/*
 * Author: Cedric Holzl - Mohamed Khadri
 * Sciper: 257844 - 261203
 */
package ch.epfl.alpano;

import java.util.Locale;
import static java.lang.Math.abs;
import static java.lang.Math.cos;
import static java.lang.Math.sin;
import static java.lang.Math.PI;
import static java.lang.Math.atan2;
import static java.lang.Math.sqrt;
import static java.lang.Math.toDegrees;
import static ch.epfl.alpano.Preconditions.checkArgument;
import static ch.epfl.alpano.Math2.haversin;
import static ch.epfl.alpano.Distance.toMeters;
import static ch.epfl.alpano.Azimuth.fromMath;
import static ch.epfl.alpano.Azimuth.canonicalize;

/**
 * Definition of a geographical point on Earth's surface using spherical
 * coordinates.
 */
public class GeoPoint {

    private final double longitude;
    private final double latitude;

    /**
     * Constructor of a GeoPoint
     * 
     * @param longitude
     *            : longitude position
     * @param latitude
     *            : latitude position
     * @throws IllegalArgumentException
     *             if longitude is not in [−Pi;Pi] or latitude is not in
     *             [−2Pi;2Pi]
     */
    public GeoPoint(double longitude, double latitude) {
        checkArgument(!(abs(longitude) > PI || abs(latitude) * 2.0 > PI));

        this.longitude = longitude;
        this.latitude = latitude;
    }

    /**
     * Returns the longitude value of the GeoPoint
     * 
     * @return longitude
     */
    public double longitude() {
        return this.longitude;
    }

    /**
     * Returns the latitude value of the GeoPoint
     * 
     * @return latitude
     */
    public double latitude() {
        return this.latitude;
    }

    /**
     * Computes the distance between two points
     * 
     * @param that
     *            : a GeoPoint
     * @return distance in meters between two points
     */
    public double distanceTo(GeoPoint that) {
        return toMeters(
                2 * Math.asin(sqrt(haversin(this.latitude - that.latitude)
                        + cos(this.latitude) * cos(that.latitude)
                                * haversin(this.longitude - that.longitude))));
    }

    /**
     * Mathematical angular distance from a geoPoint to another
     * 
     * @param that
     * @return angle expressed in radian in the mathematical convention
     */
    private double mathAzimuthTo(GeoPoint that) {
        return atan2(
                (sin(this.longitude - that.longitude) * cos(that.latitude)),
                (cos(this.latitude) * sin(that.latitude)
                        - sin(this.latitude) * cos(that.latitude)
                                * cos(this.longitude - that.longitude)));
    }

    /**
     * Angular distance from a geoPoint to another in azimuth
     * 
     * @param that
     *            : a GeoPoint
     * @return angle expressed in radian in the azimuth convention
     */
    public double azimuthTo(GeoPoint that) {
        return fromMath(canonicalize(mathAzimuthTo(that)));
    }

    /**
     * Redefines the to String method
     * 
     * @return a string , [lon,lat], lon and lat being the longitude and
     *         latitude values of the GeoPoint
     */
    @Override
    public String toString() {
        return String.format((Locale) null, "(%.4f,%.4f)",
                toDegrees(this.longitude), toDegrees(this.latitude));
    }
}