package tool

import (
	"math"
)

var a = float64(6378137)

var b = 6356752.3142

var asqr = a * a

var bsqr = b * b

var e = math.Sqrt((asqr - bsqr) / asqr)

var eprime = math.Sqrt((asqr - bsqr) / bsqr)

func Xyz2Wgs84(X, Y, Z float64) (lng, lat, height float64) {
	var p = math.Sqrt(X*X + Y*Y)
	var theta = math.Atan((Z * a) / (p * b))
	var sintheta = math.Sin(theta)
	var costheta = math.Cos(theta)
	var num = Z + eprime*eprime*b*sintheta*sintheta*sintheta
	var denom = p - e*e*a*costheta*costheta*costheta
	//Now calculate LLA
	var latitude = math.Atan(num / denom)
	var longitude = math.Atan(Y / X)
	var N = getN(latitude)
	var altitude = (p / math.Cos(latitude)) - N

	if X < 0 && Y < 0 {
		longitude = longitude - math.Pi
	}

	if X < 0 && Y > 0 {
		longitude = longitude + math.Pi
	}
	return radiansToDegrees(longitude), radiansToDegrees(latitude), altitude
}

func getN(latitude float64) float64 {
	var sinlatitude = math.Sin(latitude)
	var denom = math.Sqrt(1 - e*e*sinlatitude*sinlatitude)
	var N = a / denom
	return N
}
func radiansToDegrees(radians float64) float64 {
	return radians * 180 / math.Pi
}

//106.54959740614493 23.47200769358978