let GoogleAnalytics = (() => {
    /**
     * Returns a string that represents the javascript that is required to insert the Google Analytics scripts
     * into a webpage.
     * @param tagId Google UA/G/AW/DC Property ID to use with the Google Analytics script.
     * @returns {string}
     */
    function getGoogleAnalyticsScript(tagId) {
        return "<script async src=\"https://www.googletagmanager.com/gtag/js?id=" + tagId + "\"></script>" +
            "<script>window.dataLayer = window.dataLayer || []; function gtag(){dataLayer.push(arguments);} gtag('js', new Date());gtag('config', '" + tagId + "'); </script>";
    }

    /**
     * Returns true if the tag conforms to the format of 1-2 Letters followed by a dash and 8 numbers.
     * This should take care of the following property tag formats:
     * UA-########, G-########, AW-########, DC-########
     * @param {String} tagInput Google UA/G/AW/DC Property ID
     * @returns {boolean}
     */
    function isValidTag(tagInput) {
        const re = /^\w{1,2}-\d{8}$/g;
        return tagInput.match(re) != null;
    }
    return {
        getGoogleAnalyticsScript: getGoogleAnalyticsScript,
        isValidTag: isValidTag
    };
})();

module.exports = GoogleAnalytics;