// The Airport class holds each airport object
package distanceAndBearing;
public class Airport {
	private String airport;
	private String country;
	private String icao;
	private double lat;
	private double lon;
	public String getAirportName() {	return this.airport;	}
	public void setAirportName(String airport) {	this.airport = airport; }
	public String getCountry() {	return this.country;	}
	public void setCountry(String country) {	this.country = country;	}
	public String getIcao() { return this.icao; }
	public void setIcao(String icao) { this.icao = icao;	}
	public double getLat() {	return this.lat; }
	public void setLat(double lat) {	this.lat = lat;	}
	public double getLon() {	return this.lon; }
	public void setLon(double lon) {	this.lon = lon;	}
	@Override
	public String toString() {return "Airport: " + getAirportName() + ": ICAO: " + getIcao();}
}

// The DistanceAndBearing class does all the work.
package distanceAndBearing;
import java.io.File;
import java.text.DecimalFormat;
import java.util.ArrayList;
import java.util.Collections;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Scanner;
import java.util.stream.Collectors;
public class DistanceAndBearing {
	private final double earthRadius = 6371;
	private File datFile;
	private List<Airport> airports;
	public DistanceAndBearing() { this.airports = new ArrayList<Airport>(); }
	public boolean readFile(String filename) {
		this.datFile = new File(filename);
		try {
			Scanner fileScanner = new Scanner(datFile);
			String line;
			while (fileScanner.hasNextLine()) {
				line = fileScanner.nextLine();
				line = line.replace(", ", "; "); // There are some commas in airport names in the dat
													// file
				line = line.replace(",\",\"", "\",\""); // There are some airport names that
														// end in a comma in the dat file
				String[] parts = line.split(",");
				Airport airport = new Airport();
				airport.setAirportName(parts[1].replace("\"", "")); // Remove the double quotes from the string
				airport.setCountry(parts[3].replace("\"", "")); // Remove the double quotes from the string
				airport.setIcao(parts[5].replace("\"", "")); // Remove the double quotes from the string
				airport.setLat(Double.valueOf(parts[6]));
				airport.setLon(Double.valueOf(parts[7]));
				this.airports.add(airport);
			}
			fileScanner.close();
			return true; // Return true if the read was successful
		} catch (Exception e) {
			e.printStackTrace();
			return false; // Return false if the read was not successful
		}}
	public double[] calculate(double lat1, double lon1, double lat2, double lon2) {
		double[] results = new double[2];
		double dLat = Math.toRadians(lat2 - lat1);
		double dLon = Math.toRadians(lon2 - lon1);
		double rlat1 = Math.toRadians(lat1);
		double rlat2 = Math.toRadians(lat2);
		double a = Math.pow(Math.sin(dLat / 2), 2)
				+ Math.pow(Math.sin(dLon / 2), 2) * Math.cos(rlat1) * Math.cos(rlat2);
		double c = 2 * Math.asin(Math.sqrt(a));
		double distance = earthRadius * c;
		DecimalFormat df = new DecimalFormat("#0.00");
		distance = Double.valueOf(df.format(distance));
		results[0] = distance;
		double X = Math.cos(rlat2) * Math.sin(dLon);
		double Y = Math.cos(rlat1) * Math.sin(rlat2) - Math.sin(rlat1) * Math.cos(rlat2) * Math.cos(dLon);
		double heading = Math.atan2(X, Y);
		heading = Math.toDegrees(heading);
		results[1] = heading;
		return results;
	}
	public Airport searchByName(final String name) {
		Airport airport = new Airport();
		List<Airport> results = this.airports.stream().filter(ap -> ap.getAirportName().contains(name))
				.collect(Collectors.toList());
		airport = results.get(0);
		return airport;
	}
	public List<Airport> findClosestAirports(double lat, double lon) {
		// TODO Auto-generated method stub
		Map<Double, Airport> airportDistances = new HashMap<>();
		Map<Double, Airport> airportHeading = new HashMap<>();
		List<Airport> closestAirports = new ArrayList<Airport>();
		// This loop finds the distance and heading for every airport and saves them
		// into two separate Maps
		for (Airport ap : this.airports) {
			double[] result = calculate(lat, lon, ap.getLat(), ap.getLon());
			airportDistances.put(result[0], ap);
			airportHeading.put(result[1], ap);
		}
		// Get the keyset from the distance map and sort it.
		ArrayList<Double> distances = new ArrayList<>(airportDistances.keySet());
		Collections.sort(distances);
		// Get the first 20 airports by finding the value in the distance map for
		// each distance in the sorted Arraylist. Then get the airport name, and
		// use that to search for the airport in the airports List.
		// Save that into a new List
		for (int i = 0; i < 20; i++) { closestAirports.add(searchByName((airportDistances.get(distances.get(i)).getAirportName())));}
		// Find the distance and heading for each of the top 20 airports.
		Map<String, Double> distanceMap = new HashMap<>();
		for (Double d : airportDistances.keySet()) {	distanceMap.put(airportDistances.get(d).getAirportName(), d);}
		Map<String, Double> headingMap = new HashMap<>();
		for (Double d : airportHeading.keySet()) {
            double d2 = d;
            if(d2<0){d2+=360'}
            headingMap.put(airportHeading.get(d).getAirportName(), d2); }

		// Print the results.
		System.out.printf("%-4s %-40s %-25s %-6s %12s %15s\n", "Num", "Airport", "Country", "ICAO", "Distance", "Bearing");
		System.out.println("-----------------------------------------------------------------------------------------------------------");
		int i = 0;
		for (Airport a : closestAirports) {
			System.out.printf("%-4s %-40s %-25s %-6s %12.1f %15.0f\n", ++i, a.getAirportName(), a.getCountry(), a.getIcao(), distanceMap.get(a.getAirportName())*0.5399568, headingMap.get(a.getAirportName()));
		}
		return closestAirports;
	}
}