Add support for scheduled message sends.

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

@@ -0,0 +1,78 @@
+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 org.thoughtcrime.securesms.jobs.IndividualSendJob
+import org.thoughtcrime.securesms.jobs.PushGroupSendJob
+
+/**
+ * Manages waking up and sending scheduled messages at the correct time
+ */
+class ScheduledMessageManager(
+  val application: Application
+) : TimedEventManager<ScheduledMessageManager.Event>(application, "ScheduledMessagesManager") {
+
+  companion object {
+    private val TAG = Log.tag(ScheduledMessageManager::class.java)
+  }
+
+  private val messagesTable = SignalDatabase.messages
+
+  init {
+    scheduleIfNecessary()
+  }
+
+  @WorkerThread
+  override fun getNextClosestEvent(): Event? {
+    val oldestTimestamp = messagesTable.oldestScheduledSendTimestamp ?: return null
+
+    val delay = (oldestTimestamp - System.currentTimeMillis()).coerceAtLeast(0)
+    Log.i(TAG, "The next scheduled message needs to be sent in $delay ms.")
+
+    return Event(delay)
+  }
+
+  @WorkerThread
+  override fun executeEvent(event: Event) {
+    val scheduledMessagesToSend = messagesTable.getScheduledMessagesBefore(System.currentTimeMillis())
+    for (record in scheduledMessagesToSend) {
+      if (SignalDatabase.messages.clearScheduledStatus(record.threadId, record.id)) {
+        if (record.recipient.isPushGroup) {
+          PushGroupSendJob.enqueue(application, ApplicationDependencies.getJobManager(), record.id, record.recipient.id, emptySet())
+        } else {
+          IndividualSendJob.enqueue(application, ApplicationDependencies.getJobManager(), record.id, record.recipient)
+        }
+      } else {
+        Log.i(TAG, "messageId=${record.id} was not a scheduled message, ignoring")
+      }
+    }
+  }
+
+  @WorkerThread
+  override fun getDelayForEvent(event: Event): Long = event.delay
+
+  @WorkerThread
+  override fun scheduleAlarm(application: Application, delay: Long) {
+    trySetExactAlarm(application, System.currentTimeMillis() + delay, ScheduledMessagesAlarm::class.java)
+  }
+
+  data class Event(val delay: Long)
+
+  class ScheduledMessagesAlarm : BroadcastReceiver() {
+
+    companion object {
+      private val TAG = Log.tag(ScheduledMessagesAlarm::class.java)
+    }
+
+    override fun onReceive(context: Context?, intent: Intent?) {
+      Log.d(TAG, "onReceive()")
+      ApplicationDependencies.getScheduledMessageManager().scheduleIfNecessary()
+    }
+  }
+}

app/src/main/java/org/thoughtcrime/securesms/service/TimedEventManager.java

@@ -5,6 +5,7 @@ import android.app.Application;
 import android.app.PendingIntent;
 import android.content.Context;
 import android.content.Intent;
+import android.os.Build;
 import android.os.Handler;
 import android.os.HandlerThread;
 
@@ -14,6 +15,7 @@ import androidx.annotation.Nullable;
 import androidx.annotation.WorkerThread;
 
 import org.signal.core.util.PendingIntentFlags;
+import org.signal.core.util.logging.Log;
 import org.thoughtcrime.securesms.util.ServiceUtil;
 
 /**
@@ -21,6 +23,8 @@ import org.thoughtcrime.securesms.util.ServiceUtil;
  */
 public abstract class TimedEventManager<E> {
 
+  private static final String TAG = Log.tag(TimedEventManager.class);
+
   private final Application application;
   private final Handler     handler;
 
@@ -91,4 +95,29 @@ public abstract class TimedEventManager<E> {
     alarmManager.cancel(pendingIntent);
     alarmManager.set(AlarmManager.RTC_WAKEUP, System.currentTimeMillis() + delay, pendingIntent);
   }
+
+  protected static void trySetExactAlarm(@NonNull Context context, long timestamp, @NonNull Class alarmClass) {
+    Intent        intent        = new Intent(context, alarmClass);
+    PendingIntent pendingIntent = PendingIntent.getBroadcast(context, 0, intent, PendingIntentFlags.mutable());
+    AlarmManager  alarmManager  = ServiceUtil.getAlarmManager(context);
+
+    alarmManager.cancel(pendingIntent);
+
+    boolean hasManagerPermission = Build.VERSION.SDK_INT < 31 || alarmManager.canScheduleExactAlarms();
+    if (hasManagerPermission) {
+      try {
+        if (Build.VERSION.SDK_INT >= 23) {
+          alarmManager.setExactAndAllowWhileIdle(AlarmManager.RTC_WAKEUP, timestamp, pendingIntent);
+        } else {
+          alarmManager.setExact(AlarmManager.RTC_WAKEUP, timestamp, pendingIntent);
+        }
+        return;
+      } catch (Exception e) {
+        Log.w(TAG, e);
+      }
+    }
+
+    Log.w(TAG, "Unable to schedule exact alarm, falling back to inexact alarm, scheduling alarm for: " + timestamp);
+    alarmManager.set(AlarmManager.RTC_WAKEUP, timestamp, pendingIntent);
+  }
 }