first cut of out of stock event [domain_event]

hjwp · hjwp · commit 63130e79d96b · 2019-07-18T22:12:32.000+01:00
diff --git a/src/allocation/events.py b/src/allocation/events.py
@@ -0,0 +1,9 @@
+from dataclasses import dataclass
+
+class Event:
+    pass
+
+@dataclass
+class OutOfStock(Event):
+    sku: str
+
diff --git a/src/allocation/model.py b/src/allocation/model.py
@@ -2,7 +2,7 @@
 from dataclasses import dataclass
 from datetime import date
 from typing import Optional, List, Set
-from allocation import exceptions
+from allocation import events
 
 
 class Product:
@@ -11,6 +11,7 @@ def __init__(self, sku: str, batches: List[Batch], version_number: int = 0):
         self.sku = sku
         self.batches = batches
         self.version_number = version_number
+        self.events = []  # type: List[events.Event]
 
     def allocate(self, line: OrderLine) -> str:
         try:
@@ -21,7 +22,9 @@ def allocate(self, line: OrderLine) -> str:
             self.version_number += 1
             return batch.reference
         except StopIteration:
-            raise exceptions.OutOfStock(f'Out of stock for sku {line.sku}')
+            self.events.append(events.OutOfStock(line.sku))
+            # raise exceptions.OutOfStock(f'Out of stock for sku {line.sku}')
+            return None
 
 
 @dataclass(unsafe_hash=True)
diff --git a/tests/unit/test_product.py b/tests/unit/test_product.py
@@ -1,6 +1,6 @@
 from datetime import date, timedelta
 import pytest
-from allocation import exceptions
+from allocation import events, exceptions
 from allocation.model import Product, OrderLine, Batch
 
 today = date.today()
@@ -51,6 +51,16 @@ def test_raises_out_of_stock_exception_if_cannot_allocate():
         product.allocate(different_sku_line)
 
 
+def test_records_out_of_stock_event_if_cannot_allocate():
+    sku1_batch = Batch('batch1', 'sku1', 100, eta=today)
+    sku2_line = OrderLine('oref', 'sku2', 10)
+    product = Product(sku='sku1', batches=[sku1_batch])
+
+    with pytest.raises(exceptions.OutOfStock):
+        product.allocate(sku2_line)
+    assert product.events[-1] == events.OutOfStock(sku='sku2')
+
+
 def test_increments_version_number():
     line = OrderLine('oref', "SCANDI-PEN", 10)
     product = Product(sku="SCANDI-PEN", batches=[Batch('b1', "SCANDI-PEN", 100, eta=None)])
