from icalendar.prop import vDatetime
import pytest
from datetime import datetime


def test_to_ical():
    assert vDatetime(datetime(2001, 1, 1, 12, 30, 0)).to_ical() == b'20010101T123000'

def test_from_ical():
    assert vDatetime.from_ical('20000101T120000') == datetime(2000, 1, 1, 12, 0)
    assert vDatetime.from_ical('20010101T000000') == datetime(2001, 1, 1,  0, 0)

def test_to_ical_utc(tzp):
    dutc = tzp.localize_utc(datetime(2001, 1, 1, 12, 30, 0))
    assert vDatetime(dutc).to_ical() == b'20010101T123000Z'

def test_to_ical_utc_1899(tzp):
    dutc = tzp.localize_utc(datetime(1899, 1, 1, 12, 30, 0))
    assert vDatetime(dutc).to_ical() == b'18990101T123000Z'


def test_bad_ical():
    with pytest.raises(ValueError):
        vDatetime.from_ical('20010101T000000A')


def test_roundtrip():
    utc = vDatetime.from_ical('20010101T000000Z')
    assert vDatetime(utc).to_ical() == b'20010101T000000Z'


def test_transition(tzp):
    # 1 minute before transition to DST
    dat = vDatetime.from_ical('20120311T015959', 'America/Denver')
    assert dat.strftime('%Y%m%d%H%M%S %z') =='20120311015959 -0700'

    # After transition to DST
    dat = vDatetime.from_ical('20120311T030000', 'America/Denver')
    assert dat.strftime('%Y%m%d%H%M%S %z') == '20120311030000 -0600'

    dat = vDatetime.from_ical('20101010T000000', 'Europe/Vienna')
    assert vDatetime(dat).to_ical() == b'20101010T000000'