refactor(rest): simplify manager.simplifyUrl (#2905)

* refactor(rest): simplify `manager.simplifyUrl`
The changes improve readability and performance by a small margin.

* fix tests

packages/rest/src/manager.ts

@@ -71,6 +71,7 @@ import type { CreateRestManagerOptions, RestManager, SendRequestOptions } from '
 
 // TODO: make dynamic based on package.json file
 const version = '19.0.0-alpha.1'
+const URL_PARTS_REGEX = /([a-z]+)\/(?:[0-9]{17,}(\/@me)?)/g
 
 export function createRestManager(options: CreateRestManagerOptions): RestManager {
   // Falsy token string check
@@ -912,20 +913,27 @@ export function createRestManager(options: CreateRestManagerOptions): RestManage
     // Credits: github.com/abalabahaha/eris lib/rest/RequestHandler.js#L397
     // Modified for our use-case
     simplifyUrl(url, method) {
-      let route = url
-        .replace(/\/([a-z-]+)\/(?:[0-9]{17,19})/g, function (match, p: string) {
-          return ['channels', 'guilds'].includes(p) ? match : `/${p}/x`
-        })
-        .replace(/\/reactions\/[^/]+/g, '/reactions/x')
+      let route = url.replace(URL_PARTS_REGEX, function (match, pattern: string) {
+        if (pattern.startsWith('channels') || pattern.startsWith('guilds')) {
+          return match
+        }
+
+        // GENERAL /reactions and /reactions/emoji/@me share the buckets
+        if (pattern.startsWith('reactions')) {
+          return 'reactions'
+        }
+
+        return `${pattern}/x`
+      })
 
-      // GENERAL /reactions and /reactions/emoji/@me share the buckets
       if (route.includes('/reactions')) {
-        route = route.substring(0, route.indexOf('/reactions') + '/reactions'.length)
+        // 10 is the length of `/reactions`
+        route = route.substring(0, route.indexOf('/reactions') + 10)
       }
 
       // Delete Message endpoint has its own rate limit
       if (method === 'DELETE' && route.endsWith('/messages/x')) {
-        route = method + route
+        route = 'D' + route
       }
 
       return route

packages/rest/tests/unit/manager.spec.ts

@@ -24,8 +24,8 @@ describe('[rest] manager', () => {
       version: 9,
       proxy: {
         baseUrl: 'https://localhost:8000',
-        authorization: token
-      }
+        authorization: token,
+      },
     } as const
 
     const rest = createRestManager(options)
@@ -80,7 +80,7 @@ describe('[rest] manager', () => {
         it('Will add method in front route if method is DELETE', () => {
           const rest = createRestManager({ token })
           expect(rest.simplifyUrl('/channels/555555555555555555/messages/555555555555555555', 'DELETE')).to.be.equal(
-            'DELETE/channels/555555555555555555/messages/x',
+            'D/channels/555555555555555555/messages/x',
           )
         })