from django.conf import settings
from django.core.cache import cache
from django.utils.translation import gettext_lazy as _

from ..models import OTPCode
from .sms import SMSError, get_sms_backend


class OTPCooldownError(Exception):
    def __init__(self, retry_after: int):
        self.retry_after = retry_after
        super().__init__(f"Wait {retry_after} seconds before requesting another code")


class OTPVerificationError(Exception):
    pass


def _cooldown_key(phone: str) -> str:
    return f"otp:cooldown:{phone}"


def send_otp(phone_number: str) -> OTPCode:
    cooldown = getattr(settings, "OTP_SEND_COOLDOWN_SECONDS", 60)
    if cache.get(_cooldown_key(phone_number)):
        raise OTPCooldownError(retry_after=cooldown)

    ttl_seconds = getattr(settings, "OTP_TTL_SECONDS", 120)
    length = getattr(settings, "OTP_CODE_LENGTH", 4)

    otp = OTPCode.issue(phone_number=phone_number, ttl_seconds=ttl_seconds, length=length)

    try:
        get_sms_backend().send_otp(phone_number, otp.code)
    except SMSError:
        otp.delete()
        raise

    cache.set(_cooldown_key(phone_number), "1", timeout=cooldown)
    return otp


def verify_otp(phone_number: str, code: str) -> OTPCode:
    otp = (
        OTPCode.objects.filter(phone_number=phone_number, is_used=False)
        .order_by("-created_at")
        .first()
    )
    if otp is None:
        raise OTPVerificationError(_("No active code for this phone number"))
    if otp.is_expired:
        raise OTPVerificationError(_("Code has expired"))
    if otp.attempts >= OTPCode.MAX_ATTEMPTS:
        raise OTPVerificationError(_("Too many attempts; request a new code"))

    if otp.code != str(code):
        OTPCode.objects.filter(pk=otp.pk).update(attempts=otp.attempts + 1)
        raise OTPVerificationError(_("Invalid code"))

    otp.mark_consumed()
    return otp