SpeedCalculator

package dailyprogrammer.medium.averagespeedcameras;

import java.io.File;
import java.time.Duration;
import java.time.LocalTime;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.stream.IntStream;

public class SpeedCalculator {

    private LogParser parser;

    private List<CameraLog> cameras;

    SpeedCalculator() {
        this.parser = new LogParser();
    }

    public List<Pair<String, Double>> getSpeedingCars(File logFile) throws Exception {
        parser.parseLog(logFile);
        cameras = parser.getCameras();
        List<Pair<String, Double>> ret = Collections.synchronizedList(new ArrayList<>());
        parser.getCars().stream().parallel()
            .forEach(car -> checkSpeed(car, parser.getDistMeasure(), ret));
        return ret;
    }

    private void checkSpeed(String car, LogParser.DistMeasure distMeasure, List<Pair<String, Double>> lst) {
        IntStream.range(0, cameras.size() - 1).forEach(i -> {
            CameraLog cam1  = cameras.get(i);
            CameraLog cam2  = cameras.get(i + 1);
            LocalTime time1 = cam1.getCarPassTime(car);
            LocalTime time2 = cam2.getCarPassTime(car);
            double div      = distMeasure == LogParser.DistMeasure.KM ? 1000.0 : 1609.0;
            double camDist  = (cam2.getDist() - cam1.getDist()) / div;
            double duration = Duration.between(time1, time2).toNanos() / 1e9 / 60.0 / 60.0;
            double speed    = camDist / duration;
            if (speed > parser.getSpeedLimit()) lst.add(new Pair<>(car, speed - parser.getSpeedLimit()));
        });
    }

    public String getDistString() {
        return parser.getDistMeasure() == LogParser.DistMeasure.KM ? "km/h" : "mph";
    }

}