1 files changed, 47 insertions, 0 deletions
diff --git a/packages/sw/src/scripts/lang.ts b/packages/sw/src/scripts/lang.ts
new file mode 100644
index 0000000000..2d05404ef9
--- /dev/null
+++ b/packages/sw/src/scripts/lang.ts
@@ -0,0 +1,47 @@
+/*
+ * Language manager for SW
+ */
+declare var self: ServiceWorkerGlobalScope;
+
+import { get, set } from 'idb-keyval';
+import { I18n } from '@/scripts/i18n';
+
+class SwLang {
+	public cacheName = `mk-cache-${_VERSION_}`;
+
+	public lang: Promise<string> = get('lang').then(async prelang => {
+		if (!prelang) return 'en-US';
+		return prelang;
+	});
+
+	public setLang(newLang: string) {
+		this.lang = Promise.resolve(newLang);
+		set('lang', newLang);
+		return this.fetchLocale();
+	}
+
+	public i18n: Promise<I18n<any>> | null = null;
+
+	public fetchLocale() {
+		return this.i18n = this._fetch();
+	}
+
+	private async _fetch() {
+		// Service Workerは何度も起動しそのたびにlocaleを読み込むので、CacheStorageを使う
+		const localeUrl = `/assets/locales/${await this.lang}.${_VERSION_}.json`;
+		let localeRes = await caches.match(localeUrl);
+
+		// _DEV_がtrueの場合は常に最新化
+		if (!localeRes || _DEV_) {
+			localeRes = await fetch(localeUrl);
+			const clone = localeRes?.clone();
+			if (!clone?.clone().ok) Error('locale fetching error');
+
+			caches.open(this.cacheName).then(cache => cache.put(localeUrl, clone));
+		}
+
+		return new I18n(await localeRes.json());
+	}
+}
+
+export const swLang = new SwLang();