first cut of message bus [service_talks_to_messagebus]

hjwp · hjwp · commit c0359874eabd · 2019-07-18T22:23:22.000+01:00
diff --git a/src/allocation/messagebus.py b/src/allocation/messagebus.py
@@ -0,0 +1,23 @@
+from typing import List, Dict, Callable, Type
+from allocation import email, events
+
+
+def handle(events_: List[events.Event]):
+    while events_:
+        event = events_.pop(0)
+        for handler in HANDLERS[type(event)]:
+            handler(event)
+
+
+def send_out_of_stock_notification(event: events.OutOfStock):
+    email.send_mail(
+        'stock@made.com',
+        f'Out of stock for {event.sku}',
+    )
+
+
+HANDLERS = {
+    events.OutOfStock: [send_out_of_stock_notification],
+
+}  # type: Dict[Type[events.Event], List[Callable]]
+
diff --git a/src/allocation/services.py b/src/allocation/services.py
@@ -2,7 +2,7 @@
 from typing import Optional
 from datetime import date
 
-from allocation import email, exceptions, model, unit_of_work
+from allocation import exceptions, messagebus, model, unit_of_work
 from allocation.model import OrderLine
 
 
@@ -32,6 +32,5 @@ def allocate(
             batchref = product.allocate(line)
             uow.commit()
             return batchref
-        except exceptions.OutOfStock:
-            email.send_mail('stock@made.com', f'Out of stock for {line.sku}')
-            raise
+        finally:
+            messagebus.handle(product.events)
