<?php


namespace common\helpers;
class LocationHelper
{
    public $_geo_conf;
    public function __construct()
    {
        $this->_geo_conf = array(
            'pi'           => pi(),
            'EARTH_RADIUS' => 6378.137,
        );
    }

    /**
     * 求两个地理位置之间的距离
     *
     * @param $longitude_a
     * @param $latitude_a
     * @param $longitude_b
     * @param $latitude_b
     * @return bool|float|int
     */
    public function getDistanceByGeo($latitude_a, $longitude_a, $latitude_b, $longitude_b)
    {
        if (!$latitude_a || !$longitude_a || !$latitude_b || !$longitude_b){
            return false;
        }

        $latitude_a_radian = $this->angleToRadian($latitude_a);
        $latitude_b_radian = $this->angleToRadian($latitude_b);

        $longitude_a_radian = $this->angleToRadian($longitude_a);
        $longitude_b_radian =  $this->angleToRadian($longitude_b);

        $latitude_radian_diff = $latitude_a_radian - $latitude_b_radian;
        $longitude_radian_diff = $longitude_a_radian - $longitude_b_radian;

        return 2 * asin(sqrt(pow(sin($latitude_radian_diff / 2), 2) + cos($latitude_a_radian) * cos($latitude_b_radian) * pow(sin($longitude_radian_diff / 2), 2))) * $this->_geo_conf['EARTH_RADIUS'];
        
    }


    /**
     * 角度转弧度
     * @param $angle
     * @return float
     */
    private function angleToRadian($angle)
    {
        return $angle * $this->_geo_conf['pi'] / 180.0;
    }

    /**
     * 格式化距离
     * @param $distance
     * @return string
     */
    public static function formatDistance($distance)
    {
        $distance = bcmul($distance, 1000, 1);
        if ($distance < 1000) return "{$distance}m";
        return bcmul($distance, 0.001, 2) . "km";
    }
}