fix: enable starting the app without backend

Closes #223

frontend/app/src/app/modules/config/config.provider.spec.ts

@@ -67,7 +67,8 @@ describe('ConfigProvider', () => {
 
   it('should fetch app configuration', async () => {
     spyOn(configProvider.client, 'handshake').and.returnValue(Promise.resolve(sampleIndexResponse));
-    const result = await configProvider.fetch();
+    await configProvider.fetch();
+    const result = configProvider.config;
     expect(result).toEqual(sampleIndexResponse);
   });
 
@@ -110,7 +111,7 @@ describe('ConfigProvider', () => {
     expect(storageProviderSpy.has).toHaveBeenCalled();
     expect(storageProviderSpy.get).toHaveBeenCalledTimes(0);
     expect(configProvider.client.handshake).toHaveBeenCalled();
-    expect(await configProvider.getValue('name')).toEqual(sampleIndexResponse.app.name);
+    expect(configProvider.getValue('name')).toEqual(sampleIndexResponse.app.name);
   });
 
   it('should throw error on failed initialisation', async () => {
@@ -192,4 +193,31 @@ describe('ConfigProvider', () => {
 
     expect(configProvider.getValue('name')).toEqual(sampleIndexResponse.app.name);
   });
+
+  it('should fetch new config from remote on init', async () => {
+    storageProviderSpy.has.and.returnValue(Promise.resolve(true));
+    storageProviderSpy.get.and.returnValue(Promise.resolve(sampleIndexResponse));
+    spyOn(configProvider, 'fetch');
+    await configProvider.init();
+
+    expect(configProvider.fetch).toHaveBeenCalled();
+  });
+
+  it('should update the local config with the one from remote', async () => {
+    storageProviderSpy.has.and.returnValue(Promise.resolve(true));
+    storageProviderSpy.get.and.returnValue(Promise.resolve(sampleIndexResponse));
+    const newConfig = structuredClone(sampleIndexResponse);
+    newConfig.app.name = 'New app name';
+    spyOn(configProvider.client, 'handshake').and.returnValue(Promise.resolve(newConfig));
+    await configProvider.init();
+
+    // Validate that the initial configuration is loaded
+    expect(configProvider.getValue('name')).toEqual(sampleIndexResponse.app.name);
+
+    // Fetch the new configuration from the remote
+    await configProvider.fetch();
+
+    // Validate that the new configuration is now set
+    expect(configProvider.getValue('name')).toEqual(newConfig.app.name);
+  });
 });

frontend/app/src/app/modules/config/config.provider.ts

@@ -83,17 +83,20 @@ export class ConfigProvider {
   /**
    * Fetches configuration from backend
    */
-  async fetch(): Promise<SCIndexResponse> {
+  async fetch(): Promise<void> {
     try {
       const isOffline = await firstValueFrom(this.internetConnectionService.offline$);
       if (isOffline) {
         throw new Error('Device is offline.');
       } else {
-        return await this.client.handshake(this.scVersion);
+        const fetchedConfig: SCIndexResponse = await this.client.handshake(this.scVersion);
+        await this.set(fetchedConfig);
+        this.logger.log(`Configuration updated from remote`);
       }
     } catch (error) {
       const error_ = error instanceof Error ? new ConfigFetchError(error.message) : new ConfigFetchError();
-      throw error_;
+      this.logger.warn(`Failed to fetch remote configuration:`, error_);
+      throw error_; // Rethrow the error to handle it in init()
     }
   }
 
@@ -121,40 +124,33 @@ export class ConfigProvider {
 
   /**
    * Initialises the ConfigProvider
-   * @throws ConfigInitError if no configuration could be loaded.
-   * @throws WrongConfigVersionInStorage if fetch failed and saved config has wrong SCVersion
+   * @throws ConfigInitError if no configuration could be loaded both locally and remote.
    */
   async init(): Promise<void> {
-    let loadError;
-    let fetchError;
-    // load saved configuration
     try {
+      // Attempt to load the configuration from local storage
       this.config = await this.loadLocal();
       this.firstSession = false;
       this.logger.log(`initialised configuration from storage`);
+
+      // Check if the stored configuration has the correct version
       if (this.config.backend.SCVersion.split('.')[0] !== this.scVersion.split('.')[0]) {
-        loadError = new WrongConfigVersionInStorage(this.scVersion, this.config.backend.SCVersion);
+        throw new WrongConfigVersionInStorage(this.scVersion, this.config.backend.SCVersion);
       }
-    } catch (error) {
-      loadError = error;
-    }
-    // fetch remote configuration from backend
-    try {
-      const fetchedConfig: SCIndexResponse = await this.fetch();
-      await this.set(fetchedConfig);
-      this.logger.log(`initialised configuration from remote`);
-    } catch (error) {
-      fetchError = error;
-    }
-    // check for occurred errors and throw them
-    if (loadError !== undefined && fetchError !== undefined) {
-      throw new ConfigInitError();
-    }
-    if (loadError !== undefined) {
+
+      // Fetch the remote configuration in a non-blocking manner
+      void this.fetch();
+    } catch (loadError) {
       this.logger.warn(loadError);
-    }
-    if (fetchError !== undefined) {
-      this.logger.warn(fetchError);
+
+      try {
+        // If local loading fails, immediately try to fetch the configuration from remote
+        await this.fetch();
+      } catch (fetchError) {
+        this.logger.warn(`Failed to fetch remote configuration:`, fetchError);
+        // If both local loading and remote fetching fail, throw ConfigInitError
+        throw new ConfigInitError();
+      }
     }
   }