from datetime import datetime

import pytest
from freezegun import freeze_time

from app.utils import (
    get_london_midnight_in_utc,
    get_midnight_for_day_before,
    convert_utc_to_bst,
    convert_bst_to_utc,
    midnight_n_days_ago,
    last_n_days
)


@pytest.mark.parametrize('date, expected_date', [
    (datetime(2016, 1, 15, 0, 30), datetime(2016, 1, 15, 0, 0)),
    (datetime(2016, 6, 15, 0, 0), datetime(2016, 6, 14, 23, 0)),
    (datetime(2016, 9, 15, 11, 59), datetime(2016, 9, 14, 23, 0)),
])
def test_get_london_midnight_in_utc_returns_expected_date(date, expected_date):
    assert get_london_midnight_in_utc(date) == expected_date


@pytest.mark.parametrize('date, expected_date', [
    (datetime(2016, 1, 15, 0, 30), datetime(2016, 1, 14, 0, 0)),
    (datetime(2016, 7, 15, 0, 0), datetime(2016, 7, 13, 23, 0)),
    (datetime(2016, 8, 23, 11, 59), datetime(2016, 8, 21, 23, 0)),
])
def test_get_midnight_for_day_before_returns_expected_date(date, expected_date):
    assert get_midnight_for_day_before(date) == expected_date


@pytest.mark.parametrize('date, expected_date', [
    (datetime(2017, 3, 26, 23, 0), datetime(2017, 3, 27, 0, 0)),    # 2017 BST switchover
    (datetime(2017, 3, 20, 23, 0), datetime(2017, 3, 20, 23, 0)),
    (datetime(2017, 3, 28, 10, 0), datetime(2017, 3, 28, 11, 0)),
    (datetime(2017, 10, 28, 1, 0), datetime(2017, 10, 28, 2, 0)),
    (datetime(2017, 10, 29, 1, 0), datetime(2017, 10, 29, 1, 0)),
    (datetime(2017, 5, 12, 14), datetime(2017, 5, 12, 15, 0))
])
def test_get_utc_in_bst_returns_expected_date(date, expected_date):
    ret_date = convert_utc_to_bst(date)
    assert ret_date == expected_date


def test_convert_bst_to_utc():
    bst = "2017-05-12 13:15"
    bst_datetime = datetime.strptime(bst, "%Y-%m-%d %H:%M")
    utc = convert_bst_to_utc(bst_datetime)
    assert utc == datetime(2017, 5, 12, 12, 15)


@pytest.mark.parametrize('current_time, arg, expected_datetime', [
    # winter
    ('2018-01-10 23:59', 1, datetime(2018, 1, 9, 0, 0)),
    ('2018-01-11 00:00', 1, datetime(2018, 1, 10, 0, 0)),

    # bst switchover at 1am 25th
    ('2018-03-25 10:00', 1, datetime(2018, 3, 24, 0, 0)),
    ('2018-03-26 10:00', 1, datetime(2018, 3, 25, 0, 0)),
    ('2018-03-27 10:00', 1, datetime(2018, 3, 25, 23, 0)),

    # summer
    ('2018-06-05 10:00', 1, datetime(2018, 6, 3, 23, 0)),

    # zero days ago
    ('2018-01-11 00:00', 0, datetime(2018, 1, 11, 0, 0)),
    ('2018-06-05 10:00', 0, datetime(2018, 6, 4, 23, 0)),
])
def test_midnight_n_days_ago(current_time, arg, expected_datetime):
    with freeze_time(current_time):
        assert midnight_n_days_ago(arg) == expected_datetime


def test_last_n_days():
    with freeze_time('2018-03-27 12:00'):
        res = last_n_days(5)

    assert res == [
        datetime(2018, 3, 23, 0, 0),
        datetime(2018, 3, 24, 0, 0),
        datetime(2018, 3, 25, 0, 0),
        datetime(2018, 3, 26, 0, 0),
        datetime(2018, 3, 27, 0, 0)
    ]


@pytest.mark.parametrize('arg', [0, -1])
def test_last_n_days_invalid_arg(arg):
    assert last_n_days(arg) == []