domSource = new DOMSource(doc);
		StringWriter writer = new StringWriter();
		StreamResult result = new StreamResult(writer);
		TransformerFactory tf = TransformerFactory.newInstance();
		Transformer transformer = tf.newTransformer();
		// transformer.setOutputProperty(OutputKeys.ENCODING, "UTF-8");
		// transformer.setOutputProperty(OutputKeys.INDENT, "yes");
		transformer.transform(domSource, result);
		writer.flush();
		return writer.toString();
	}
}