/**

* 获取两个经纬度坐标正北方向夹角

* @param {Array} o_latlngs 原点经纬度坐标 [经度, 纬度]

* @param {Array} latlngs 经纬度坐标

* @return {Number} 返回角度

*/

function getTwoPointAngle(o_latlngs, latlngs) {

let A = new MyLatLng(o_latlngs[0], o_latlngs[1]);

let B = new MyLatLng(latlngs[0], latlngs[1]);

// console.log(getAngle(B, A));

return getAngle(B, A);

}

/**

* 求B点经纬度

* @param A 已知点的经纬度，

* @param distance AB两地的距离 单位km

* @param angle AB连线与正北方向的夹角(0~360)

* @return B点的经纬度

*/

function getMyLatLng(A, distance, angle) {

let dx = distance * 1000 * Math.sin(Math.toRadians(angle));

let dy = distance * 1000 * Math.cos(Math.toRadians(angle));

let bjd = (dx / A.Ed + A.m_RadLo) * 180.0 / Math.PI;

let bwd = (dy / A.Ec + A.m_RadLa) * 180.0 / Math.PI;

return new MyLatLng(bjd, bwd);

}

/**

* 获取AB连线与正北方向的角度

* @param A A点的经纬度

* @param B B点的经纬度

* @return AB连线与正北方向的角度(0~360)

*/

function getAngle(A, B) {

let dx = (B.m_RadLo - A.m_RadLo) * A.Ed;

let dy = (B.m_RadLa - A.m_RadLa) * A.Ec;

let angle = 0.0;

angle = Math.atan(Math.abs(dx / dy)) * 180.0 / Math.PI;

let dLo = B.m_Longitude - A.m_Longitude;

let dLa = B.m_Latitude - A.m_Latitude;

if (dLo > 0 && dLa <= 0) {

angle = (90.0 - angle) + 90;

} else if (dLo <= 0 && dLa < 0) {

angle = angle + 180.0;

} else if (dLo < 0 && dLa >= 0) {

angle = (90.0 - angle) + 270;

}

return angle;

}

class MyLatLng {

constructor(lng, lat) {

const Rc = 6378137; // 赤道半径

const Rj = 6356725; // 极半径

// 经度转为度分秒

this.m_LoDeg = lng;

this.m_LoMin = ((lng - this.m_LoDeg) * 60);

this.m_LoSec = (lng - this.m_LoDeg - this.m_LoMin / 60.0) * 3600;

// 纬度转为度分秒

this.m_LaDeg = lat;

this.m_LaMin = ((lat - this.m_LaDeg) * 60);

this.m_LaSec = (lat - this.m_LaDeg - this.m_LaMin / 60.0) * 3600;

this.m_Longitude = lng;

this.m_Latitude = lat;

this.m_RadLo = lng * Math.PI / 180.0; // 经度弧度

this.m_RadLa = lat * Math.PI / 180.0; // 纬度弧度

this.Ec = Rj + (Rc - Rj) * (90.0 - this.m_Latitude) / 90.0;

this.Ed = this.Ec * Math.cos(this.m_RadLa);

}

}

exports = module.exports = {

getTwoPointAngle: getTwoPointAngle

};