From aa846a6af212e5da2eacd3ad3a335f2a104c9183 Mon Sep 17 00:00:00 2001
From: Jakob Ackermann <jakob.ackermann@overleaf.com>
Date: Thu, 28 Oct 2021 10:34:50 +0200
Subject: [PATCH] Merge pull request #5558 from
 overleaf/jpa-ta-canonical-url-tag

[web] add a canonical tag to gallery/learn/blog

GitOrigin-RevId: c6b9e84a0dbf04e44dbc507ae5dbf9ef2d95b8cc
---
 services/web/app/src/Features/Helpers/UrlHelper.js | 14 ++++++++++++++
 services/web/app/views/_metadata.pug               |  4 ++++
 2 files changed, 18 insertions(+)

diff --git a/services/web/app/src/Features/Helpers/UrlHelper.js b/services/web/app/src/Features/Helpers/UrlHelper.js
index d75eaccfc6..38d825e1e0 100644
--- a/services/web/app/src/Features/Helpers/UrlHelper.js
+++ b/services/web/app/src/Features/Helpers/UrlHelper.js
@@ -1,6 +1,19 @@
 const Settings = require('@overleaf/settings')
 const { URL } = require('url')
 
+const PROTO = new URL(Settings.siteUrl).protocol
+
+function getCanonicalURL(req, url) {
+  const origin = `${PROTO}//${req.headers.host}`
+  url = new URL(url || req.originalUrl, origin)
+  if (url.pathname.endsWith('/')) {
+    url.pathname = url.pathname.replace(/\/+$/, '')
+  }
+  url.search = ''
+  url.hash = ''
+  return url.href
+}
+
 function getSafeRedirectPath(value) {
   const baseURL = Settings.siteUrl // base URL is required to construct URL from path
   const url = new URL(value, baseURL)
@@ -12,6 +25,7 @@ function getSafeRedirectPath(value) {
 }
 
 const UrlHelper = {
+  getCanonicalURL,
   getSafeRedirectPath,
   wrapUrlWithProxy(url) {
     // TODO: Consider what to do for Community and Enterprise edition?
diff --git a/services/web/app/views/_metadata.pug b/services/web/app/views/_metadata.pug
index 14f84c85d1..c203c84e4f 100644
--- a/services/web/app/views/_metadata.pug
+++ b/services/web/app/views/_metadata.pug
@@ -113,3 +113,7 @@ link(rel="icon", href="/favicon.ico")
 link(rel="icon", sizes="192x192", href="/touch-icon-192x192.png")
 link(rel="apple-touch-icon-precomposed", href="/apple-touch-icon-precomposed.png")
 link(rel="mask-icon", href="/mask-favicon.svg", color="#138A07")
+
+//- Canonical Tag for SEO
+if (metadata && metadata.canonicalURL)
+	link(rel="canonical" href=metadata.canonicalURL)