"""TfL single fare calculations for journeys within Zone 1."""

from datetime import datetime, time

import holidays

CIRCLE_LINE_PEAK = 3.10
CIRCLE_LINE_OFF_PEAK = 3.00

_ENGLAND_HOLIDAYS = holidays.country_holidays("GB", subdiv="ENG")

_AM_PEAK_START = time(6, 30)
_AM_PEAK_END = time(9, 30)
_PM_PEAK_START = time(16, 0)
_PM_PEAK_END = time(19, 0)


def circle_line_fare(depart_dt: datetime) -> float:
    """Return the TfL Circle line single fare for a given departure datetime.

    Peak (£3.10): Monday–Friday (excluding public holidays),
                  06:30–09:30 and 16:00–19:00.
    Off-peak (£3.00): all other times, weekends, and public holidays.
    """
    if depart_dt.date() in _ENGLAND_HOLIDAYS or depart_dt.weekday() >= 5:
        return CIRCLE_LINE_OFF_PEAK
    t = depart_dt.time()
    if _AM_PEAK_START <= t < _AM_PEAK_END or _PM_PEAK_START <= t < _PM_PEAK_END:
        return CIRCLE_LINE_PEAK
    return CIRCLE_LINE_OFF_PEAK