/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this file,
 * You can obtain one at http://mozilla.org/MPL/2.0/. */

/** Helper functions for parsing and serializing XML */

Components.utils.import("resource://calendar/modules/calUtils.jsm");

this.EXPORTED_SYMBOLS = ["cal"];
cal.xml = {} || cal.xml;

/**
 * Evaluate an XPath query for the given node. Be careful with the return value
 * here, as it may be:
 *
 * - null, if there are no results
 * - a number, string or boolean value
 * - an array of strings or DOM elements
 *
 * @param aNode     The context node to search from
 * @param aExpr     The XPath expression to search for
 * @param aResolver (optional) The namespace resolver to use for the expression
 * @param aType     (optional) Force a result type, must be an XPathResult constant
 * @return          The result, see above for details.
 */
cal.xml.evalXPath = function evaluateXPath(aNode, aExpr, aResolver, aType) {
    const XPR = Components.interfaces.nsIDOMXPathResult;
    let doc = (aNode.ownerDocument ? aNode.ownerDocument : aNode);
    let resolver = aResolver || doc.createNSResolver(doc.documentElement);
    let resultType = aType || XPR.ANY_TYPE;

    let result = doc.evaluate(aExpr, aNode, resolver, resultType, null);
    let returnResult, next;
    switch (result.resultType) {
        case XPR.NUMBER_TYPE:
            returnResult = result.numberValue;
            break;
        case XPR.STRING_TYPE:
            returnResult = result.stringValue;
            break;
        case XPR.BOOLEAN_TYPE:
            returnResult = result.booleanValue;
            break;
        case XPR.UNORDERED_NODE_ITERATOR_TYPE:
        case XPR.ORDERED_NODE_ITERATOR_TYPE:
            returnResult = [];
            while ((next = result.iterateNext())) {
                if (next instanceof Components.interfaces.nsIDOMText) {
                    returnResult.push(next.wholeText);
                } else if (next instanceof Components.interfaces.nsIDOMAttr) {
                    returnResult.push(next.value);
                } else {
                    returnResult.push(next);
                }
            }
            break;
        case XPR.UNORDERED_NODE_SNAPSHOT_TYPE:
        case XPR.ORDERED_NODE_SNAPSHOT_TYPE:
            returnResult = [];
            for (let i = 0; i < result.snapshotLength; i++) {
                next = result.snapshotItem(i);
                if (next instanceof Components.interfaces.nsIDOMText) {
                    returnResult.push(next.wholeText);
                } else if (next instanceof Components.interfaces.nsIDOMAttr) {
                    returnResult.push(next.value);
                } else {
                    returnResult.push(next);
                }
            }
            break;
        case XPR.ANY_UNORDERED_NODE_TYPE:
        case XPR.FIRST_ORDERED_NODE_TYPE:
            returnResult = result.singleNodeValue;
            break;
        default:
            returnResult = null;
            break;
    }

    if (Array.isArray(returnResult) && returnResult.length == 0) {
        returnResult = null;
    }

    return returnResult;
};

/**
 * Convenience function to evaluate an XPath expression and return null or the
 * first result. Helpful if you just expect one value in a text() expression,
 * but its possible that there will be more than one. The result may be:
 *
 * - null, if there are no results
 * - A string, number, boolean or DOM Element value
 *
 * @param aNode     The context node to search from
 * @param aExpr     The XPath expression to search for
 * @param aResolver (optional) The namespace resolver to use for the expression
 * @param aType     (optional) Force a result type, must be an XPathResult constant
 * @return          The result, see above for details.
 */
cal.xml.evalXPathFirst = function evalXPathFirst(aNode, aExpr, aResolver, aType) {
    let result = cal.xml.evalXPath(aNode, aExpr, aResolver, aType);

    if (Array.isArray(result)) {
        return result[0];
    } else {
        return result;
    }
};

/**
 * Parse the given string into a DOM tree
 *
 * @param str       The string to parse
 * @param docUri    (optional) The document URI to use
 * @param baseUri   (optional) The base URI to use
 * @return          The parsed DOM Document
 */
cal.xml.parseString = function(str, docUri, baseUri) {
    let parser = Components.classes["@mozilla.org/xmlextras/domparser;1"]
                           .createInstance(Components.interfaces.nsIDOMParser);

    parser.init(null, docUri, baseUri);
    return parser.parseFromString(str, "application/xml");
};

/**
 * Read an XML file synchronously. This method should be avoided, consider
 * rewriting the caller to be asynchronous.
 *
 * @param uri       The URI to read.
 * @return          The DOM Document resulting from the file.
 */
cal.xml.parseFile = function(uri) {
    let req = Components.classes["@mozilla.org/xmlextras/xmlhttprequest;1"]
                        .createInstance(Components.interfaces.nsIXMLHttpRequest);

    req.open('GET', uri, false);
    req.overrideMimeType("text/xml");
    req.send(null);
    return req.responseXML;
};

/**
 * Serialize the DOM tree into a string.
 *
 * @param doc       The DOM document to serialize
 * @return          The DOM document as a string.
 */
cal.xml.serializeDOM = function(doc) {
    let serializer = Components.classes["@mozilla.org/xmlextras/xmlserializer;1"]
                               .createInstance(Components.interfaces.nsIDOMSerializer);
    return serializer.serializeToString(doc);
};

/**
 * Escape a string for use in XML
 *
 * @param str           The string to escape
 * @param isAttribute   If true, " and ' are also escaped
 * @return              The escaped string
 */
cal.xml.escapeString = function escapeString(str, isAttribute) {
    return str.replace(/[&<>'"]/g, function(chr) {
        switch (chr) {
            case "&": return "&amp;";
            case "<": return "&lt;";
            case ">": return "&gt;";
            case '"': if (isAttribute) return "&quot;";
            case "'": if (isAttribute) return "&apos;";
            default: return chr;
        }
    });
};
