public List<Track> getHighestPriorityThreats(List<Track> tracks, int k) {
    // Guard: null/empty/k≤0
    if (tracks == null || tracks.isEmpty() || k <= 0)
        return Collections.emptyList();

    // Min-heap: smallest TTI = highest threat priority
    PriorityQueue<Track> pq = new PriorityQueue<>(
        (a, b) -> Double.compare(a.getTimeToImpact(), b.getTimeToImpact())
    );

    for (Track t : tracks) {
        if (t.isHostile() && !t.isNeutralized())
            pq.offer(t);
    }

    List<Track> result = new ArrayList<>();
    while (!pq.isEmpty() && result.size() < k)
        result.add(pq.poll());
    return result;
}

// Interface — open for new sensor types without modifying ingest()
public interface SensorParser {
    Track parseRecord(byte[] rawPayload);
}

public class SensorIngestionService {
    private final Map<SensorType, SensorParser> parsers = new HashMap<>();
    private final Map<String, Track> activeTracks = new ConcurrentHashMap<>();

    public void registerParser(SensorType type, SensorParser parser) {
        parsers.put(type, parser);   // Open/Closed: add types without editing ingest()
    }

    public void ingest(SensorType type, byte[] rawData) {
        SensorParser parser = parsers.get(type);
        if (parser == null)
            throw new IllegalArgumentException("No parser for " + type);
        Track track = parser.parseRecord(rawData);
        if (track != null && track.isValid())
            activeTracks.put(track.getTrackId(), track);
    }
}

public void ingest(Track track) {
    // 1. Null guard
    if (track == null) return;

    // 2. ID guard
    if (track.getTrackId() == null || track.getTrackId().isEmpty()) return;

    // 3. Coordinate bounds
    double lat = track.getLat(), lon = track.getLon();
    if (lat < -90.0 || lat > 90.0 || lon < -180.0 || lon > 180.0) return;

    // 4 + 5. Upsert (overwrite existing or insert new)
    activeTracks.put(track.getTrackId(), track);
}