import phonenumbers
from phonenumbers import NumberParseException
from typing import Optional

def normalize_phone(phone: str, default_region: str = "US") -> Optional[str]:
    """
    Normalize a phone number to E.164 format.
    For Telegram provider, accepts plain user IDs (just digits).
    Returns None if the phone number is invalid.
    """
    try:
        # Clean the phone number
        phone = str(phone).strip()
        
        # If it's a short number (< 11 digits), treat as Telegram ID
        # Telegram user IDs are typically 9-10 digits
        if phone.isdigit() and len(phone) <= 10:
            return phone  # Return as-is for Telegram
        
        # For longer numbers, try phone number validation
        # If phone doesn't start with '+', try adding it
        if phone and not phone.startswith('+'):
            phone = '+' + phone
        
        parsed = phonenumbers.parse(phone, default_region)
        if phonenumbers.is_valid_number(parsed):
            return phonenumbers.format_number(parsed, phonenumbers.PhoneNumberFormat.E164)
        return None
    except NumberParseException:
        return None