Commit decrease item quantity in shopcart

service/routes.py

@@ -392,6 +392,53 @@
     return jsonify(item.serialize()), status.HTTP_200_OK
 
 
+######################################################################
+# DECREASE ITEM IN A SHOPCART
+######################################################################
+
+
+@app.route(
+    "/shopcarts/<int:shopcart_id>/items/<int:item_id>/decrement", methods=["PUT"]
+)
+def decrement_item_quantity(shopcart_id, item_id):
+    """
+    Decrement the quantity of an item in a Shopcart
+
+    This endpoint will decrement the quantity of an item in a Shopcart based the body that is posted
+    """
+
+    app.logger.info(
+        "Request to decrement the quantity of item with id %d in a shopcart with id: %d",
+        item_id,
+        shopcart_id,
+    )
+
+    shopcart = Shopcart.find(shopcart_id)
+    if not shopcart:
+        error(
+            status.HTTP_404_NOT_FOUND,
+            f"Shopcart with id: '{shopcart_id}' was not found.",
+        )
+
+    item = Item.find(item_id)
+
+    if not item:
+        error(
+            status.HTTP_404_NOT_FOUND,
+            f"Item with id: '{item_id}' was not found in shopcart with id: '{shopcart_id}'",
+        )
+
+    item._quantity -= 1
+
+    item.update()
+
+    app.logger.info(
+        "Item with id %d in shopcart with id %d updated.", item_id, shopcart_id
+    )
+
+    return jsonify(item.serialize()), status.HTTP_200_OK
+
+
 ######################################################################
 #  U T I L I T Y   F U N C T I O N S
 ######################################################################

tests/test_routes.py

@@ -382,6 +382,41 @@ def test_increment_quantity_by_one(self):
         )
         self.assertEqual(resp.status_code, status.HTTP_404_NOT_FOUND)
 
+    def test_decrement_quantity_by_one(self):
+        """It should decrement quantity by one"""
+        # add four items to the shopcart
+        shopcart = ShopcartFactory()
+        shopcart.create()
+        item = ItemFactory(shopcart=shopcart)
+        item.create()
+        # let's commit the newly created item to the DB
+        initial_quantity = item.quantity
+        resp = self.client.post(
+            f"{BASE_URL}/{shopcart.id}/items", json=item.serialize()
+        )
+        self.assertEqual(resp.status_code, status.HTTP_201_CREATED)
+
+        # let's get the item
+        resp = self.client.get(f"{BASE_URL}/{shopcart.id}/items")
+        self.assertEqual(resp.status_code, status.HTTP_200_OK)
+
+        resp = self.client.put(
+            f"{BASE_URL}/{shopcart.id}/items/{item.id}/decrement", json=item.serialize()
+        )
+        new_quantity = item.quantity
+        self.assertEqual(new_quantity, initial_quantity - 1)
+        self.assertEqual(resp.status_code, status.HTTP_200_OK)
+
+        resp = self.client.put(
+            f"{BASE_URL}/-1/items/{item.id}/decrement", json=item.serialize()
+        )
+        self.assertEqual(resp.status_code, status.HTTP_404_NOT_FOUND)
+
+        resp = self.client.put(
+            f"{BASE_URL}/{shopcart.id}/items/-1/decrement", json=item.serialize()
+        )
+        self.assertEqual(resp.status_code, status.HTTP_404_NOT_FOUND)
+
 
 ######################################################################
 #  T E S T   S A D   P A T H S