Fix ANR-like bug when resuming MainActivity.

app/src/main/java/org/thoughtcrime/securesms/notifications/SlowNotificationsViewModel.kt

@@ -0,0 +1,68 @@
+/*
+ * Copyright 2023 Signal Messenger, LLC
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
+package org.thoughtcrime.securesms.notifications
+
+import android.os.Build
+import androidx.lifecycle.ViewModel
+import io.reactivex.rxjava3.android.schedulers.AndroidSchedulers
+import io.reactivex.rxjava3.core.Observable
+import io.reactivex.rxjava3.core.Single
+import io.reactivex.rxjava3.schedulers.Schedulers
+import io.reactivex.rxjava3.subjects.BehaviorSubject
+import org.thoughtcrime.securesms.notifications.SlowNotificationHeuristics.isHavingDelayedNotifications
+import org.thoughtcrime.securesms.notifications.SlowNotificationHeuristics.isPotentiallyCausedByBatteryOptimizations
+import org.thoughtcrime.securesms.notifications.SlowNotificationHeuristics.shouldPromptBatterySaver
+import org.thoughtcrime.securesms.notifications.SlowNotificationHeuristics.shouldPromptUserForLogs
+import java.util.concurrent.TimeUnit
+
+/**
+ * View model for checking for slow notifications and if we should prompt the user with help or for information.
+ */
+class SlowNotificationsViewModel : ViewModel() {
+
+  private val checkSubject = BehaviorSubject.create<Unit>()
+
+  val slowNotificationState: Observable<State>
+
+  init {
+    slowNotificationState = checkSubject
+      .subscribeOn(Schedulers.io())
+      .observeOn(Schedulers.io())
+      .throttleFirst(1, TimeUnit.MINUTES)
+      .switchMapSingle {
+        checkHeuristics()
+      }
+      .distinctUntilChanged()
+      .observeOn(AndroidSchedulers.mainThread())
+  }
+
+  fun checkSlowNotificationHeuristics() {
+    checkSubject.onNext(Unit)
+  }
+
+  private fun checkHeuristics(): Single<State> {
+    return Single.fromCallable {
+      var state = State.NONE
+      if (isHavingDelayedNotifications()) {
+        if (isPotentiallyCausedByBatteryOptimizations() && Build.VERSION.SDK_INT >= 23) {
+          if (shouldPromptBatterySaver()) {
+            state = State.PROMPT_BATTERY_SAVER_DIALOG
+          }
+        } else if (shouldPromptUserForLogs()) {
+          state = State.PROMPT_DEBUGLOGS
+        }
+      }
+
+      return@fromCallable state
+    }.subscribeOn(Schedulers.io())
+  }
+
+  enum class State {
+    NONE,
+    PROMPT_BATTERY_SAVER_DIALOG,
+    PROMPT_DEBUGLOGS
+  }
+}