/*
 * Copyright (C) 2008 Google Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package ch.bfh.fbi.mobiComp.PeopleTag.gui;

//import com.google.android.maps.GeoPoint;

/**
 * Library for some use useful latitude/longitude math
 */
public class GeoUtils {
    private static int EARTH_RADIUS_KM = 6371;

    public static int MILLION = 1000000;

    /**
     * Computes the distance in kilometers between two points on Earth.
     * 
     * @param lat1 Latitude of the first point
     * @param lon1 Longitude of the first point
     * @param lat2 Latitude of the second point
     * @param lon2 Longitude of the second point
     * @return Distance between the two points in kilometers.
     */
    public static double distanceKm(double lat1, double lon1, double lat2, double lon2) {
        double lat1Rad = Math.toRadians(lat1);
        double lat2Rad = Math.toRadians(lat2);
        double deltaLonRad = Math.toRadians(lon2 - lon1);
        
        return Math.acos(Math.sin(lat1Rad) * Math.sin(lat2Rad) + Math.cos(lat1Rad) * Math.cos(lat2Rad)
                * Math.cos(deltaLonRad))
                * EARTH_RADIUS_KM;
    }
    
    /**
     * Computes the distance in kilometers between two points on Earth.
     * 
     * @param p1 First point
     * @param p2 Second point
     * @return Distance between the two points in kilometers.
     /
    public static double distanceKm(GeoPoint p1, GeoPoint p2) {
        double lat1 = p1.getLatitudeE6() / (double)MILLION;
        double lon1 = p1.getLongitudeE6() / (double)MILLION;
        double lat2 = p2.getLatitudeE6() / (double)MILLION;
        double lon2 = p2.getLongitudeE6() / (double)MILLION;

        return distanceKm(lat1, lon1, lat2, lon2);
    }
    
    /**
     * Computes the bearing in degrees between two points on Earth.
     * 
     * @param p1 First point
     * @param p2 Second point
     * @return Bearing between the two points in degrees. A value of 0 means due
     *         north.
     /
    public static double bearing(GeoPoint p1, GeoPoint p2) {
        double lat1 = p1.getLatitudeE6() / (double) MILLION;
        double lon1 = p1.getLongitudeE6() / (double) MILLION;
        double lat2 = p2.getLatitudeE6() / (double) MILLION;
        double lon2 = p2.getLongitudeE6() / (double) MILLION;

        return bearing(lat1, lon1, lat2, lon2);
    }
    
    /**
     * Computes the bearing in degrees between two points on Earth.
     * 
     * @param lat1 Latitude of the first point
     * @param lon1 Longitude of the first point
     * @param lat2 Latitude of the second point
     * @param lon2 Longitude of the second point
     * @return Bearing between the two points in degrees. A value of 0 means due
     *         north.
     */
    public static double bearing(double lat1, double lon1, double lat2, double lon2) {
        double lat1Rad = Math.toRadians(lat1);
        double lat2Rad = Math.toRadians(lat2);
        double deltaLonRad = Math.toRadians(lon2 - lon1);

        double y = Math.sin(deltaLonRad) * Math.cos(lat2Rad);
        double x = Math.cos(lat1Rad) * Math.sin(lat2Rad) - Math.sin(lat1Rad) * Math.cos(lat2Rad)
                * Math.cos(deltaLonRad);
        return radToBearing(Math.atan2(y, x));
    }
    
    /**
     * Converts an angle in radians to degrees
     */
    public static double radToBearing(double rad) {
        return (Math.toDegrees(rad) + 360) % 360;
    }
}