"""CDEK response mapper to unified delivery schema."""

from decimal import Decimal
from typing import Any

from app.schemas.response import DeliveryPrice


class CDEKMappingError(ValueError):
    """Raised when CDEK response cannot be mapped."""


def map_cdek_response(payload: dict[str, Any]) -> DeliveryPrice:
    tariff = _get_first_tariff(payload)

    service_name = tariff.get("tariff_name") or tariff.get("tariff_code")
    if service_name is None:
        raise CDEKMappingError("CDEK tariff_name is missing.")

    raw_price = tariff.get("delivery_sum")
    if raw_price is None:
        raise CDEKMappingError("CDEK delivery_sum is missing.")

    period_min = tariff.get("period_min")
    if period_min is None:
        raise CDEKMappingError("CDEK period_min is missing.")
    period_max = tariff.get("period_max", period_min)

    raw_currency = tariff.get("currency") or payload.get("currency") or "RUB"

    try:
        return DeliveryPrice(
            provider="cdek",
            service_name=str(service_name),
            price=Decimal(str(raw_price)),
            currency=str(raw_currency).upper(),
            delivery_days_min=int(period_min),
            delivery_days_max=int(period_max),
        )
    except (ArithmeticError, TypeError, ValueError) as exc:
        raise CDEKMappingError("CDEK response fields have invalid values.") from exc


def _get_first_tariff(payload: dict[str, Any]) -> dict[str, Any]:
    tariff_codes = payload.get("tariff_codes")
    if not isinstance(tariff_codes, list) or not tariff_codes:
        raise CDEKMappingError("CDEK response must include non-empty tariff_codes.")
    tariff = tariff_codes[0]
    if not isinstance(tariff, dict):
        raise CDEKMappingError("CDEK tariff entry must be an object.")
    return tariff