<?php

require_once(dirname(__FILE__).'/utils.class.php');

interface LatLon {

  public function get_lat();

  public function get_lon();

}

interface Collection {

  public static function get_all();

}

abstract class GeoPoint implements LatLon, Collection {

  /**  distance, by Vincenty formula

       see http://stackoverflow.com/a/10054282

   */

  public function distance($other_point) {

    $earthRadius = 6371;

        // convert from degrees to radians

        $latFrom = deg2rad($this->get_lat());

        $lonFrom = deg2rad($this->get_lon());

        $latTo = deg2rad($other_point->get_lat());

        $lonTo = deg2rad($other_point->get_lon());

        $lonDelta = $lonTo - $lonFrom;

        $a = pow(cos($latTo) * sin($lonDelta), 2) +

          pow(cos($latFrom) * sin($latTo) -

      sin($latFrom) * cos($latTo) * cos($lonDelta), 2);

        $b = sin($latFrom) * sin($latTo) +

      cos($latFrom) * cos($latTo) * cos($lonDelta);

        $angle = atan2(sqrt($a), $b);

        return $angle * $earthRadius;

  }

  /** Gets only the points in a circle of $distance km arround $opint

     @param $target a LatLon

   */

  public static function near_points($target, $distance) {

    $near_points = array();

    foreach (static::get_all() as $point) {

      if ($point->distance($target) < $distance) {

        $near_points[] = $point;

      }

    }

    return $near_points;

  }

}

?>