from typing import Protocol

from app.repositories.protocols import IUserRepository


class IReferralPayloadParser(Protocol):
    """Parse Telegram deep-link payload (e.g. `ref_ABC123`) into internal referrer key."""

    def parse(self, raw: str | None) -> str | None: ...


class DefaultReferralPayloadParser:
    """Placeholder: expects `ref_<code>`; extend with signed tokens or DB lookup later."""

    PREFIX = "ref_"

    def parse(self, raw: str | None) -> str | None:
        if not raw:
            return None
        if raw.startswith(self.PREFIX):
            return raw[len(self.PREFIX) :].strip() or None
        return None


class ReferralService:
    """
    Resolves referral payloads to referrer user rows.
    Placeholder: code is treated as referrer's telegram_id string for demo wiring;
    replace with dedicated referral codes table or signed deep links in production.
    """

    def __init__(
        self,
        users: IUserRepository,
        parser: IReferralPayloadParser | None = None,
    ) -> None:
        self._users = users
        self._parser = parser or DefaultReferralPayloadParser()

    async def resolve_referrer_id(
        self,
        start_payload: str | None,
        *,
        invitee_telegram_id: int,
    ) -> int | None:
        code = self._parser.parse(start_payload)
        if not code:
            return None
        # Placeholder: interpret code as referrer's telegram_id (digits only).
        if not code.isdigit():
            return None
        referrer = await self._users.get_by_telegram_id(int(code))
        if referrer is None:
            return None
        if referrer.telegram_id == invitee_telegram_id:
            return None
        return referrer.id