import datetime, math, time

from django.utils.tzinfo import LocalTimezone

from django.utils.translation import ngettext

def timesince(d, now=None):

    """

    Takes two datetime objects and returns the time between then and now

    as a nicely formatted string, e.g "10 minutes"

    Adapted from http://blog.natbat.co.uk/archive/2003/Jun/14/time_since

    """

    chunks = (

      (60 * 60 * 24 * 365, lambda n: ngettext('year', 'years', n)),

      (60 * 60 * 24 * 30, lambda n: ngettext('month', 'months', n)),

      (60 * 60 * 24 * 7, lambda n : ngettext('week', 'weeks', n)),

      (60 * 60 * 24, lambda n : ngettext('day', 'days', n)),

      (60 * 60, lambda n: ngettext('hour', 'hours', n)),

      (60, lambda n: ngettext('minute', 'minutes', n))

    )

    # Convert datetime.date to datetime.datetime for comparison

    if d.__class__ is not datetime.datetime:

        d = datetime.datetime(d.year, d.month, d.day)

    if now:

        t = now.timetuple()

    else:

        t = time.localtime()

    if d.tzinfo:

        tz = LocalTimezone(d)

    else:

        tz = None

    now = datetime.datetime(t[0], t[1], t[2], t[3], t[4], t[5], tzinfo=tz)

    # ignore microsecond part of 'd' since we removed it from 'now'

    delta = now - (d - datetime.timedelta(0, 0, d.microsecond))

    since = delta.days * 24 * 60 * 60 + delta.seconds

    for i, (seconds, name) in enumerate(chunks):

        count = since / seconds

        if count != 0:

            break

    if count < 0:

        return '%d milliseconds' % math.floor((now - d).microseconds / 1000)

    s = '%d %s' % (count, name(count))

    if i + 1 < len(chunks):

        # Now get the second item

        seconds2, name2 = chunks[i + 1]

        count2 = (since - (seconds * count)) / seconds2

        if count2 != 0:

            s += ', %d %s' % (count2, name2(count2))

    return s

def timeuntil(d, now=None):

    """

    Like timesince, but returns a string measuring the time until

    the given time.

    """

    if now == None:

        now = datetime.datetime.now()

    return timesince(now, d)