Revert of Dashboard - Remove pre-hook logic from alert.py.

dashboard/dashboard/models/alert.py

Index: dashboard/dashboard/models/alert.py
diff --git a/dashboard/dashboard/models/alert.py b/dashboard/dashboard/models/alert.py
index 91c11f282b4d283bd3e38dfe93164813361a2dc0..8e73f782fe035ebcbe15fa2b845a705fbe3fb9fb 100644
--- a/dashboard/dashboard/models/alert.py
+++ b/dashboard/dashboard/models/alert.py
@@ -41,6 +41,88 @@
   # kind=alert_group.AlertGroup can be added.
   group = ndb.KeyProperty(indexed=True)
 
+  def _pre_put_hook(self):
+    """Updates the alert's group."""
+    # TODO(qyearsley): Extract sub-methods from this method in order
+    # to make it shorter.
+
+    # The group should not be updated if this is the first time that the
+    # the Alert is being put. (If the key is auto-assigned, then key.id()
+    # will be None the first time.)
+    if not self.key.id():
+      return
+
+    # The previous state of this alert. (If this is the first time the
+    # alert is being put, then this will be None.
+    original_alert = self.key.get(use_cache=False)
+    if original_alert is None:
+      return
+
+    # If the alert does not have a group, don't do anything.
+    if not self.group:
+      return
+    # If the group key is "AnomalyGroup" (the previous incarnation of
+    # AlertGroup), we can just leave it as is. This will only apply to
+    # already-existing Anomaly entities, not new Anomaly entities.
+    if self.group.kind() != 'AlertGroup':
+      self.group = None
+      return
+    group = self.group.get()
+    if not group:
+      return
+
+    # Each AlertGroup should only be associated with entities of one class;
+    # i.e. an Anomaly entity shouldn't be grouped with a StoppageAlert entity.
+    alert_class = self.__class__
+
+    # When the bug ID changes, this alert may be updated to belong
+    # to the new group.
+    if self.bug_id != original_alert.bug_id:
+      grouped_alerts = alert_class.query(
+          alert_class.group == group.key).fetch()
+      grouped_alerts.append(self)
+
+      # The alert has been assigned a real bug ID.
+      # Update the group bug ID if necessary.
+      if self.bug_id > 0 and group.bug_id != self.bug_id:
+        group.bug_id = self.bug_id
+        group.put()
+
+      # The bug has been marked invalid/ignored. Kick it out of the group.
+      elif self.bug_id < 0 and self.bug_id is not None:
+        self._RemoveFromGroup(grouped_alerts)
+        grouped_alerts.remove(self)
+
+      # The bug has been un-triaged. Update the group's bug ID if this is
+      # the only alert in the group.
+      elif self.bug_id is None and len(grouped_alerts) == 1:
+        group.bug_id = None
+        group.put()
+
+      # Check and update the group's revision range if necessary.
+      group.UpdateRevisionRange(grouped_alerts)
+
+    elif (self.end_revision != original_alert.end_revision or
+          self.start_revision != original_alert.start_revision):
+      grouped_alerts = alert_class.query(alert_class.group == group.key).fetch()
+      grouped_alerts.append(self)
+      group.UpdateRevisionRange(grouped_alerts)
+
+  def _RemoveFromGroup(self, grouped_alerts):
+    """Removes an alert from its group and updates the group's properties.
+
+    Args:
+      grouped_alerts: The list of alerts in |group| used to calculate
+          new revision range; none are modified.
+    """
+    group = self.group.get()
+    self.group = None
+    grouped_alerts.remove(self)
+    if not grouped_alerts:
+      group.key.delete()
+      return
+    # Update minimum revision range for group.
+    group.UpdateRevisionRange(grouped_alerts)
 
   def GetTestMetadataKey(self):
     """Get the key for the TestMetadata entity of this alert.