"""
Timezone utilities for CEST/CET conversion
"""
from datetime import datetime, timezone
import pytz

def get_cest_timezone():
    """Get CEST/CET timezone (Europe/Berlin)"""
    return pytz.timezone('Europe/Berlin')

def get_server_timezone():
    """Get server's local timezone (IST)"""
    return pytz.timezone('Asia/Kolkata')

def utc_to_cest(utc_datetime):
    """
    Convert UTC datetime to CEST/CET timezone
    
    Args:
        utc_datetime: UTC datetime object
        
    Returns:
        datetime object in CEST/CET timezone
    """
    if utc_datetime is None:
        return None
    
    # Ensure the datetime is timezone-aware
    if utc_datetime.tzinfo is None:
        utc_datetime = utc_datetime.replace(tzinfo=timezone.utc)
    
    cest_tz = get_cest_timezone()
    return utc_datetime.astimezone(cest_tz)

def local_to_cest(local_datetime):
    """
    Convert local server time (IST) to CEST/CET timezone
    
    Args:
        local_datetime: Local datetime object (from server)
        
    Returns:
        datetime object in CEST/CET timezone
    """
    if local_datetime is None:
        return None
    
    # First, make the local datetime timezone-aware
    ist_tz = get_server_timezone()
    if local_datetime.tzinfo is None:
        local_datetime = ist_tz.localize(local_datetime)
    
    # Convert to CEST/CET
    cest_tz = get_cest_timezone()
    return local_datetime.astimezone(cest_tz)

def format_cest_datetime(utc_datetime, format_str="%Y-%m-%d %H:%M:%S"):
    """
    Format UTC datetime to CEST/CET timezone string
    
    Args:
        utc_datetime: UTC datetime object
        format_str: Format string for datetime
        
    Returns:
        Formatted string in CEST/CET timezone
    """
    if utc_datetime is None:
        return None
    
    # Convert local server time to CEST/CET
    cest_datetime = local_to_cest(utc_datetime)
    return cest_datetime.strftime(format_str)

def now_cest():
    """
    Get current time in CEST/CET timezone
    
    Returns:
        datetime object in CEST/CET timezone
    """
    cest_tz = get_cest_timezone()
    return datetime.now(cest_tz)