from copy import deepcopy
from decimal import Decimal

from domain import FinancialModel, ForecastScenario
from application.forecast import ForecastService


class ScenarioError(Exception):
    pass


DEFAULT_SCENARIOS = {
    "baseline": ForecastScenario(
        name="baseline",
        income_multiplier=Decimal("1.0"),
        expense_multiplier=Decimal("1.0"),
        growth_multiplier=Decimal("1.0"),
        description="Базовый сценарий без изменений",
    ),
    "optimistic": ForecastScenario(
        name="optimistic",
        income_multiplier=Decimal("1.15"),
        expense_multiplier=Decimal("0.95"),
        growth_multiplier=Decimal("1.2"),
        description="Оптимистичный: доход +15%, расход -5%, рост активов +20%",
    ),
    "pessimistic": ForecastScenario(
        name="pessimistic",
        income_multiplier=Decimal("0.85"),
        expense_multiplier=Decimal("1.1"),
        growth_multiplier=Decimal("0.8"),
        description="Пессимистичный: доход -15%, расход +10%, рост активов -20%",
    ),
}


class ScenarioService:
    def __init__(self, model: FinancialModel):
        self.model = deepcopy(model)

    def apply(self, scenario: ForecastScenario, months: int = 12) -> dict:
        model = deepcopy(self.model)

        for t in model.transactions:
            if t.amount > 0:
                t.amount = t.amount * scenario.income_multiplier
            else:
                t.amount = t.amount * scenario.expense_multiplier

        for r in model.recurring:
            if r.category == "income":
                r.amount = r.amount * scenario.income_multiplier
            else:
                r.amount = r.amount * scenario.expense_multiplier

        for a in model.assets:
            a.growth_rate = a.growth_rate * scenario.growth_multiplier

        service = ForecastService(model)
        result = service.summary(months)
        result["scenario"] = scenario.name
        result["scenario_description"] = scenario.description
        return result

    def compare(self, months: int = 12) -> dict:
        results = {}
        for name, scenario in DEFAULT_SCENARIOS.items():
            results[name] = self.apply(scenario, months)
        return results

    def what_if(
        self,
        income_mult: Decimal | float = Decimal("1.0"),
        expense_mult: Decimal | float = Decimal("1.0"),
        growth_mult: Decimal | float = Decimal("1.0"),
        months: int = 12,
    ) -> dict:
        def to_d(v: Decimal | float) -> Decimal:
            return v if isinstance(v, Decimal) else Decimal(str(v))

        scenario = ForecastScenario(
            name="what-if",
            income_multiplier=to_d(income_mult),
            expense_multiplier=to_d(expense_mult),
            growth_multiplier=to_d(growth_mult),
            description=(
                f"What-if: income x{income_mult}, "
                f"expense x{expense_mult}, growth x{growth_mult}"
            ),
        )
        return self.apply(scenario, months)