celery/celery/utils/timeutils.py

from datetime import datetime, timedelta

from carrot.utils import partition

DAYNAMES = "sun", "mon", "tue", "wed", "thu", "fri", "sat"
WEEKDAYS = dict((name, dow) for name, dow in zip(DAYNAMES, range(7)))

RATE_MODIFIER_MAP = {"s": lambda n: n,
                     "m": lambda n: n / 60.0,
                     "h": lambda n: n / 60.0 / 60.0}

HAVE_TIMEDELTA_TOTAL_SECONDS = hasattr(timedelta, "total_seconds")


def timedelta_seconds(delta):
    """Convert :class:`datetime.timedelta` to seconds.

    Doesn't account for negative values.

    """
    if HAVE_TIMEDELTA_TOTAL_SECONDS:
        # Should return 0 for negative seconds
        return max(delta.total_seconds(), 0)
    if delta.days < 0:
        return 0
    return delta.days * 86400 + delta.seconds + (delta.microseconds / 10e5)


def delta_resolution(dt, delta):
    """Round a datetime to the resolution of a timedelta.

    If the timedelta is in days, the datetime will be rounded
    to the nearest days, if the timedelta is in hours the datetime
    will be rounded to the nearest hour, and so on until seconds
    which will just return the original datetime.

    """
    delta = timedelta_seconds(delta)

    resolutions = ((3, lambda x: x / 86400),
                   (4, lambda x: x / 3600),
                   (5, lambda x: x / 60))

    args = dt.year, dt.month, dt.day, dt.hour, dt.minute, dt.second
    for res, predicate in resolutions:
        if predicate(delta) >= 1.0:
            return datetime(*args[:res])
    return dt


def remaining(start, ends_in, now=None, relative=True):
    """Calculate the remaining time for a start date and a timedelta.

    E.g. "how many seconds left for 30 seconds after ``start``?"

    :param start: Start :class:`datetime.datetime`.
    :param ends_in: The end delta as a :class:`datetime.timedelta`.

    :keyword relative: If set to ``False``, the end time will be calculated
        using :func:`delta_resolution` (i.e. rounded to the resolution
          of ``ends_in``).
    :keyword now: The current time, defaults to :func:`datetime.now`.

    """
    now = now or datetime.now()

    end_date = start + ends_in
    if not relative:
        end_date = delta_resolution(end_date, ends_in)
    return end_date - now


def rate(rate):
    """Parses rate strings, such as ``"100/m"`` or ``"2/h"``
    and converts them to seconds."""
    if rate:
        if isinstance(rate, basestring):
            ops, _, modifier = partition(rate, "/")
            return RATE_MODIFIER_MAP[modifier or "s"](int(ops)) or 0
        return rate or 0
    return 0


def weekday(name):
    """Return the position of a weekday (0 - 7, where 0 is Sunday).

    Example::

        >>> weekday("sunday"), weekday("sun"), weekday("mon")
        (0, 0, 1)

    """
    abbreviation = name[0:3].lower()
    try:
        return WEEKDAYS[abbreviation]
    except KeyError:
        # Show original day name in exception, instead of abbr.
        raise KeyError(name)