From 9329dd1dc87e2274dd0a49ce8ea9d761af0269a5 Mon Sep 17 00:00:00 2001
From: Kyle Bowden <1393788+kyle-bowden@users.noreply.github.com>
Date: Thu, 28 Mar 2024 11:24:54 +0000
Subject: [PATCH] PLATUI-2829: Revert change to display backlink when referer
 is empty (#360)

---
 CHANGELOG.md                                  |  6 ++++
 package-lock.json                             |  2 +-
 package.json                                  |  2 +-
 .../back-link-helper/back-link-helper.js      | 34 ++++++++-----------
 .../back-link-helper/back-link-helper.test.js | 11 ++++--
 5 files changed, 32 insertions(+), 23 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 02394c42..8cbd5576 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -7,6 +7,12 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 
 ## [Unreleased]
 
+## [6.13.0] - 2024-03-27
+
+### Changed
+
+- Revert change to retain the back link even when the referrer is empty
+
 ## [6.12.0] - 2024-03-26
 
 ### Changed
diff --git a/package-lock.json b/package-lock.json
index 2d1c5b5b..c8c584f8 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -1,6 +1,6 @@
 {
   "name": "hmrc-frontend",
-  "version": "6.12.0",
+  "version": "6.13.0",
   "lockfileVersion": 1,
   "requires": true,
   "dependencies": {
diff --git a/package.json b/package.json
index cd2595da..6ba6b413 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "hmrc-frontend",
-  "version": "6.12.0",
+  "version": "6.13.0",
   "description": "Design patterns for HMRC frontends",
   "scripts": {
     "start": "gulp dev",
diff --git a/src/components/back-link-helper/back-link-helper.js b/src/components/back-link-helper/back-link-helper.js
index fc62c492..57538edd 100644
--- a/src/components/back-link-helper/back-link-helper.js
+++ b/src/components/back-link-helper/back-link-helper.js
@@ -5,27 +5,23 @@ function BackLinkHelper($module, window, document) {
 }
 
 BackLinkHelper.prototype.init = function init() {
-  const isReferrerExternal = () => {
-    // If there is no referrer, consider it on the same domain
-    if (!this.document.referrer) {
-      return false;
-    }
-
-    try {
-      const currentDomain = new URL(this.window.location.href).hostname;
-      const referrerDomain = new URL(this.document.referrer).hostname;
-
-      // Check if the referrer is not the same as the current domain
-      return currentDomain !== referrerDomain;
-    } catch (err) {
-      return false;
-    }
-  };
-
   // do nothing if History API is absent
   if (this.window.history) {
-    // hide the backlink if the referrer is on a different domain
-    if (isReferrerExternal()) {
+    // eslint-disable-next-line max-len
+    /* TODO: It remains unclear whether a check for the same domain is necessary for security reasons.
+       There may be user research suggesting considerations regarding the visibility of the
+       back link on refresh.
+       Currently, a page refresh sets the referer to empty, leading to the back link being hidden
+       under our existing logic.
+     */
+    // eslint-disable-next-line max-len
+    const referrerNotOnSameDomain = () => {
+      const referer = this.document.referrer;
+      return !referer || referer.indexOf(this.window.location.host) === -1;
+    };
+
+    // hide the backlink if the referrer is on a different domain or the referrer is not set
+    if (referrerNotOnSameDomain()) {
       this.$module.classList.add('hmrc-hidden-backlink');
     } else {
       // prevent resubmit warning
diff --git a/src/components/back-link-helper/back-link-helper.test.js b/src/components/back-link-helper/back-link-helper.test.js
index 9df76e34..8290a929 100644
--- a/src/components/back-link-helper/back-link-helper.test.js
+++ b/src/components/back-link-helper/back-link-helper.test.js
@@ -71,11 +71,18 @@ describe('/components/back-link-helper', () => {
       expect(mockWindow.history.back).toHaveBeenCalled();
     });
 
-    it('does not add .hmrc-hidden-backlink class to backlink when document referer is empty', () => {
+    it('adds .hmrc-hidden-backlink class to backlink when document referer is empty', () => {
       const sut = new BackLinkHelper(mockAnchorTag, mockWindow, { referrer: '' });
       sut.init();
 
-      expect(mockAnchorTag.classList.add.mock.calls).toHaveLength(0);
+      expect(mockAnchorTag.classList.add.mock.calls[0][0]).toBe('hmrc-hidden-backlink');
+    });
+
+    it('adds .hmrc-hidden-backlink class to backlink when document referer is null', () => {
+      const sut = new BackLinkHelper(mockAnchorTag, mockWindow, { referrer: null });
+      sut.init();
+
+      expect(mockAnchorTag.classList.add.mock.calls[0][0]).toBe('hmrc-hidden-backlink');
     });
 
     it('adds .hmrc-hidden-backlink class to backlink if document referer is on a different domain', () => {