import pytest
from datetime import datetime
from cpl.core.time.cron import Cron


def test_next_returns_datetime():
    cron = Cron("* * * * *")
    result = cron.next()
    assert isinstance(result, datetime)


def test_next_is_in_the_future():
    cron = Cron("* * * * *")
    result = cron.next()
    assert result > datetime.now()


def test_next_called_multiple_times_is_monotonic():
    cron = Cron("* * * * *")
    results = [cron.next() for _ in range(5)]
    for i in range(1, len(results)):
        assert results[i] > results[i - 1]


def test_every_minute_interval():
    start = datetime(2024, 1, 1, 12, 0, 0)
    cron = Cron("* * * * *", start_time=start)
    first = cron.next()
    second = cron.next()
    diff = (second - first).total_seconds()
    assert diff == 60


def test_hourly_interval():
    start = datetime(2024, 1, 1, 12, 0, 0)
    cron = Cron("0 * * * *", start_time=start)
    first = cron.next()
    second = cron.next()
    diff = (second - first).total_seconds()
    assert diff == 3600


def test_daily_midnight():
    start = datetime(2024, 1, 1, 0, 0, 0)
    cron = Cron("0 0 * * *", start_time=start)
    first = cron.next()
    assert first.hour == 0
    assert first.minute == 0


def test_custom_start_time():
    start = datetime(2024, 6, 15, 10, 30, 0)
    cron = Cron("*/5 * * * *", start_time=start)
    result = cron.next()
    assert result > start


def test_invalid_cron_expression():
    with pytest.raises(Exception):
        Cron("invalid expression")