Added arn to the main repository

arn/Location.go

@@ -0,0 +1,53 @@
+package arn
+
+import "math"
+
+// EarthRadius is the radius of the earth in kilometers.
+const EarthRadius = 6371
+
+// Location ...
+type Location struct {
+	CountryName string  `json:"countryName"`
+	CountryCode string  `json:"countryCode"`
+	Latitude    float64 `json:"latitude" editable:"true"`
+	Longitude   float64 `json:"longitude" editable:"true"`
+	CityName    string  `json:"cityName"`
+	RegionName  string  `json:"regionName"`
+	TimeZone    string  `json:"timeZone"`
+	ZipCode     string  `json:"zipCode"`
+}
+
+// IPInfoDBLocation ...
+type IPInfoDBLocation struct {
+	CountryName string `json:"countryName"`
+	CountryCode string `json:"countryCode"`
+	Latitude    string `json:"latitude"`
+	Longitude   string `json:"longitude"`
+	CityName    string `json:"cityName"`
+	RegionName  string `json:"regionName"`
+	TimeZone    string `json:"timeZone"`
+	ZipCode     string `json:"zipCode"`
+}
+
+// IsValid returns true if latitude and longitude are available.
+func (p *Location) IsValid() bool {
+	return p.Latitude != 0 && p.Longitude != 0
+}
+
+// Distance calculates the distance in kilometers to the second location.
+// Original implementation: https://www.movable-type.co.uk/scripts/latlong.html
+func (p *Location) Distance(p2 *Location) float64 {
+	dLat := (p2.Latitude - p.Latitude) * (math.Pi / 180.0)
+	dLon := (p2.Longitude - p.Longitude) * (math.Pi / 180.0)
+
+	lat1 := p.Latitude * (math.Pi / 180.0)
+	lat2 := p2.Latitude * (math.Pi / 180.0)
+
+	a1 := math.Sin(dLat/2) * math.Sin(dLat/2)
+	a2 := math.Sin(dLon/2) * math.Sin(dLon/2) * math.Cos(lat1) * math.Cos(lat2)
+
+	a := a1 + a2
+	c := 2 * math.Atan2(math.Sqrt(a), math.Sqrt(1-a))
+
+	return EarthRadius * c
+}