var JSONPRequest = Y.JSONPRequest,
    getByPath    = Y.Object.getValue,
    noop         = function () {};

/**
 * Adds support for parsing complex callback identifiers from the jsonp url.
 * This includes callback=foo[1]bar.baz["goo"] as well as referencing methods
 * in the YUI instance.
 *
 * @module jsonp
 * @submodule jsonp-url
 * @for JSONPRequest
 */

Y.mix(JSONPRequest.prototype, {
    /**
     * RegExp used by the default URL formatter to insert the generated callback
     * name into the JSONP url.  Looks for a query param callback=.  If a value
     * is assigned, it will be clobbered.
     *
     * @property _pattern
     * @type RegExp
     * @default /\bcallback=.*?(?=&|$)/i
     * @protected
     */
    _pattern: /\bcallback=(.*?)(?=&|$)/i,

    /**
     * Template used by the default URL formatter to add the callback function
     * name to the url.
     *
     * @property _template
     * @type String
     * @default "callback={callback}"
     * @protected
     */
    _template: "callback={callback}",

    /**
     * <p>Parses the url for a callback named explicitly in the string.
     * Override this if the target JSONP service uses a different query
     * parameter or url format.</p>
     *
     * <p>If the callback is declared inline, the corresponding function will
     * be returned.  Otherwise null.</p>
     *
     * @method _defaultCallback
     * @param url {String} the url to search in
     * @return {Function} the callback function if found, or null
     * @protected
     */
    _defaultCallback: function (url) {
        var match = url.match(this._pattern),
            keys  = [],
            i = 0,
            locator, path, callback;

        if (match) {
            // Strip the ["string keys"] and [1] array indexes
            locator = match[1]
                .replace(/\[(['"])(.*?)\1\]/g,
                    function (x, $1, $2) {
                        keys[i] = $2;
                        return '.@' + (i++);
                    })
                .replace(/\[(\d+)\]/g,
                    function (x, $1) {
                        keys[i] = parseInt($1, 10) | 0;
                        return '.@' + (i++);
                    })
                .replace(/^\./, ''); // remove leading dot

            // Validate against problematic characters.
            if (!/[^\w\.\$@]/.test(locator)) {
                path = locator.split('.');
                for (i = path.length - 1; i >= 0; --i) {
                    if (path[i].charAt(0) === '@') {
                        path[i] = keys[parseInt(path[i].substr(1), 10)];
                    }
                }

                // First look for a global function, then the Y, then try the Y
                // again from the second token (to support "callback=Y.handler")
                callback = getByPath(Y.config.win, path) ||
                           getByPath(Y, path) ||
                           getByPath(Y, path.slice(1));
            }
        }

        return callback || noop;
    },

    /**
     * URL formatter that looks for callback= in the url and appends it
     * if not present.  The supplied proxy name will be assigned to the query
     * param.  Override this method by passing a function as the
     * &quot;format&quot; property in the config object to the constructor.
     *
     * @method _format
     * @param url { String } the original url
     * @param proxy {String} the function name that will be used as a proxy to
     *      the configured callback methods.
     * @return {String} fully qualified JSONP url
     * @protected
     */
    _format: function (url, proxy) {
        var callback = this._template.replace(/\{callback\}/, proxy),
            lastChar;

        if (this._pattern.test(url)) {
            return url.replace(this._pattern, callback);
        } else {
            lastChar = url.slice(-1);
            if (lastChar !== '&' && lastChar !== '?') {
                url += (url.indexOf('?') > -1) ? '&' : '?';
            }
            return url + callback;
        }
    }

}, true);