/*

Copyright (c) 2009, Yahoo! Inc. All rights reserved.

Code licensed under the BSD License:

http://developer.yahoo.net/yui/license.txt

version: 3.0.0b1

build: 1163

*/

YUI.add('json-parse', function(Y) {

/**

 * <p>The JSON module adds support for serializing JavaScript objects into

 * JSON strings and parsing JavaScript objects from strings in JSON format.</p>

 *

 * <p>The JSON namespace is added to your YUI instance including static methods

 * Y.JSON.parse(..) and Y.JSON.stringify(..).</p>

 *

 * <p>The functionality and method signatures follow the ECMAScript 5

 * specification.  In browsers with native JSON support, the native

 * implementation is used.</p>

 *

 * <p>The <code>json</code> module is a rollup of <code>json-parse</code> and

 * <code>json-stringify</code>.</p>

 * 

 * <p>As their names suggest, <code>json-parse</code> adds support for parsing

 * JSON data (Y.JSON.parse) and <code>json-stringify</code> for serializing

 * JavaScript data into JSON strings (Y.JSON.stringify).  You may choose to

 * include either of the submodules individually if you don't need the

 * complementary functionality, or include the rollup for both.</p>

 *

 * @module json

 * @class JSON

 * @static

 */

/**

 * Provides Y.JSON.parse method to accept JSON strings and return native

 * JavaScript objects.

 *

 * @module json

 * @submodule json-parse

 * @for JSON

 * @static

 */

// All internals kept private for security reasons

    /**

     * Alias to native browser implementation of the JSON object if available.

     *

     * @property Native

     * @type {Object}

     * @private

     */

var Native = Y.config.win.JSON,

    /**

     * Replace certain Unicode characters that JavaScript may handle incorrectly

     * during eval--either by deleting them or treating them as line

     * endings--with escape sequences.

     * IMPORTANT NOTE: This regex will be used to modify the input if a match is

     * found.

     *

     * @property _UNICODE_EXCEPTIONS

     * @type {RegExp}

     * @private

     */

    _UNICODE_EXCEPTIONS = /[\u0000\u00ad\u0600-\u0604\u070f\u17b4\u17b5\u200c-\u200f\u2028-\u202f\u2060-\u206f\ufeff\ufff0-\uffff]/g,

    /**

     * First step in the safety evaluation.  Regex used to replace all escape

     * sequences (i.e. "\\", etc) with '@' characters (a non-JSON character).

     *

     * @property _ESCAPES

     * @type {RegExp}

     * @private

     */

    _ESCAPES = /\\(?:["\\\/bfnrt]|u[0-9a-fA-F]{4})/g,

    /**

     * Second step in the safety evaluation.  Regex used to replace all simple

     * values with ']' characters.

     *

     * @property _VALUES

     * @type {RegExp}

     * @private

     */

    _VALUES  = /"[^"\\\n\r]*"|true|false|null|-?\d+(?:\.\d*)?(?:[eE][+\-]?\d+)?/g,

    /**

     * Third step in the safety evaluation.  Regex used to remove all open

     * square brackets following a colon, comma, or at the beginning of the

     * string.

     *

     * @property _BRACKETS

     * @type {RegExp}

     * @private

     */

    _BRACKETS = /(?:^|:|,)(?:\s*\[)+/g,

    /**

     * Final step in the safety evaluation.  Regex used to test the string left

     * after all previous replacements for invalid characters.

     *

     * @property _INVALID

     * @type {RegExp}

     * @private

     */

    _INVALID = /[^\],:{}\s]/,

    /**

     * Test for JSON string of simple data string, number, boolean, or null.

     * E.g. '"some string"', "true", "false", "null", or numbers "-123e+7"

     * This was needed for some WIP native implementations (FF3.1b2) but may be

     * unnecessary now.

     *

     * @property _SIMPLE

     * @type {RegExp}

     * @private

     */

    _SIMPLE = /^\s*(?:"[^"\\\n\r]*"|true|false|null|-?\d+(?:\.\d*)?(?:[eE][+\-]?\d+)?)\s*$/,

    /**

     * Replaces specific unicode characters with their appropriate \unnnn

     * format. Some browsers ignore certain characters during eval.

     *

     * @method escapeException

     * @param c {String} Unicode character

     * @return {String} the \unnnn escapement of the character

     * @private

     */

    _escapeException = function (c) {

        return '\\u'+('0000'+(+(c.charCodeAt(0))).toString(16)).slice(-4);

    },

    /**

     * Traverses nested objects, applying a reviver function to each (key,value)

     * from the scope if the key:value's containing object.  The value returned

     * from the function will replace the original value in the key:value pair.

     * If the value returned is undefined, the key will be omitted from the

     * returned object.

     *

     * @method _revive

     * @param data {MIXED} Any JavaScript data

     * @param reviver {Function} filter or mutation function

     * @return {MIXED} The results of the filtered data

     * @private

     */

    _revive = function (data, reviver) {

        var walk = function (o,key) {

            var k,v,value = o[key];

            if (value && typeof value === 'object') {

                for (k in value) {

                    if (value.hasOwnProperty(k)) {

                        v = walk(value, k);

                        if (v === undefined) {

                            delete value[k];

                        } else {

                            value[k] = v;

                        }

                    }

                }

            }

            return reviver.call(o,key,value);

        };

        return typeof reviver === 'function' ? walk({'':data},'') : data;

    },

    /**

     * Parse a JSON string, returning the native JavaScript representation.

     *

     * @param s {string} JSON string data

     * @param reviver {function} (optional) function(k,v) passed each key value

     *          pair of object literals, allowing pruning or altering values

     * @return {MIXED} the native JavaScript representation of the JSON string

     * @throws SyntaxError

     * @method parse

     * @static

     */

    // JavaScript implementation in lieu of native browser support.  Based on

    // the json2.js library from http://json.org

    _parse = function (s,reviver) {

        if (typeof s === 'string') {

            // Replace certain Unicode characters that are otherwise handled

            // incorrectly by some browser implementations.

            // NOTE: This modifies the input if such characters are found!

            s = s.replace(_UNICODE_EXCEPTIONS, _escapeException);

            // Test for any remaining invalid characters

            if (!_INVALID.test(s.replace(_ESCAPES,'@').

                                 replace(_VALUES,']').

                                 replace(_BRACKETS,''))) {

                // Eval the text into a JavaScript data structure, apply any

                // reviver function, and return

                return _revive( eval('(' + s + ')'), reviver );

            }

        }

        throw new SyntaxError('JSON.parse');

    },

    test;

// Test the level of native browser support

if (Native && Object.prototype.toString.call(Native) === '[object JSON]') {

    try {

        test = Native.parse('{"x":1}', function (k,v) {return k=='x' ? 2 : v;});

        switch (test.x) {

            case 1 : // Reviver not supported

                _parse = function (s,reviver) {

                    return _SIMPLE.test(s) ?

                            eval('(' + s + ')') :

                            _revive(Native.parse(s), reviver);

                };

                break;

            case 2 : // Full support

                _parse = function (s, reviver) {

                    return Native.parse(s, reviver);

                };

                break;

            // default is JS implementation

        }

    }

    catch (e) {} // defer to JS implementation

}

Y.mix(Y.namespace('JSON'),{ parse : _parse });

}, '3.0.0b1' );