from __future__ import unicode_literals

import calendar
import datetime

from django.utils.html import avoid_wrapping
from django.utils.timezone import is_aware, utc
from django.utils.translation import ugettext, ungettext_lazy

TIMESINCE_CHUNKS = (
    (60 * 60 * 24 * 365, ungettext_lazy('%d year', '%d years')),
    (60 * 60 * 24 * 30, ungettext_lazy('%d month', '%d months')),
    (60 * 60 * 24 * 7, ungettext_lazy('%d week', '%d weeks')),
    (60 * 60 * 24, ungettext_lazy('%d day', '%d days')),
    (60 * 60, ungettext_lazy('%d hour', '%d hours')),
    (60, ungettext_lazy('%d minute', '%d minutes'))
)


def timesince(d, now=None, reversed=False):
    """
    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://web.archive.org/web/20060617175230/http://blog.natbat.co.uk/archive/2003/Jun/14/time_since
    """
    # Convert datetime.date to datetime.datetime for comparison.
    if not isinstance(d, datetime.datetime):
        d = datetime.datetime(d.year, d.month, d.day)
    if now and not isinstance(now, datetime.datetime):
        now = datetime.datetime(now.year, now.month, now.day)

    if not now:
        now = datetime.datetime.now(utc if is_aware(d) else None)

    if reversed:
        d, now = now, d
    delta = now - d

    # Deal with leapyears by subtracing the number of leapdays
    leapdays = calendar.leapdays(d.year, now.year)
    if leapdays != 0:
        if calendar.isleap(d.year):
            leapdays -= 1
        elif calendar.isleap(now.year):
            leapdays += 1
    delta -= datetime.timedelta(leapdays)

    # ignore microseconds
    since = delta.days * 24 * 60 * 60 + delta.seconds
    if since <= 0:
        # d is in the future compared to now, stop processing.
        return avoid_wrapping(ugettext('0 minutes'))
    for i, (seconds, name) in enumerate(TIMESINCE_CHUNKS):
        count = since // seconds
        if count != 0:
            break
    result = avoid_wrapping(name % count)
    if i + 1 < len(TIMESINCE_CHUNKS):
        # Now get the second item
        seconds2, name2 = TIMESINCE_CHUNKS[i + 1]
        count2 = (since - (seconds * count)) // seconds2
        if count2 != 0:
            result += ugettext(', ') + avoid_wrapping(name2 % count2)
    return result


def timeuntil(d, now=None):
    """
    Like timesince, but returns a string measuring the time until
    the given time.
    """
    return timesince(d, now, reversed=True)
