// Copyright 2006 Google Inc.
// All Rights Reserved
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions
// are met:
// 
//  * Redistributions of source code must retain the above copyright
//    notice, this list of conditions and the following disclaimer.
//  * Redistributions in binary form must reproduce the above copyright
//    notice, this list of conditions and the following disclaimer in
//    the documentation and/or other materials provided with the
//    distribution.
// 
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
// FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
// COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
// INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
// BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
// LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
// CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
// LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
// ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
// POSSIBILITY OF SUCH DAMAGE. 

/**
 * @fileoverview
 * XML utilities.
 *
 */

goog.provide('goog.dom.xml');

goog.require('goog.dom');


/**
 * Max XML size for MSXML2.  Used to prevent potential DoS attacks.
 * @type {number}
 */
goog.dom.xml.MAX_XML_SIZE_KB = 2 * 1024;  // In kB


/**
 * Max XML size for MSXML2.  Used to prevent potential DoS attacks.
 * @type {number}
 */
goog.dom.xml.MAX_ELEMENT_DEPTH = 256; // Same default as MSXML6.


/**
 * Creates an XML document appropriate for the current JS runtime
 * @param {string} opt_rootTagName The root tag name.
 * @param {string} opt_namespaceUri Namespace URI of the document element.
 * @return {Document} The new document.
 */
goog.dom.xml.createDocument = function(opt_rootTagName, opt_namespaceUri) {
  if (opt_namespaceUri && !opt_rootTagName) {
    throw Error("Can't create document with namespace and no root tag");
  }
  if (document.implementation && document.implementation.createDocument) {
    return document.implementation.createDocument(opt_namespaceUri || '',
                                                  opt_rootTagName || '',
                                                  null)
  } else if (typeof ActiveXObject != 'undefined') {
    var doc = goog.dom.xml.createMsXmlDocument_();
    if (doc) {
      if (opt_rootTagName) {
        doc.appendChild(doc.createNode(goog.dom.NodeType.ELEMENT,
                                       opt_rootTagName,
                                       opt_namespaceUri || ''));
      }
      return doc;
    }
  }
  throw Error('Your browser does not support creating new documents');
};


/**
 * Creates an XML document from a string
 * @param {string} xml The text.
 * @return {Document} XML document from the text.
 */
goog.dom.xml.loadXml = function(xml) {
  if (typeof DOMParser != 'undefined') {
    return new DOMParser().parseFromString(xml, 'application/xml');
  } else if (typeof ActiveXObject != 'undefined') {
    var doc = goog.dom.xml.createMsXmlDocument_();
    doc.loadXML(xml);
    return doc;
  }
  throw Error('Your browser does not support loading xml documents');
};


/**
 * Serializes an XML document or subtree to string.
 * @param {Document|Element} xml The document or the root node of the subtree.
 * @return {string} The serialized XML.
 */
goog.dom.xml.serialize = function(xml) {
  // Compatible with Firefox, Opera and WebKit.
  if (typeof XMLSerializer != 'undefined') {
    return new XMLSerializer().serializeToString(xml);
  }
  // Compatible with Internet Explorer.
  var text = xml.xml;
  if (text) {
    return text;
  }
  throw Error('Your browser does not support serializing XML documents');
};


/**
 * Selects a single node using an Xpath expression and a root node
 * @param {Node} node The root node.
 * @param {string} path Xpath selector.
 * @return {Node?} The selected node, or null if no matching node.
 */
goog.dom.xml.selectSingleNode = function(node, path) {
  if (typeof node.selectSingleNode != 'undefined') {
    var doc = goog.dom.getOwnerDocument(node);
    if (typeof doc.setProperty != 'undefined') {
      doc.setProperty('SelectionLanguage', 'XPath');
    }
    return node.selectSingleNode(path);
  } else if (document.implementation.hasFeature('XPath', '3.0')) {
    var doc = goog.dom.getOwnerDocument(node);
    var resolver = doc.createNSResolver(doc.documentElement);
    var result = doc.evaluate(path, node, resolver,
        XPathResult.FIRST_ORDERED_NODE_TYPE, null);
    return result.singleNodeValue;
  }
  return null;
};


/**
 * Selects multiple nodes using an Xpath expression and a root node
 * @param {Node} node The root node.
 * @param {string} path Xpath selector.
 * @return {(NodeList,Array.<Node>)} The selected nodes, or empty array if no
 *     matching nodes.
 */
goog.dom.xml.selectNodes = function(node, path) {
  if (typeof node.selectNodes != 'undefined') {
    var doc = goog.dom.getOwnerDocument(node);
    if (typeof doc.setProperty != 'undefined') {
      doc.setProperty('SelectionLanguage', 'XPath');
    }
    return node.selectNodes(path);
  } else if (document.implementation.hasFeature('XPath', '3.0')) {
    var doc = goog.dom.getOwnerDocument(node);
    var resolver = doc.createNSResolver(doc.documentElement);
    var nodes = doc.evaluate(path, node, resolver,
        XPathResult.ORDERED_NODE_SNAPSHOT_TYPE, null);
    var results = [];
    var count = nodes.snapshotLength;
    for (var i = 0; i < count; i++) {
      results.push(nodes.snapshotItem(i));
    }
    return results;
  } else {
   return [];
  }
};


/**
 * Creates an instance of the MSXML2.DOMDocument.
 * @return {Document} The new document.
 * @private
 */
goog.dom.xml.createMsXmlDocument_ = function() {
  var doc = new ActiveXObject('MSXML2.DOMDocument');
  if (doc) {
    // Prevent potential vulnerabilities exposed by MSXML2, see
    // http://b/1707300 and http://wiki/Main/ISETeamXMLAttacks for details.
    doc.resolveExternals = false;
    doc.validateOnParse = false;
    doc.setProperty('ProhibitDTD', true);
    doc.setProperty('MaxXMLSize', goog.dom.xml.MAX_XML_SIZE_KB);
    doc.setProperty('MaxElementDepth', goog.dom.xml.MAX_ELEMENT_DEPTH);
  }
  return doc;
};