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/worker/NotificationWorker.kt

@@ -0,0 +1,44 @@
+/*
+ * Copyright 2023 Tusky Contributors
+ *
+ * This file is a part of Tusky.
+ *
+ * This program is free software; you can redistribute it and/or modify it under the terms of the
+ * GNU 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 General
+ * Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along with Tusky; if not,
+ * see <http://www.gnu.org/licenses>.
+ */
+
+package com.keylesspalace.tusky.worker
+
+import android.content.Context
+import androidx.work.Worker
+import androidx.work.WorkerParameters
+import com.keylesspalace.tusky.components.notifications.NotificationFetcher
+import javax.inject.Inject
+
+/** Fetch and show new notifications. */
+class NotificationWorker(
+    appContext: Context,
+    params: WorkerParameters,
+    private val notificationsFetcher: NotificationFetcher
+) : Worker(appContext, params) {
+    override fun doWork(): Result {
+        notificationsFetcher.fetchAndShow()
+        return Result.success()
+    }
+
+    class Factory @Inject constructor(
+        private val notificationsFetcher: NotificationFetcher
+    ) : ChildWorkerFactory {
+        override fun createWorker(appContext: Context, params: WorkerParameters): Worker {
+            return NotificationWorker(appContext, params, notificationsFetcher)
+        }
+    }
+}

app/src/main/java/com/keylesspalace/tusky/worker/PruneCacheWorker.kt

@@ -0,0 +1,58 @@
+/*
+ * Copyright 2023 Tusky Contributors
+ *
+ * This file is a part of Tusky.
+ *
+ * This program is free software; you can redistribute it and/or modify it under the terms of the
+ * GNU 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 General
+ * Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along with Tusky; if not,
+ * see <http://www.gnu.org/licenses>.
+ */
+
+package com.keylesspalace.tusky.worker
+
+import android.content.Context
+import android.util.Log
+import androidx.work.CoroutineWorker
+import androidx.work.ListenableWorker
+import androidx.work.WorkerParameters
+import com.keylesspalace.tusky.db.AccountManager
+import com.keylesspalace.tusky.db.AppDatabase
+import javax.inject.Inject
+
+/** Prune the database cache of old statuses. */
+class PruneCacheWorker(
+    appContext: Context,
+    workerParams: WorkerParameters,
+    private val appDatabase: AppDatabase,
+    private val accountManager: AccountManager
+) : CoroutineWorker(appContext, workerParams) {
+    override suspend fun doWork(): Result {
+        for (account in accountManager.accounts) {
+            Log.d(TAG, "Pruning database using account ID: ${account.id}")
+            appDatabase.timelineDao().cleanup(account.id, MAX_STATUSES_IN_CACHE)
+        }
+        return Result.success()
+    }
+
+    companion object {
+        private const val TAG = "PruneCacheWorker"
+        private const val MAX_STATUSES_IN_CACHE = 1000
+        const val PERIODIC_WORK_TAG = "PruneCacheWorker_periodic"
+    }
+
+    class Factory @Inject constructor(
+        private val appDatabase: AppDatabase,
+        private val accountManager: AccountManager
+    ) : ChildWorkerFactory {
+        override fun createWorker(appContext: Context, params: WorkerParameters): ListenableWorker {
+            return PruneCacheWorker(appContext, params, appDatabase, accountManager)
+        }
+    }
+}

app/src/main/java/com/keylesspalace/tusky/worker/WorkerFactory.kt

@@ -0,0 +1,56 @@
+/*
+ * Copyright 2023 Tusky Contributors
+ *
+ * This file is a part of Tusky.
+ *
+ * This program is free software; you can redistribute it and/or modify it under the terms of the
+ * GNU 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 General
+ * Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along with Tusky; if not,
+ * see <http://www.gnu.org/licenses>.
+ */
+
+package com.keylesspalace.tusky.worker
+
+import android.content.Context
+import androidx.work.ListenableWorker
+import androidx.work.WorkerFactory
+import androidx.work.WorkerParameters
+import javax.inject.Inject
+import javax.inject.Provider
+
+/**
+ * Workers implement this and are added to the map in [com.keylesspalace.tusky.di.WorkerModule]
+ * so they can be created by [WorkerFactory.createWorker].
+ */
+interface ChildWorkerFactory {
+    /** Create a new instance of the given worker. */
+    fun createWorker(appContext: Context, params: WorkerParameters): ListenableWorker
+}
+
+/**
+ * Creates workers, delegating to each worker's [ChildWorkerFactory.createWorker] to do the
+ * creation.
+ *
+ * @see [com.keylesspalace.tusky.components.notifications.NotificationWorker]
+ */
+class WorkerFactory @Inject constructor(
+    val workerFactories: Map<Class<out ListenableWorker>, @JvmSuppressWildcards Provider<ChildWorkerFactory>>
+) : WorkerFactory() {
+    override fun createWorker(
+        appContext: Context,
+        workerClassName: String,
+        workerParameters: WorkerParameters
+    ): ListenableWorker? {
+        val key = Class.forName(workerClassName)
+        workerFactories[key]?.let {
+            return it.get().createWorker(appContext, workerParameters)
+        }
+        return null
+    }
+}