Move cache pruning to a WorkManager worker (#3649)

- Extend what was `NotificationWorkerFactory` to `WorkerFactory`. This
  can construct arbitrary Workers as long as they provide their own
  Factory for construction.

  The per-Worker factory contains any injected components just for that
  worker type, keeping `WorkerFactory` clean.

- Move `NotificationWorkerFactory` to the new model.

- Implement `PruneCacheWorker`, and remove the code from
 `CachedTimelineViewModel`.

- Create the periodic worker in `TuskyApplication`, ensuring that the
  database is only pruned when the device is idle.

app/src/main/java/com/keylesspalace/tusky/components/notifications/NotificationHelper.java

@@ -63,6 +63,7 @@ import com.keylesspalace.tusky.entity.Status;
 import com.keylesspalace.tusky.receiver.SendStatusBroadcastReceiver;
 import com.keylesspalace.tusky.util.StringUtils;
 import com.keylesspalace.tusky.viewdata.PollViewDataKt;
+import com.keylesspalace.tusky.worker.NotificationWorker;
 
 import java.util.ArrayList;
 import java.util.Collections;

app/src/main/java/com/keylesspalace/tusky/components/notifications/NotificationWorker.kt

@@ -1,51 +0,0 @@
-/* Copyright 2020 Tusky Contributors
- *
- * This file is part of Tusky.
- *
- * Tusky is free software: you can redistribute it and/or modify it under the terms of the GNU
- * Lesser General Public License as published by the Free Software Foundation, either version 3 of
- * the License, or (at your option) any later version.
- *
- * Tusky is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even
- * the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser
- * General Public License for more details.
- *
- * You should have received a copy of the GNU Lesser General Public License along with Tusky. If
- * not, see <http://www.gnu.org/licenses/>. */
-
-package com.keylesspalace.tusky.components.notifications
-
-import android.content.Context
-import androidx.work.ListenableWorker
-import androidx.work.Worker
-import androidx.work.WorkerFactory
-import androidx.work.WorkerParameters
-import javax.inject.Inject
-
-class NotificationWorker(
-    context: Context,
-    params: WorkerParameters,
-    private val notificationsFetcher: NotificationFetcher
-) : Worker(context, params) {
-
-    override fun doWork(): Result {
-        notificationsFetcher.fetchAndShow()
-        return Result.success()
-    }
-}
-
-class NotificationWorkerFactory @Inject constructor(
-    private val notificationsFetcher: NotificationFetcher
-) : WorkerFactory() {
-
-    override fun createWorker(
-        appContext: Context,
-        workerClassName: String,
-        workerParameters: WorkerParameters
-    ): ListenableWorker? {
-        if (workerClassName == NotificationWorker::class.java.name) {
-            return NotificationWorker(appContext, workerParameters, notificationsFetcher)
-        }
-        return null
-    }
-}

app/src/main/java/com/keylesspalace/tusky/components/timeline/viewmodel/CachedTimelineViewModel.kt

@@ -50,14 +50,11 @@ import com.keylesspalace.tusky.util.EmptyPagingSource
 import com.keylesspalace.tusky.viewdata.StatusViewData
 import kotlinx.coroutines.Dispatchers
 import kotlinx.coroutines.asExecutor
-import kotlinx.coroutines.delay
 import kotlinx.coroutines.flow.flowOn
 import kotlinx.coroutines.flow.map
 import kotlinx.coroutines.launch
 import retrofit2.HttpException
 import javax.inject.Inject
-import kotlin.time.DurationUnit
-import kotlin.time.toDuration
 
 /**
  * TimelineViewModel that caches all statuses in a local database
@@ -107,16 +104,6 @@ class CachedTimelineViewModel @Inject constructor(
         .flowOn(Dispatchers.Default)
         .cachedIn(viewModelScope)
 
-    init {
-        viewModelScope.launch {
-            delay(5.toDuration(DurationUnit.SECONDS)) // delay so the db is not locked during initial ui refresh
-            accountManager.activeAccount?.id?.let { accountId ->
-                db.timelineDao().cleanup(accountId, MAX_STATUSES_IN_CACHE)
-                db.timelineDao().cleanupAccounts(accountId)
-            }
-        }
-    }
-
     override fun updatePoll(newPoll: Poll, status: StatusViewData.Concrete) {
         // handled by CacheUpdater
     }