[#340] Alarm integration improvements.

- Emit `EntityDeleteEvent` when an alarm is expired and removed so
  clients can properly synchronize their state.

- `croniter.get_next()` should be timezone-aware.

platypush/plugins/alarm/__init__.py

@@ -3,11 +3,12 @@ import sys
 from threading import RLock
 from typing import Collection, Generator, Optional, Dict, Any, List, Union
 
-from sqlalchemy.orm import Session
+from sqlalchemy.orm import Session, make_transient
 
 from platypush.context import get_plugin
 from platypush.entities import EntityManager
-from platypush.entities.alarm import Alarm as AlarmTable
+from platypush.entities.alarm import Alarm as DbAlarm
+from platypush.message.event.entities import EntityDeleteEvent
 from platypush.plugins import RunnablePlugin, action
 from platypush.plugins.db import DbPlugin
 from platypush.plugins.media import MediaPlugin
@@ -141,7 +142,7 @@ class AlarmPlugin(RunnablePlugin, EntityManager):
         with self._db_lock, self._db.get_session() as session:
             yield session
 
-    def _merge_alarms(self, alarms: Dict[str, AlarmTable], session: Session):
+    def _merge_alarms(self, alarms: Dict[str, DbAlarm], session: Session):
         for name, alarm in alarms.items():
             if name in self.alarms:
                 existing_alarm = self.alarms[name]
@@ -154,7 +155,7 @@ class AlarmPlugin(RunnablePlugin, EntityManager):
                 # If the alarm record on the db is static, but the alarm is no
                 # longer present in the configuration, then we want to delete it
                 if alarm.static:
-                    session.delete(alarm)
+                    self._clear_alarm(alarm, session)
                 else:
                     self.alarms[name] = Alarm.from_db(
                         alarm,
@@ -165,7 +166,7 @@ class AlarmPlugin(RunnablePlugin, EntityManager):
     def _sync_alarms(self):
         with self._get_session() as session:
             db_alarms = {
-                str(alarm.name): alarm for alarm in session.query(AlarmTable).all()
+                str(alarm.name): alarm for alarm in session.query(DbAlarm).all()
             }
 
             self._merge_alarms(db_alarms, session)
@@ -178,6 +179,12 @@ class AlarmPlugin(RunnablePlugin, EntityManager):
             self.publish_entities(self.alarms.values())
             self._synced = True
 
+    def _clear_alarm(self, alarm: DbAlarm, session: Session):
+        self.alarms.pop(str(alarm.name), None)
+        session.delete(alarm)
+        make_transient(alarm)
+        self._bus.post(EntityDeleteEvent(entity=alarm))
+
     def _clear_expired_alarms(self, session: Session):
         expired_alarms = [
             alarm
@@ -188,17 +195,12 @@ class AlarmPlugin(RunnablePlugin, EntityManager):
         if not expired_alarms:
             return
 
-        expired_alarm_records = session.query(AlarmTable).filter(
-            AlarmTable.name.in_([alarm.name for alarm in expired_alarms])
+        expired_alarm_records = session.query(DbAlarm).filter(
+            DbAlarm.name.in_([alarm.name for alarm in expired_alarms])
         )
 
-        for alarm in expired_alarms:
-            self.alarms.pop(alarm.name, None)
-            if alarm.static:
-                continue
-
         for alarm in expired_alarm_records:
-            session.delete(alarm)
+            self._clear_alarm(alarm, session)
 
     def _get_alarms(self) -> List[Alarm]:
         return sorted(
@@ -407,7 +409,7 @@ class AlarmPlugin(RunnablePlugin, EntityManager):
         self.publish_entities(self.alarms.values())
         return ret
 
-    def transform_entities(self, entities: Collection[Alarm], **_) -> List[AlarmTable]:
+    def transform_entities(self, entities: Collection[Alarm], **_) -> List[DbAlarm]:
         return [alarm.to_db() for alarm in entities]
 
     def main(self):

platypush/plugins/alarm/_model.py

@@ -6,9 +6,10 @@ import threading
 from typing import Callable, Optional, Union
 
 import croniter
+from dateutil.tz import gettz
 
 from platypush.context import get_bus, get_plugin
-from platypush.entities.alarm import Alarm as AlarmTable
+from platypush.entities.alarm import Alarm as AlarmDb
 from platypush.message.request import Request
 from platypush.message.event.alarm import (
     AlarmStartedEvent,
@@ -111,7 +112,10 @@ class Alarm:
 
             try:
                 # If when is a cron expression, get the next run time
-                t = croniter.croniter(self.when, now).get_next()
+                t = croniter.croniter(
+                    self.when,
+                    datetime.datetime.fromtimestamp(now).replace(tzinfo=gettz()),
+                ).get_next()
             except (AttributeError, croniter.CroniterBadCronError):
                 try:
                     # If when is an ISO-8601 timestamp, parse it
@@ -268,7 +272,7 @@ class Alarm:
         }
 
     @classmethod
-    def from_db(cls, alarm: AlarmTable, **kwargs) -> 'Alarm':
+    def from_db(cls, alarm: AlarmDb, **kwargs) -> 'Alarm':
         return cls(
             when=str(alarm.when),
             name=str(alarm.name),
@@ -282,8 +286,8 @@ class Alarm:
             **kwargs,
         )
 
-    def to_db(self) -> AlarmTable:
-        return AlarmTable(
+    def to_db(self) -> AlarmDb:
+        return AlarmDb(
             id=self.name,
             name=self.name,
             when=self.when,