"""OTP service."""

import secrets
from datetime import UTC, datetime, timedelta

from customer_portal.models.otp import OTPCode


class OTPService:
    """Generate and verify OTP codes."""

    OTP_LENGTH = 6
    OTP_LIFETIME_MINUTES = 10

    @staticmethod
    def generate() -> str:
        """Generate random 6-digit OTP."""
        return "".join(
            secrets.choice("0123456789") for _ in range(OTPService.OTP_LENGTH)
        )

    @staticmethod
    def create_for_customer(db_session, customer_id: int, purpose: str) -> str:
        """Create OTP for customer.

        Args:
            db_session: Database session
            customer_id: Customer ID
            purpose: OTP purpose (login, register, reset)

        Returns:
            Generated OTP code
        """
        # Invalidate any existing unused OTPs for same purpose
        db_session.query(OTPCode).filter(
            OTPCode.customer_id == customer_id,
            OTPCode.purpose == purpose,
            OTPCode.used_at.is_(None),
        ).update({"used_at": datetime.now(UTC)})

        code = OTPService.generate()
        expires_at = datetime.now(UTC) + timedelta(
            minutes=OTPService.OTP_LIFETIME_MINUTES
        )

        otp = OTPCode(
            customer_id=customer_id,
            code=code,
            purpose=purpose,
            expires_at=expires_at,
        )
        db_session.add(otp)
        db_session.commit()

        return code

    @staticmethod
    def verify(db_session, customer_id: int, code: str, purpose: str) -> bool:
        """Verify OTP code.

        Args:
            db_session: Database session
            customer_id: Customer ID
            code: OTP code to verify
            purpose: OTP purpose

        Returns:
            True if code is valid, False otherwise
        """
        otp = (
            db_session.query(OTPCode)
            .filter(
                OTPCode.customer_id == customer_id,
                OTPCode.code == code,
                OTPCode.purpose == purpose,
                OTPCode.used_at.is_(None),
                OTPCode.expires_at > datetime.now(UTC),
            )
            .first()
        )

        if otp:
            otp.used_at = datetime.now(UTC)
            db_session.commit()
            return True

        return False

    @staticmethod
    def count_recent_attempts(db_session, customer_id: int, minutes: int = 60) -> int:
        """Count recent OTP attempts for rate limiting.

        Args:
            db_session: Database session
            customer_id: Customer ID
            minutes: Time window in minutes

        Returns:
            Number of OTPs created in time window
        """
        since = datetime.now(UTC) - timedelta(minutes=minutes)
        return (
            db_session.query(OTPCode)
            .filter(
                OTPCode.customer_id == customer_id,
                OTPCode.created_at >= since,
            )
            .count()
        )