    /**
     * @singleton
     * @alternateClassName Ext.form.VTypes
     *
     * This is a singleton object which contains a set of commonly used field validation functions
     * and provides a mechanism for creating reusable custom field validations.
     * The following field validation functions are provided out of the box:
     *
     * - {@link #alpha}
     * - {@link #alphanum}
     * - {@link #email}
     * - {@link #url}
     *
     * VTypes can be applied to a {@link Ext.form.field.Text Text Field} using the `{@link Ext.form.field.Text#vtype vtype}` configuration:
     *
     *     Ext.create('Ext.form.field.Text', {
     *         fieldLabel: 'Email Address',
     *         name: 'email',
     *         vtype: 'email' // applies email validation rules to this field
     *     });
     *
     * To create custom VTypes:
     *
     *     // custom Vtype for vtype:'time'
     *     var timeTest = /^([1-9]|1[0-9]):([0-5][0-9])(\s[a|p]m)$/i;
     *     Ext.apply(Ext.form.field.VTypes, {
     *         //  vtype validation function
     *         time: function(val, field) {
     *             return timeTest.test(val);
     *         },
     *         // vtype Text property: The error text to display when the validation function returns false
     *         timeText: 'Not a valid time.  Must be in the format "12:34 PM".',
     *         // vtype Mask property: The keystroke filter mask
     *         timeMask: /[\d\s:amp]/i
     *     });
     *
     * In the above example the `time` function is the validator that will run when field validation occurs,
     * `timeText` is the error message, and `timeMask` limits what characters can be typed into the field.
     * Note that the `Text` and `Mask` functions must begin with the same name as the validator function.
     *
     * Using a custom validator is the same as using one of the build-in validators - just use the name of the validator function
     * as the `{@link Ext.form.field.Text#vtype vtype}` configuration on a {@link Ext.form.field.Text Text Field}:
     *
     *     Ext.create('Ext.form.field.Text', {
     *         fieldLabel: 'Departure Time',
     *         name: 'departureTime',
     *         vtype: 'time' // applies custom time validation rules to this field
     *     });
     *
     * Another example of a custom validator:
     *
     *     // custom Vtype for vtype:'IPAddress'
     *     Ext.apply(Ext.form.field.VTypes, {
     *         IPAddress:  function(v) {
     *             return /^\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3}$/.test(v);
     *         },
     *         IPAddressText: 'Must be a numeric IP address',
     *         IPAddressMask: /[\d\.]/i
     *     });
     *
     * It's important to note that using {@link Ext#apply Ext.apply()} means that the custom validator function
     * as well as `Text` and `Mask` fields are added as properties of the `Ext.form.field.VTypes` singleton.
     */
    Ext.define('Ext.form.field.VTypes', (function(){
        // closure these in so they are only created once.
        var alpha = /^[a-zA-Z_]+$/,
            alphanum = /^[a-zA-Z0-9_]+$/,

            // http://en.wikipedia.org/wiki/Email_address#Local_part
            // http://stackoverflow.com/a/2049510
            // http://isemail.info/
            // http://blog.stevenlevithan.com/archives/capturing-vs-non-capturing-groups
            //
            // 1. Can begin with a double-quote ONLY IF the local part also ends in a double-quote.
            // 2. Can NOT BEGIN with a period.
            // 3. Can NOT END with a period.
            // 4. Can not have MORE THAN ONE period in a row.
            //
            // Let's break this down:
            //
            // ^(")?
            // The local part may begin with double-quotes, but only if it also ends with it.
            // See the back-reference.  Capturing.
            //
            // (?:[^\."])
            // Here we've defined that the local part cannot begin with a period or a double-quote.  Non-capturing.
            //
            // (?:(?:[\.])?(?:[\w\-!#$%&'*+/=?^_`{|}~]))*
            // After the first character is matched, the regex ensures that there is not more than one period
            // in a row.  Then, this nested grouping allows for zero or more of the accepted characters.
            // NOTE that this also ensures that any character not defined in the character class
            // is invalid as an ending character for the local part (such as the period).
            //
            // \1@
            // The local part of the address is a backreference to the first (and only) capturing group that allows
            // for a double-quote to wrap the local part of an email address.
            email = /^(")?(?:[^\."])(?:(?:[\.])?(?:[\w\-!#$%&'*+/=?^_`{|}~]))*\1@(\w[\-\w]*\.){1,5}([A-Za-z]){2,6}$/,
            url = /(((^https?)|(^ftp)):\/\/((([\-\w]+\.)+\w{2,3}(\/[%\-\w]+(\.\w{2,})?)*(([\w\-\.\?\\\/+@&#;`~=%!]*)(\.\w{2,})?)*)|(localhost|LOCALHOST))\/?)/i;

