import random
import string
from datetime import timedelta

from django.contrib.auth import get_user_model, password_validation
from django.core.exceptions import ValidationError as DjangoValidationError
from django.db import transaction
from django.utils import timezone
from django_redis import get_redis_connection
from rest_framework.exceptions import ValidationError
from rest_framework_simplejwt.exceptions import TokenError
from rest_framework_simplejwt.tokens import RefreshToken

from apps.users.models import LoginAttempt
from apps.users.tasks import send_verification_sms
from apps.users.utils import record_login_attempt

User = get_user_model()

USER_ALREADY_EXISTS_MESSAGE = "User already exists."
PASSWORD_REUSE_MESSAGE = "رمز عبور جدید نباید با رمز عبور قبلی یکسان باشد."
OTP_EXPIRY_SECONDS = 120


def _validate_new_password(password, *, user, field_name):
    try:
        password_validation.validate_password(password, user=user)
    except DjangoValidationError as exc:
        raise ValidationError({field_name: exc.messages[0] if len(exc.messages) == 1 else exc.messages})


def get_tokens_for_user(user):
    """Helper service to generate JWT tokens."""
    refresh = RefreshToken.for_user(user)
    return {
        "access": str(refresh.access_token),
        "refresh": str(refresh),
    }


def register_user_with_password(mobile, password):
    """Business logic for registering a user with just a password."""
    user, created, restored = User.get_or_restore(mobile=mobile)

    if not created and not restored:
        raise ValidationError({"detail": USER_ALREADY_EXISTS_MESSAGE})

    user.set_password(password)
    user.save()

    return get_tokens_for_user(user)


@transaction.atomic
def register_user_with_otp(mobile, code, password, first_name="", last_name=""):
    """Business logic for verifying OTP and registering a user."""
    if User.objects.filter(mobile=mobile).exists():
        raise ValidationError({"mobile": "این شماره قبلاً ثبت شده است."})

    redis_conn = get_redis_connection("default")
    stored_code = redis_conn.get(f"verification_code:{mobile}")

    if not stored_code:
        raise ValidationError({"code": "کد تأیید یافت نشد."})
    if stored_code.decode("utf-8") != code:
        raise ValidationError({"code": "کد تأیید اشتباه است."})

    user = User.objects.create_user(
        mobile=mobile,
        password=password,
        first_name=first_name,
        last_name=last_name,
        is_verified=True,
        is_active=True,
    )

    redis_conn.delete(f"verification_code:{mobile}")

    return get_tokens_for_user(user)


def generate_and_send_otp(mobile, mode):
    """Business logic for generating OTP, checking existence rules, and sending SMS."""
    user_exists = User.objects.filter(mobile=mobile).exists()

    if mode == "register" and user_exists:
        raise ValidationError({"mobile": "این شماره قبلاً ثبت‌نام شده است."})

    if mode in ["login", "forget_password"] and not user_exists:
        raise ValidationError({"mobile": "این شماره یافت نشد."})

    verification_code = "".join(random.choices(string.digits, k=5))

    redis_conn = get_redis_connection("default")
    redis_conn.setex(f"verification_code:{mobile}", OTP_EXPIRY_SECONDS, verification_code)

    send_verification_sms.delay(mobile, verification_code)
    expires_at = timezone.now() + timedelta(seconds=OTP_EXPIRY_SECONDS)
    return {
        "detail": "OTP sent successfully",
        "expires_in_seconds": OTP_EXPIRY_SECONDS,
        "expires_at": expires_at.isoformat(),
    }


def login_with_password(mobile, password, request=None):
    """Authenticate user with password and record the attempt."""
    user = User.objects.filter(mobile=mobile).first()

    if not user or not user.check_password(password):
        record_login_attempt(request, user, LoginAttempt.StatusType.FAILED)
        raise ValidationError({"detail": "شماره موبایل یا رمز عبور اشتباه است."})

    if not user.is_active:
        raise ValidationError({"detail": "حساب کاربری شما غیرفعال شده است."})

    record_login_attempt(request, user, LoginAttempt.StatusType.SUCCESS)
    return get_tokens_for_user(user)


def login_with_otp(mobile, code, request=None):
    """Authenticate or implicitly register user via OTP."""
    redis_conn = get_redis_connection("default")
    stored_code = redis_conn.get(f"verification_code:{mobile}")

    if not stored_code or stored_code.decode("utf-8") != code:
        record_login_attempt(request, None, LoginAttempt.StatusType.FAILED)
        raise ValidationError({"code": "کد تایید نامعتبر است یا منقضی شده است."})

    user, created = User.objects.get_or_create(mobile=mobile)
    if created:
        user.set_unusable_password()
        user.save()

    if not user.is_active:
        raise ValidationError({"detail": "حساب کاربری شما غیرفعال شده است."})

    record_login_attempt(request, user, LoginAttempt.StatusType.SUCCESS)
    redis_conn.delete(f"verification_code:{mobile}")

    return get_tokens_for_user(user)


def reset_password_with_otp(mobile, code, password):
    """Verify OTP and change forgotten password."""
    user = User.objects.filter(mobile=mobile).first()
    if not user:
        raise ValidationError({"mobile": "کاربری با این شماره یافت نشد."})

    redis_conn = get_redis_connection("default")
    stored_code = redis_conn.get(f"verification_code:{mobile}")

    if not stored_code or stored_code.decode("utf-8") != code:
        raise ValidationError({"code": "کد تایید نامعتبر است یا منقضی شده است."})

    _validate_new_password(password, user=user, field_name="password")

    if user.check_password(password):
        raise ValidationError({"password": PASSWORD_REUSE_MESSAGE})

    user.set_password(password)
    user.save()

    redis_conn.delete(f"verification_code:{mobile}")


def change_password(user, old_password, new_password):
    """Change password for an already authenticated user."""
    if not user.check_password(old_password):
        raise ValidationError({"old_password": "رمز عبور فعلی اشتباه است."})

    _validate_new_password(new_password, user=user, field_name="new_password")

    if old_password == new_password:
        raise ValidationError({"new_password": PASSWORD_REUSE_MESSAGE})

    user.set_password(new_password)
    user.password_updated_at = timezone.now()
    user.save(update_fields=["password", "password_updated_at"])


def logout_user(refresh_token_str):
    """Blacklist the user's refresh token."""
    if not refresh_token_str:
        raise ValidationError({"refresh": "توکن رفرش الزامی است."})
    try:
        token = RefreshToken(refresh_token_str)
        token.blacklist()
    except TokenError:
        raise ValidationError({"detail": "توکن نامعتبر است یا قبلا منقضی شده است."})