"""Utilities to support splitting fuel and car maintainance costs"""

import typing as T

PassengerResult = dict[str, int]
Results = dict[str, PassengerResult]
TankenFailure = T.Tuple[None, str]
TankenSuccess = T.Tuple[Results, None]
TankenResult = T.Union[TankenSuccess, TankenFailure]


# cost should be given in cents
def tanken(_drives: list[str], cost: int, service_charge=0) -> TankenResult:
    """calculate costs per passange for one tank load"""
    passengers = {}
    distance = 0.
    drives = [d.split(' ') for d in _drives]

    for drive in drives:
        try:
            drive_distance = int(drive[0])
        except (IndexError, ValueError):
            return None, "Lines have to start with the driven distance!"

        # calculate overall distance
        distance += drive_distance

        # collect distances per passenger
        for passenger in drive[1:]:
            if passenger not in passengers:
                passengers[passenger] = {
                    "distance": drive_distance,
                    "cost": 0,
                    "service_charge": 0
                }
            else:
                passengers[passenger]["distance"] += drive_distance

    # calculate cost per kilometer
    if distance <= 0:
        return None, "Driven distance must be greater than 0!"

    c_km = cost / distance

    for drive in drives:
        drive_distance = int(drive[0])
        # calculate cost per drive split among passengers
        c_d = int(c_km * drive_distance / (len(drive) - 1))
        for passenger in drive[1:]:
            passengers[passenger]["cost"] += c_d

        # calculate service charge per drive split among passengers
        sc_d = int(service_charge * drive_distance / (len(drive) - 1))
        for passenger in drive[1:]:
            passengers[passenger]["service_charge"] += sc_d

    return passengers, None