core-plugin-api: split AppTranslationApi into AppLanguageApi and TranslationApi

Signed-off-by: Patrik Oldsberg <poldsberg@gmail.com>

packages/core-app-api/src/apis/implementations/AppTranslationApi/AppTranslationImpl.ts

@@ -136,22 +136,6 @@ class ResourceLoader {
   }
 }
 
-/** @alpha */
-export interface TranslationOptions {
-  /* no options supported for now */
-}
-
-export type TranslationSnapshot<TMessages extends { [key in string]: string }> =
-
-    | { ready: false }
-    | {
-        ready: true;
-        t<TKey extends keyof TMessages>(
-          key: TKey,
-          options?: TranslationOptions,
-        ): TMessages[TKey];
-      };
-
 /** @alpha */
 export class AppTranslationApiImpl implements AppTranslationApi {
   static create(options?: ExperimentalI18n) {

packages/core-plugin-api/src/apis/definitions/AppLanguageApi.ts

@@ -14,20 +14,23 @@
  * limitations under the License.
  */
 
-import { type i18n } from 'i18next';
-import { TranslationRef } from '../../translation';
 import { ApiRef, createApiRef } from '@backstage/core-plugin-api';
+import { Observable } from '@backstage/types';
 
 /** @alpha */
-export type AppTranslationApi = {
-  getI18n(): i18n;
+export type AppLanguageApi = {
+  getAvailableLanguages(): { languages: string[] };
 
-  addResource(resource: TranslationRef): void;
+  setLanguage(language?: string): void;
+
+  getLanguage(): { language: string };
+
+  language$(): Observable<{ language: string }>;
 };
 
 /**
  * @alpha
  */
-export const appTranslationApiRef: ApiRef<AppTranslationApi> = createApiRef({
-  id: 'core.translation',
+export const appLanguageApiRef: ApiRef<AppLanguageApi> = createApiRef({
+  id: 'core.applanguage',
 });

packages/core-plugin-api/src/apis/definitions/TranslationApi.ts

@@ -0,0 +1,51 @@
+/*
+ * Copyright 2023 The Backstage Authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+import { ApiRef, createApiRef } from '@backstage/core-plugin-api';
+import { Observable } from '@backstage/types';
+import { TranslationRef } from '../../translation';
+
+/** @alpha */
+export interface TranslationOptions {
+  /* no options supported for now */
+}
+
+export type TranslationFunction<TMessages extends { [key in string]: string }> =
+  <TKey extends keyof TMessages>(
+    key: TKey,
+    options?: TranslationOptions,
+  ) => TMessages[TKey];
+
+export type TranslationSnapshot<TMessages extends { [key in string]: string }> =
+  { ready: false } | { ready: true; t: TranslationFunction<TMessages> };
+
+/** @alpha */
+export type TranslationApi = {
+  getTranslation<TMessages extends { [key in string]: string }>(
+    translationRef: TranslationRef<string, TMessages>,
+  ): TranslationSnapshot<TMessages>;
+
+  translation$<TMessages extends { [key in string]: string }>(
+    translationRef: TranslationRef<string, TMessages>,
+  ): Observable<TranslationSnapshot<TMessages>>;
+};
+
+/**
+ * @alpha
+ */
+export const translationApiRef: ApiRef<TranslationApi> = createApiRef({
+  id: 'core.translation',
+});

packages/core-plugin-api/src/apis/definitions/alpha.ts

@@ -13,4 +13,5 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-export * from './AppTranslationApi';
+export * from './TranslationApi';
+export * from './AppLanguageApi';