feat: mobile app package (#1075)

packages/mobile/src/Lib/PreferencesManager.ts

@@ -0,0 +1,71 @@
+import { ApplicationService, isNullOrUndefined, PrefKey, removeFromArray } from '@standardnotes/snjs'
+import { MobileApplication } from './Application'
+
+type Preferences = Record<PrefKey, any>
+type PreferencesObserver = () => Promise<void> | void
+export const LAST_EXPORT_DATE_KEY = 'LastExportDateKey'
+const PREFS_KEY = 'preferences'
+
+export class PreferencesManager extends ApplicationService {
+  private userPreferences!: Preferences
+  observers: PreferencesObserver[] = []
+
+  /** @override */
+  override async onAppLaunch() {
+    void super.onAppLaunch()
+    void this.loadPreferences()
+  }
+
+  override deinit() {
+    this.observers = []
+  }
+
+  /**
+   * Registers an observer for preferences loaded event
+   * @returns function that unregisters this observer
+   */
+  public addPreferencesLoadedObserver(callback: PreferencesObserver) {
+    this.observers.push(callback)
+    return () => {
+      removeFromArray(this.observers, callback)
+    }
+  }
+
+  notifyObserversOfPreferencesLoaded() {
+    for (const observer of this.observers) {
+      void observer()
+    }
+  }
+
+  get mobileApplication() {
+    return this.application as MobileApplication
+  }
+
+  private async loadPreferences() {
+    const preferences = await this.application.getValue(PREFS_KEY)
+    this.userPreferences = (preferences as Preferences) ?? {}
+    this.notifyObserversOfPreferencesLoaded()
+  }
+
+  private async saveSingleton() {
+    return this.application.setValue(PREFS_KEY, this.userPreferences)
+  }
+
+  private async savePreference(key: PrefKey, value: any) {
+    return this.application.setPreference(key, value)
+  }
+
+  getValue(key: PrefKey, defaultValue?: any) {
+    if (!this.userPreferences) {
+      return defaultValue
+    }
+    const value = this.application.getPreference(key)
+    return !isNullOrUndefined(value) ? value : defaultValue
+  }
+
+  async setUserPrefValue(key: PrefKey, value: any) {
+    this.userPreferences[key] = value
+    await this.saveSingleton()
+    await this.savePreference(key, value)
+  }
+}