import json
from decimal import Decimal

from infrastructure.ai import prompts
from domain import CurrencyConverter, FinancialModel
from application.forecast import ForecastService


class AssistantError(Exception):
    pass


class _DecimalEncoder(json.JSONEncoder):
    """JSON-сериализатор: Decimal → str (для AI-промптов)."""

    def default(self, o):
        if isinstance(o, Decimal):
            return str(o)
        return super().default(o)


class AssistantService:
    def __init__(
        self,
        model: FinancialModel,
        converter: CurrencyConverter | None = None,
        display_currency: str | None = None,
    ):
        self.model = model
        self.converter = converter or CurrencyConverter(model.exchange_rates)
        self.display_currency = display_currency or model.base_currency

    def analyze(self, months: int = 12) -> dict:
        forecast_service = ForecastService(self.model)
        forecast_result = forecast_service.forecast_cashflow(months)
        summary = forecast_service.summary(months)

        prompt = prompts.format_context(
            model_json=json.dumps(self.model.to_dict(), indent=2, ensure_ascii=False, cls=_DecimalEncoder),
            forecast_json=json.dumps(forecast_result, indent=2, ensure_ascii=False, cls=_DecimalEncoder),
            months=months,
            base_currency=self.model.base_currency,
            display_currency=self.display_currency,
        )

        return {
            "prompt": prompt,
            "summary": summary,
            "forecast": forecast_result,
            "ai_response": None,
        }

    def advice(self, question: str, months: int = 12) -> dict:
        forecast_service = ForecastService(self.model)
        forecast_result = forecast_service.forecast_cashflow(months)

        prompt = prompts.ADVICE_PROMPT.format(
            model_json=json.dumps(self.model.to_dict(), indent=2, ensure_ascii=False, cls=_DecimalEncoder),
            forecast_json=json.dumps(forecast_result, indent=2, ensure_ascii=False, cls=_DecimalEncoder),
            question=question,
            base_currency=self.model.base_currency,
            display_currency=self.display_currency,
        )

        return {
            "prompt": prompt,
            "ai_response": None,
        }

    def compare_scenarios(self, scenarios_json: str) -> dict:
        prompt = prompts.SCENARIO_COMPARISON_PROMPT.format(
            scenarios_json=scenarios_json,
            base_currency=self.model.base_currency,
            display_currency=self.display_currency,
        )
        return {
            "prompt": prompt,
            "ai_response": None,
        }