    /**
     * @author Ed Spencer
     *
     * This singleton contains a set of validation functions that can be used to validate any type of data. They are most
     * often used in {@link Ext.data.Model Models}, where they are automatically set up and executed.
     */
    Ext.define('Ext.data.validations', {
        singleton: true,

        /**
         * @property {String} presenceMessage
         * The default error message used when a presence validation fails.
         */
        presenceMessage: 'must be present',

        /**
         * @property {String} lengthMessage
         * The default error message used when a length validation fails.
         */
        lengthMessage: 'is the wrong length',

        /**
         * @property {String} formatMessage
         * The default error message used when a format validation fails.
         */
        formatMessage: 'is the wrong format',

        /**
         * @property {String} inclusionMessage
         * The default error message used when an inclusion validation fails.
         */
        inclusionMessage: 'is not included in the list of acceptable values',

        /**
         * @property {String} exclusionMessage
         * The default error message used when an exclusion validation fails.
         */
        exclusionMessage: 'is not an acceptable value',

        /**
         * @property {String} emailMessage
         * The default error message used when an email validation fails
         */
        emailMessage: 'is not a valid email address',

        /**
         * @property {RegExp} emailRe
         * The regular expression used to validate email addresses
         */
        emailRe: /^([a-zA-Z0-9_\.\-])+\@(([a-zA-Z0-9\-])+\.)+([a-zA-Z0-9]{2,4})+$/,

        /**
         * Validates that the given value is present.
         * For example:
         *
         *     validations: [{type: 'presence', field: 'age'}]
         *
         * @param {Object} config Config object
         * @param {Object} value The value to validate
         * @return {Boolean} True if validation passed
         */
        presence: function(config, value) {
            // No configs read, so allow just value to be passed
            if (arguments.length === 1) {
                value = config;
            }

            //we need an additional check for zero here because zero is an acceptable form of present data
            return !!value || value === 0;
        },

        /**
         * Returns true if the given value is between the configured min and max values.
         * For example:
         *
         *     validations: [{type: 'length', field: 'name', min: 2}]
         *
         * @param {Object} config Config object
         * @param {String} value The value to validate
         * @return {Boolean} True if the value passes validation
         */
        length: function(config, value) {
            if (value === undefined || value === null) {
                return false;
            }

            var length = value.length,
                min    = config.min,
                max    = config.max;

            if ((min && length < min) || (max && length > max)) {
                return false;
            } else {
                return true;
            }
        },

        /**
         * Validates that an email string is in the correct format
         * @param {Object} config Config object
         * @param {String} email The email address
         * @return {Boolean} True if the value passes validation
         */
        email: function(config, email) {
            return Ext.data.validations.emailRe.test(email);
        },

        /**
         * Returns true if the given value passes validation against the configured `matcher` regex.
         * For example:
         *
         *     validations: [{type: 'format', field: 'username', matcher: /([a-z]+)[0-9]{2,3}/}]
         *
         * @param {Object} config Config object
         * @param {String} value The value to validate
         * @return {Boolean} True if the value passes the format validation
         */
        format: function(config, value) {
            return !!(config.matcher && config.matcher.test(value));
        },

        /**
         * Validates that the given value is present in the configured `list`.
         * For example:
         *
         *     validations: [{type: 'inclusion', field: 'gender', list: ['Male', 'Female']}]
         *
         * @param {Object} config Config object
         * @param {String} value The value to validate
         * @return {Boolean} True if the value is present in the list
         */
        inclusion: function(config, value) {
            return config.list && Ext.Array.indexOf(config.list,value) != -1;
        },

        /**
         * Validates that the given value is not present in the configured `list`.
         * For example:
         *
         *     validations: [{type: 'exclusion', field: 'username', list: ['Admin', 'Operator']}]
         *
         * @param {Object} config Config object
         * @param {String} value The value to validate
         * @return {Boolean} True if the value is not present in the list
         */
        exclusion: function(config, value) {
            return config.list && Ext.Array.indexOf(config.list,value) == -1;
        }
    });