from __future__ import annotations

from contextlib import AbstractContextManager
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"]):
    """Simple unit-of-work wrapper around SQLAlchemy sessions."""

    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._scenario_validator = ScenarioComparisonValidator()
        return self

    def __exit__(self, exc_type, exc_value, traceback) -> None:
        assert self.session is not None
        if exc_type is None:
            self.session.commit()
        else:
            self.session.rollback()
        self.session.close()
        self._scenario_validator = None

    def flush(self) -> None:
        if not self.session:
            raise RuntimeError("UnitOfWork session is not initialised")
        self.session.flush()

    def commit(self) -> None:
        if not self.session:
            raise RuntimeError("UnitOfWork session is not initialised")
        self.session.commit()

    def rollback(self) -> None:
        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)