feat: add snjs package

packages/snjs/lib/Services/AppService/ApplicationService.ts

@@ -0,0 +1,75 @@
+import { ApplicationEvent } from '@Lib/Application/Event'
+import { AbstractService, InternalEventBusInterface } from '@standardnotes/services'
+import { SNApplication } from '../../Application/Application'
+
+export class ApplicationService extends AbstractService {
+  private unsubApp!: () => void
+
+  constructor(protected application: SNApplication, protected override internalEventBus: InternalEventBusInterface) {
+    super(internalEventBus)
+    this.addAppEventObserverAfterSubclassesFinishConstructing()
+  }
+
+  override deinit() {
+    ;(this.application as unknown) = undefined
+
+    this.unsubApp()
+    ;(this.unsubApp as unknown) = undefined
+
+    super.deinit()
+  }
+
+  addAppEventObserverAfterSubclassesFinishConstructing() {
+    setTimeout(() => {
+      this.addAppEventObserver()
+    }, 0)
+  }
+
+  addAppEventObserver() {
+    if (this.application.isStarted()) {
+      void this.onAppStart()
+    }
+    if (this.application.isLaunched()) {
+      void this.onAppLaunch()
+    }
+
+    this.unsubApp = this.application.addEventObserver(async (event: ApplicationEvent) => {
+      await this.onAppEvent(event)
+      if (event === ApplicationEvent.Started) {
+        void this.onAppStart()
+      } else if (event === ApplicationEvent.Launched) {
+        void this.onAppLaunch()
+      } else if (event === ApplicationEvent.CompletedFullSync) {
+        this.onAppFullSync()
+      } else if (event === ApplicationEvent.CompletedIncrementalSync) {
+        this.onAppIncrementalSync()
+      } else if (event === ApplicationEvent.KeyStatusChanged) {
+        void this.onAppKeyChange()
+      }
+    })
+  }
+
+  async onAppEvent(_event: ApplicationEvent) {
+    /** Optional override */
+  }
+
+  async onAppStart() {
+    /** Optional override */
+  }
+
+  async onAppLaunch() {
+    /** Optional override */
+  }
+
+  async onAppKeyChange() {
+    /** Optional override */
+  }
+
+  onAppIncrementalSync() {
+    /** Optional override */
+  }
+
+  onAppFullSync() {
+    /** Optional override */
+  }
+}