[Glitch] Fix /share and cleanup and reorganize frontend locale loading

Port b0780cfeed to glitch-soc

Signed-off-by: Claire <claire.github-309c@sitedethib.com>

app/javascript/flavours/glitch/locales/load_locale.ts

@@ -0,0 +1,37 @@
+import { Semaphore } from 'async-mutex';
+
+import type { LocaleData } from './global_locale';
+import { isLocaleLoaded, setLocale } from './global_locale';
+
+const localeLoadingSemaphore = new Semaphore(1);
+
+export async function loadLocale() {
+  const locale = document.querySelector<HTMLElement>('html')?.lang || 'en';
+
+  // We use a Semaphore here so only one thing can try to load the locales at
+  // the same time. If one tries to do it while its in progress, it will wait
+  // for the initial load to finish before it is resumed (and will see that locale
+  // data is already loaded)
+  await localeLoadingSemaphore.runExclusive(async () => {
+    // if the locale is already set, then do nothing
+    if (isLocaleLoaded()) return;
+
+    const upstreamLocaleData = await import(
+      /* webpackMode: "lazy" */
+      /* webpackChunkName: "locales/vanilla/[request]" */
+      /* webpackInclude: /\.json$/ */
+      /* webpackPreload: true */
+      `mastodon/locales/${locale}.json`
+    ) as LocaleData['messages'];
+
+    const localeData = await import(
+      /* webpackMode: "lazy" */
+      /* webpackChunkName: "locales/glitch/[request]" */
+      /* webpackInclude: /\.json$/ */
+      /* webpackPreload: true */
+      `flavours/glitch/locales/${locale}.json`
+    ) as LocaleData['messages'];
+
+    setLocale({ messages: { ...upstreamLocaleData, ...localeData }, locale });
+  });
+}