Validate that a given campaign config doesn't have 2 iterations starting on the same day.

Author: acerathereinspirative-nhs-nvir

src/eligibility_signposting_api/model/rules.py

@@ -1,13 +1,14 @@
 from __future__ import annotations
 
 import typing
+from collections import Counter
 from datetime import UTC, date, datetime
 from enum import StrEnum
 from functools import cached_property
 from operator import attrgetter
 from typing import Literal, NewType
 
-from pydantic import BaseModel, Field, field_serializer, field_validator
+from pydantic import BaseModel, Field, field_serializer, field_validator, model_validator
 
 if typing.TYPE_CHECKING:  # pragma: no cover
     from pydantic import SerializationInfo
@@ -162,6 +163,15 @@ def parse_dates(cls, v: str | date) -> date:
     def serialize_dates(v: date, _info: SerializationInfo) -> str:
         return v.strftime("%Y%m%d")
 
+    @model_validator(mode="after")
+    def check_no_overlapping_iterations(self) -> typing.Self:
+        iterations_by_date = Counter([i.iteration_date for i in self.iterations])
+        if multiple_found := next(((d, c) for d, c in iterations_by_date.most_common() if c > 1), None):
+            iteration_date, count = multiple_found
+            message = f"{count} iterations with iteration date {iteration_date} in campaign {self.id}"
+            raise ValueError(message)
+        return self
+
     @cached_property
     def campaign_live(self) -> bool:
         today = datetime.now(tz=UTC).date()

tests/unit/model/__init__.py

@@ -0,0 +1,19 @@
+import pytest
+from faker import Faker
+
+from tests.fixtures.builders.model.rule import CampaignConfigFactory, IterationFactory
+
+
+def test_iteration_with_overlapping_start_dates_not_allowed(faker: Faker):
+    # Given
+    iteration_date = faker.date("%Y%m%d")
+    iteration1 = IterationFactory.build(iteration_date=iteration_date)
+    iteration2 = IterationFactory.build(iteration_date=iteration_date)
+
+    # When, Then
+    with pytest.raises(
+        ValueError,
+        match=r"1 validation error for CampaignConfig\n"
+        r".*2 iterations with iteration date",
+    ):
+        CampaignConfigFactory.build(iterations=[iteration1, iteration2])