"""Timezone utils."""

from datetime import datetime

import pytz

from src.constants import common_consts
from src.constants import timezones


def convert_to_utc_datetime(local_date, timezone_name=timezones.US_EASTERN):
    """Convert local datetime without timezone to UTC.

    Args:
        local_date (datetime): local time with empty timezone
        timezone_name (str): local timezone name
    Returns:
        datetime: UTC datetime with empty timezone

    """
    tz = pytz.timezone(timezone_name)
    local_date = tz.localize(local_date)
    return local_date.astimezone(pytz.utc).replace(tzinfo=None)


def convert_to_utc_str(local_date, timezone_name=timezones.US_EASTERN):
    """Convert local datetime without timezone to UTC.

    Args:
        local_date (str or datetime): local time with empty timezone
        timezone_name (str): local timezone name

    Returns:
        str or None: UTC datetime with empty timezone as str
        or None if local_date is None.

    Raises:
        ValueError: unknown input date format.

    """
    if local_date is None:
        return None
    if isinstance(local_date, str):
        # Convert to datetime only if it is a string.
        for datetime_format in common_consts.INPUT_DATETIME_FORMATS:
            try:
                local_date = datetime.strptime(local_date, datetime_format)
                break
            except ValueError:
                pass
        else:
            raise ValueError(f'local_date "{local_date}" format is not known.')
    utc_date = convert_to_utc_datetime(local_date, timezone_name)
    return utc_date.strftime(common_consts.OUTPUT_DATETIME_FORMAT)