From e462ac837e54f95ee1055cb0283a35a642cf3da7 Mon Sep 17 00:00:00 2001
From: Johan Preynat <johan.preynat@gmail.com>
Date: Fri, 15 Mar 2024 11:24:41 +0100
Subject: [PATCH] Redirect URLs containing uppercase characters to lowercase
 (#266)

* Add tests for normalizeURL

* Redirect requests containing uppercase in pathname to lowercase via normalizeURL

* Fix typo
---
 src/lib/middleware.test.ts | 28 +++++++++++++++++++++++++++-
 src/lib/middleware.ts      |  3 ++-
 src/middleware.ts          |  2 +-
 3 files changed, 30 insertions(+), 3 deletions(-)

diff --git a/src/lib/middleware.test.ts b/src/lib/middleware.test.ts
index 81dc48fd0..a61f300ef 100644
--- a/src/lib/middleware.test.ts
+++ b/src/lib/middleware.test.ts
@@ -1,6 +1,6 @@
 import { describe, it, expect } from 'bun:test';
 
-import { getURLLookupAlternatives } from './middleware';
+import { getURLLookupAlternatives, normalizeURL } from './middleware';
 
 describe('getURLLookupAlternatives', () => {
     it('should return all URLs up to the root', () => {
@@ -104,3 +104,29 @@ describe('getURLLookupAlternatives', () => {
         ]);
     });
 });
+
+describe('normalizeURL', () => {
+    it('should remove trailing slashes', () => {
+        expect(normalizeURL(new URL('https://docs.mycompany.com/hello/'))).toEqual(
+            new URL('https://docs.mycompany.com/hello'),
+        );
+    });
+
+    it('should remove duplicate slashes', () => {
+        expect(normalizeURL(new URL('https://docs.mycompany.com//hello//there'))).toEqual(
+            new URL('https://docs.mycompany.com/hello/there'),
+        );
+    });
+
+    it('should convert uppercase characters in the path to lowercase', () => {
+        expect(normalizeURL(new URL('https://docs.mycompany.com/Hello/My/pAge'))).toEqual(
+            new URL('https://docs.mycompany.com/hello/my/page'),
+        );
+    });
+
+    it('should not affect uppercase characters in querystring parameters', () => {
+        expect(normalizeURL(new URL('https://docs.mycompany.com/Hello/My/pAge?Q=MySearch'))).toEqual(
+            new URL('https://docs.mycompany.com/hello/my/page?Q=MySearch'),
+        );
+    });
+})
\ No newline at end of file
diff --git a/src/lib/middleware.ts b/src/lib/middleware.ts
index 50b5a55e7..1359ce94d 100644
--- a/src/lib/middleware.ts
+++ b/src/lib/middleware.ts
@@ -90,9 +90,10 @@ export function getURLLookupAlternatives(input: URL) {
 
 /**
  * Normalize a URL to remove duplicate slashes and trailing slashes
+ * and transform the pathname to lowercase.
  */
 export function normalizeURL(url: URL) {
     const result = new URL(url);
-    result.pathname = url.pathname.replace(/\/{2,}/g, '/').replace(/\/$/, '');
+    result.pathname = url.pathname.replace(/\/{2,}/g, '/').replace(/\/$/, '').toLowerCase();
     return result;
 }
diff --git a/src/middleware.ts b/src/middleware.ts
index be757aa01..5a347f70f 100644
--- a/src/middleware.ts
+++ b/src/middleware.ts
@@ -140,7 +140,7 @@ export async function middleware(request: NextRequest) {
         revision: resolved.revision,
     });
 
-    // Because of how Next will encode, we need to encode ourselves the pathname before reriting to it.
+    // Because of how Next will encode, we need to encode ourselves the pathname before rewriting to it.
     const rewritePathname = normalizePathname(encodePathname(resolved.pathname));
 
     console.log(`${request.method} (${resolved.space}) ${rewritePathname}`);