package zombie.vehicles;

import java.util.HashSet;
import java.util.Set;
import zombie.characters.IsoGameCharacter;

/**
 * Resolves the effective driver for constraint auth in chained towing.
 * For middle vehicles in a chain, scan through links so long trains still resolve authority.
 */
public final class LandtrainConstraintAuthHelper {
    private LandtrainConstraintAuthHelper() {
    }

    public static IsoGameCharacter resolveConstraintDriver(BaseVehicle vehicle) {
        if (vehicle == null) {
            return null;
        }

        IsoGameCharacter driver = findDriverAlongChain(vehicle, true);
        if (driver != null) return driver;
        return findDriverAlongChain(vehicle, false);
    }

    private static IsoGameCharacter findDriverAlongChain(BaseVehicle start, boolean towardFront) {
        BaseVehicle cursor = start;
        Set<Integer> visited = new HashSet<>();

        while (cursor != null) {
            int id = cursor.getId();
            if (!visited.add(id)) {
                // Safety: malformed link graph; stop scanning.
                return null;
            }

            IsoGameCharacter driver = cursor.getDriver();
            if (driver != null) {
                return driver;
            }

            cursor = towardFront ? cursor.getVehicleTowedBy() : cursor.getVehicleTowing();
        }

        return null;
    }

    public static boolean isEnterBlockedLandtrain(
            BaseVehicle vehicle, IsoGameCharacter chr, int seat) {
        if (isVehicleBeingTowedInLandtrain(vehicle)) {
            return true;
        }
        return vehicle != null && vehicle.isExitBlocked(chr, seat);
    }

    public static boolean isEnterBlocked2Landtrain(BaseVehicle vehicle, int seat) {
        if (isVehicleBeingTowedInLandtrain(vehicle)) {
            return true;
        }
        return vehicle != null && vehicle.isExitBlocked2(seat);
    }

    private static boolean isVehicleBeingTowedInLandtrain(BaseVehicle vehicle) {
        return vehicle != null && vehicle.getVehicleTowedBy() != null;
    }
}