Implement Stories feature behind flag.

Co-Authored-By: Greyson Parrelli <37311915+greyson-signal@users.noreply.github.com>
Co-Authored-By: Rashad Sookram <95182499+rashad-signal@users.noreply.github.com>

app/src/main/java/org/thoughtcrime/securesms/service/ExpiringStoriesManager.kt

@@ -0,0 +1,71 @@
+package org.thoughtcrime.securesms.service
+
+import android.app.Application
+import android.content.BroadcastReceiver
+import android.content.Context
+import android.content.Intent
+import androidx.annotation.WorkerThread
+import org.signal.core.util.logging.Log
+import org.thoughtcrime.securesms.database.SignalDatabase
+import org.thoughtcrime.securesms.dependencies.ApplicationDependencies
+import java.util.concurrent.TimeUnit
+
+/**
+ * Manages deleting stories 24 hours after they've been sent.
+ */
+class ExpiringStoriesManager(
+  application: Application
+) : TimedEventManager<ExpiringStoriesManager.Event>(application, "ExpiringStoriesManager") {
+
+  companion object {
+    private val TAG = Log.tag(ExpiringStoriesManager::class.java)
+
+    private val STORY_LIFESPAN = TimeUnit.HOURS.toMillis(24)
+  }
+
+  private val mmsDatabase = SignalDatabase.mms
+
+  init {
+    scheduleIfNecessary()
+  }
+
+  @WorkerThread
+  override fun getNextClosestEvent(): Event? {
+    val oldestTimestamp = mmsDatabase.oldestStorySendTimestamp ?: return null
+
+    val timeSinceSend = System.currentTimeMillis() - oldestTimestamp
+    val delay = (STORY_LIFESPAN - timeSinceSend).coerceAtLeast(0)
+    Log.i(TAG, "The oldest story needs to be deleted in $delay ms.")
+
+    return Event(delay)
+  }
+
+  @WorkerThread
+  override fun executeEvent(event: Event) {
+    val threshold = System.currentTimeMillis() - STORY_LIFESPAN
+    val deletes = mmsDatabase.deleteStoriesOlderThan(threshold)
+    Log.i(TAG, "Deleted $deletes stories before $threshold")
+  }
+
+  @WorkerThread
+  override fun getDelayForEvent(event: Event): Long = event.delay
+
+  @WorkerThread
+  override fun scheduleAlarm(application: Application, delay: Long) {
+    setAlarm(application, delay, ExpireStoriesAlarm::class.java)
+  }
+
+  data class Event(val delay: Long)
+
+  class ExpireStoriesAlarm : BroadcastReceiver() {
+
+    companion object {
+      private val TAG = Log.tag(ExpireStoriesAlarm::class.java)
+    }
+
+    override fun onReceive(context: Context?, intent: Intent?) {
+      Log.d(TAG, "onReceive()")
+      ApplicationDependencies.getExpireStoriesManager().scheduleIfNecessary()
+    }
+  }
+}