first cut of out of stock event [domain_event]

hjwp · hjwp · commit 418914626573 · 2024-03-01T15:01:35.000Z
diff --git a/src/allocation/domain/events.py b/src/allocation/domain/events.py
@@ -0,0 +1,10 @@
+from dataclasses import dataclass
+
+
+class Event:
+    pass
+
+
+@dataclass
+class OutOfStock(Event):
+    sku: str
diff --git a/src/allocation/domain/model.py b/src/allocation/domain/model.py
@@ -2,6 +2,7 @@
 from dataclasses import dataclass
 from datetime import date
 from typing import Optional, List, Set
+from . import events
 
 
 class OutOfStock(Exception):
@@ -13,6 +14,7 @@ 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 +23,9 @@ def allocate(self, line: OrderLine) -> str:
             self.version_number += 1
             return batch.reference
         except StopIteration:
-            raise OutOfStock(f"Out of stock for sku {line.sku}")
+            self.events.append(events.OutOfStock(line.sku))
+            # raise 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
@@ -1,5 +1,7 @@
 from datetime import date, timedelta
 import pytest
+
+from allocation.domain import events
 from allocation.domain.model import Product, OrderLine, Batch, OutOfStock
 
 today = date.today()
@@ -51,6 +53,16 @@ def test_raises_out_of_stock_exception_if_cannot_allocate():
         product.allocate(OrderLine("order2", "SMALL-FORK", 1))
 
 
+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(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(
