Add some utility classes for issuing LVAlerts

gracedb/alerts/utils.py

+# Utilities for issuing alerts
+
+class AlertIssuer(object):
+    """Base class for issuing XMPP alerts"""
+    serializer_class = None
+    alert_types = None
+
+    def __init__(self, obj, alert_type, *args, **kwargs):
+        # Check alert type
+        if alert_type not in self.alert_types:
+            raise ValueError('alert_type should be in {0}'.format(
+                self.alert_types))
+
+        # Assign attributes
+        self.obj = obj
+        self.alert_type = alert_type
+
+    def serialize_obj(self):
+        return self.serializer_class(self.obj).data
+
+    def issue_alerts(self):
+        # Should be overridden in derived classes
+        return NotImplemented
+
+
+class AlertIssuerWithParentObject(AlertIssuer):
+    """
+    Base class for issuing XMPP alerts. Handles the case where
+    we want to include both a serialized object (like a log, label, etc.),
+    as well as a "parent" object to which the first object is attched, like
+    an event or superevent.
+    """
+    parent_serializer_class = None
+
+    def serialize_parent(self):
+        return self.serializer_class(self.get_parent_obj())
+
+    def get_parent_obj(self):
+        if not hasattr(self, 'parent_obj'):
+            self.parent_obj = self._get_parent_obj()
+        return self.parent_obj
+
+    def _get_parent_obj(self):
+        return NotImplemented