feat: implement scenario comparison validation and API endpoint with comprehensive unit tests

services/unit_of_work.py

@@ -1,17 +1,19 @@
 from __future__ import annotations
 
 from contextlib import AbstractContextManager
-from typing import Callable
+from typing import Callable, Sequence
 
 from sqlalchemy.orm import Session
 
 from config.database import SessionLocal
+from models import Scenario
 from services.repositories import (
     FinancialInputRepository,
     ProjectRepository,
     ScenarioRepository,
     SimulationParameterRepository,
 )
+from services.scenario_validation import ScenarioComparisonValidator
 
 
 class UnitOfWork(AbstractContextManager["UnitOfWork"]):
@@ -20,13 +22,16 @@ class UnitOfWork(AbstractContextManager["UnitOfWork"]):
     def __init__(self, session_factory: Callable[[], Session] = SessionLocal) -> None:
         self._session_factory = session_factory
         self.session: Session | None = None
+        self._scenario_validator: ScenarioComparisonValidator | None = None
 
     def __enter__(self) -> "UnitOfWork":
         self.session = self._session_factory()
         self.projects = ProjectRepository(self.session)
         self.scenarios = ScenarioRepository(self.session)
         self.financial_inputs = FinancialInputRepository(self.session)
-        self.simulation_parameters = SimulationParameterRepository(self.session)
+        self.simulation_parameters = SimulationParameterRepository(
+            self.session)
+        self._scenario_validator = ScenarioComparisonValidator()
         return self
 
     def __exit__(self, exc_type, exc_value, traceback) -> None:
@@ -36,6 +41,7 @@ class UnitOfWork(AbstractContextManager["UnitOfWork"]):
         else:
             self.session.rollback()
         self.session.close()
+        self._scenario_validator = None
 
     def flush(self) -> None:
         if not self.session:
@@ -51,3 +57,21 @@ class UnitOfWork(AbstractContextManager["UnitOfWork"]):
         if not self.session:
             raise RuntimeError("UnitOfWork session is not initialised")
         self.session.rollback()
+
+    def validate_scenarios_for_comparison(
+        self, scenario_ids: Sequence[int]
+    ) -> list[Scenario]:
+        if not self.session or not self._scenario_validator:
+            raise RuntimeError("UnitOfWork session is not initialised")
+
+        scenarios = [self.scenarios.get(scenario_id)
+                     for scenario_id in scenario_ids]
+        self._scenario_validator.validate(scenarios)
+        return scenarios
+
+    def validate_scenario_models_for_comparison(
+        self, scenarios: Sequence[Scenario]
+    ) -> None:
+        if not self._scenario_validator:
+            raise RuntimeError("UnitOfWork session is not initialised")
+        self._scenario_validator.validate(scenarios)