Split hooks.ts into hooks.client.ts & hooks.server.ts

packages/editor/src/hooks.server.ts

 import type { Handle } from "@sveltejs/kit"
 import { sequence } from "@sveltejs/kit/hooks"
 
+import {
+  allLanguageCodes,
+  defaultLanguageCode,
+  type LanguageCode,
+} from "$lib/i18n"
 import { githubHandler } from "$lib/server/github_handler"
 import { openIdConnectHandler } from "$lib/server/openid_connect_handler"
 import { csrfHandler } from "$lib/server/csrf_handler"
@@ -14,4 +19,17 @@ export const handle: Handle = sequence(
   userHandler,
   githubHandler,
   openIdConnectHandler,
+  async ({ event, resolve }) => {
+    const pathname = event.url.pathname
+    const match = pathname.match(/^\/([a-z]{2})(\/|$)/)
+    const languageCode =
+      match === null
+        ? defaultLanguageCode
+        : allLanguageCodes.includes(match[1] as LanguageCode)
+          ? (match[1] as LanguageCode)
+          : defaultLanguageCode
+    return resolve(event, {
+      transformPageChunk: ({ html }) => html.replace("%lang%", languageCode),
+    })
+  },
 )