int_to_timestamp.py

from datetime import date
from datetime import datetime as dt
from typing import Union, cast

from dateutil.tz import tzlocal, tzutc


DATETIME_FORMAT = '%Y-%m-%dT%H:%M:%SZ'

def int_to_timestamp(
    value: int,
    mode='MICROSECONDS',
    format=DATETIME_FORMAT,
    tz=tzutc(),
    *,
    as_datetime=False
) -> Union[str, dt, date]:
    """Convert integer milliseconds to datetime (string) (default UTC).

    Raises KeyError if mode doesn't exist.
    """
    denomenator = {
        'DAYS': 1 / 86400,
        'SECONDS': 1,
        'MILLISECONDS': 1000,
        'MICROSECONDS': 1000_000,
    }[mode]
    ts_value = dt.fromtimestamp(value / denomenator, tz=tz)
    if not as_datetime:
        return ts_value.strftime(format)
    elif mode == 'DAYS':
        return ts_value.date()
    else:
        return ts_value


def timestamp_to_int(
    value: Union[str, dt, date],
    mode='MICROSECONDS',
    format=DATETIME_FORMAT,
    tz=tzutc()
) -> int:
    """Convert datetime (string) to integer milliseconds (default UTC).

    Raises KeyError if mode doesn't exist.
    """
    if type(value) is date:
        value = dt.combine(value, dt.min.time())
    epoch = dt(1970, 1, 1, 0, 0, 0, tzinfo=tzutc())
    ts = (
        cast(dt, (
            dt.strptime(value, format)
            if isinstance(value, str)
            else value
        ))
        .astimezone(tzlocal())
        .replace(tzinfo=tz)
    )
    diff = (ts - epoch).total_seconds()
    res = {
        'DAYS': diff / 86400,
        'SECONDS': diff,
        'MILLISECONDS': diff * 1000,
        'MICROSECONDS': diff * 1000_000,
    }[mode]
    return int(res)