        // All these messages and functions are configurable
        return {
            singleton: true,
            alternateClassName: 'Ext.form.VTypes',

            /**
             * The function used to validate email addresses. Note that complete validation per the email RFC
             * specifications is very complex and beyond the scope of this class, although this function can be
             * overridden if a more comprehensive validation scheme is desired. See the validation section
             * of the [Wikipedia article on email addresses][1] for additional information. This implementation is
             * intended to validate the following types of emails:
             *
             * - `barney@example.de`
             * - `barney.rubble@example.com`
             * - `barney-rubble@example.coop`
             * - `barney+rubble@example.com`
             * - `barney'rubble@example.com`
             * - `b.arne.y_r.ubbl.e@example.com`
             * - `barney4rubble@example.com`
             * - `barney4rubble!@example.com`
             * - `_barney+rubble@example.com`
             * - `"barney+rubble"@example.com`
             *
             * [1]: http://en.wikipedia.org/wiki/E-mail_address
             *
             * @param {String} value The email address
             * @return {Boolean} true if the RegExp test passed, and false if not.
             */
            'email' : function(v){
                return email.test(v);
            },
            //<locale>
            /**
             * @property {String} emailText
             * The error text to display when the email validation function returns false.
             * Defaults to: 'This field should be an e-mail address in the format "user@example.com"'
             */
            'emailText' : 'This field should be an e-mail address in the format "user@example.com"',
            //</locale>
            /**
             * @property {RegExp} emailMask
             * The keystroke filter mask to be applied on email input. See the {@link #email} method for information about
             * more complex email validation. Defaults to: /[a-z0-9_\.\-@]/i
             */
            'emailMask' : /[\w.\-@'"!#$%&'*+/=?^_`{|}~]/i,

            /**
             * The function used to validate URLs
             * @param {String} value The URL
             * @return {Boolean} true if the RegExp test passed, and false if not.
             */
            'url' : function(v){
                return url.test(v);
            },
            //<locale>
            /**
             * @property {String} urlText
             * The error text to display when the url validation function returns false.
             * Defaults to: 'This field should be a URL in the format "http:/'+'/www.example.com"'
             */
            'urlText' : 'This field should be a URL in the format "http:/'+'/www.example.com"',
            //</locale>

            /**
             * The function used to validate alpha values
             * @param {String} value The value
             * @return {Boolean} true if the RegExp test passed, and false if not.
             */
            'alpha' : function(v){
                return alpha.test(v);
            },
            //<locale>
            /**
             * @property {String} alphaText
             * The error text to display when the alpha validation function returns false.
             * Defaults to: 'This field should only contain letters and _'
             */
            'alphaText' : 'This field should only contain letters and _',
            //</locale>
            /**
             * @property {RegExp} alphaMask
             * The keystroke filter mask to be applied on alpha input. Defaults to: /[a-z_]/i
             */
            'alphaMask' : /[a-z_]/i,

            /**
             * The function used to validate alphanumeric values
             * @param {String} value The value
             * @return {Boolean} true if the RegExp test passed, and false if not.
             */
            'alphanum' : function(v){
                return alphanum.test(v);
            },
            //<locale>
            /**
             * @property {String} alphanumText
             * The error text to display when the alphanumeric validation function returns false.
             * Defaults to: 'This field should only contain letters, numbers and _'
             */
            'alphanumText' : 'This field should only contain letters, numbers and _',
            //</locale>
            /**
             * @property {RegExp} alphanumMask
             * The keystroke filter mask to be applied on alphanumeric input. Defaults to: /[a-z0-9_]/i
             */
            'alphanumMask' : /[a-z0-9_]/i
        };
    }()));