import datetime

import time

from django.utils.tzinfo import LocalTimezone

from django.utils.translation import ungettext, ugettext

def timesince(d, now=None):

    """

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

    as a nicely formatted string, e.g. "10 minutes".  If d occurs after now,

    then "0 minutes" is returned.

    Units used are years, months, weeks, days, hours, and minutes.

    Seconds and microseconds are ignored.  Up to two adjacent units will be

    displayed.  For example, "2 weeks, 3 days" and "1 year, 3 months" are

    possible outputs, but "2 weeks, 3 hours" and "1 year, 5 days" are not.

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

    """

    chunks = (

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

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

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

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

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

      (60, lambda n: ungettext('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

    if since <= 0:

        # d is in the future compared to now, stop processing.

        return u'0 ' + ugettext('minutes')

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

        count = since // seconds

        if count != 0:

            break

    s = ugettext('%(number)d %(type)s') % {'number': count, 'type': 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 += ugettext(', %(number)d %(type)s') % {'number': count2, 'type': 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)