From 8c2366bf56b182fb199f44ddd8f0d66d2419dcad Mon Sep 17 00:00:00 2001
From: Thomas Turrell-Croft <tom@berrycloud.co.uk>
Date: Wed, 15 Dec 2021 21:38:55 +0000
Subject: [PATCH] Add support for Google Analitics global site tag

---
 .../src/lib/plugins-google-analytics.ts       | 39 +++++++++++++------
 1 file changed, 28 insertions(+), 11 deletions(-)

diff --git a/libs/plugins/google-analytics/src/lib/plugins-google-analytics.ts b/libs/plugins/google-analytics/src/lib/plugins-google-analytics.ts
index 0829191eb..a7dbf6e64 100644
--- a/libs/plugins/google-analytics/src/lib/plugins-google-analytics.ts
+++ b/libs/plugins/google-analytics/src/lib/plugins-google-analytics.ts
@@ -1,4 +1,4 @@
-import { registerPlugin, getMyConfig } from '@scullyio/scully';
+import { getMyConfig, registerPlugin } from '@scullyio/scully';
 
 export const GoogleAnalytics = 'googleAnalytics';
 
@@ -8,9 +8,32 @@ export const googleAnalyticsPlugin = async (html: string): Promise<string> => {
   if (!googleAnalyticsConfig) {
     throw new Error('googleAnalytics plugin missing Global Site Tag');
   }
-  const siteTag: string = googleAnalyticsConfig['globalSiteTag'];
 
-  const googleAnalyticsScript = `
+  const googleAnalyticsScript = getSnippet(googleAnalyticsConfig['globalSiteTag']);
+
+  return html.replace(/<\/head/i, `${googleAnalyticsScript}</head`);
+};
+
+const validator = async () => [];
+
+registerPlugin('postProcessByHtml', GoogleAnalytics, googleAnalyticsPlugin, validator);
+
+function getSnippet(siteTag: string) {
+  if (siteTag.startsWith('G-')) {
+    return `
+<!-- Global site tag (gtag.js) - Google Analytics -->
+<script async src="https://www.googletagmanager.com/gtag/js?id=${siteTag}"></script>
+<script>
+  window.dataLayer = window.dataLayer || [];
+  function gtag(){dataLayer.push(arguments);}
+  gtag('js', new Date());
+
+  gtag('config', '${siteTag}');
+</script>
+`;
+  }
+
+  return `
 <!-- Google Analytics -->
   <script sk>
   window.ga=window.ga||function(){(ga.q=ga.q||[]).push(arguments)};ga.l=+new Date;
@@ -18,12 +41,6 @@ export const googleAnalyticsPlugin = async (html: string): Promise<string> => {
   ga('send', 'pageview');
   </script>
   <script sk async src='https://www.google-analytics.com/analytics.js'></script>
-  <!-- End Google Analytics -->
+<!-- End Google Analytics -->
 `;
-
-  return html.replace(/<\/head/i, `${googleAnalyticsScript}</head`);
-};
-
-const validator = async () => [];
-
-registerPlugin('postProcessByHtml', GoogleAnalytics, googleAnalyticsPlugin, validator);
+}