Add distance calculations to Location

1 files changed, 59 insertions, 0 deletions

diff --git a/mullvad-types/src/location.rs b/mullvad-types/src/location.rs
index 1c59c0d416..514ce35809 100644
--- a/mullvad-types/src/location.rs
+++ b/mullvad-types/src/location.rs
@@ -15,6 +15,42 @@ pub struct Location {
     pub longitude: f64,
 }
 
+const RAIDUS_OF_EARTH: f64 = 6372.8;
+
+impl Location {
+    pub fn distance_from(&self, other: &Location) -> f64 {
+        haversine_dist_deg(
+            self.latitude,
+            self.longitude,
+            other.latitude,
+            other.longitude,
+        )
+    }
+}
+
+/// Takes input as latitude and longitude degrees.
+fn haversine_dist_deg(lat: f64, lon: f64, other_lat: f64, other_lon: f64) -> f64 {
+    haversine_dist_rad(
+        lat.to_radians(),
+        lon.to_radians(),
+        other_lat.to_radians(),
+        other_lon.to_radians(),
+    )
+}
+/// Implemented as per https://en.wikipedia.org/wiki/Haversine_formula and https://rosettacode.org/wiki/Haversine_formula#Rust
+/// Takes input as radians, outputs kilometers.
+fn haversine_dist_rad(lat: f64, lon: f64, other_lat: f64, other_lon: f64) -> f64 {
+    let d_lat = lat - other_lat;
+    let d_lon = lon - other_lon;
+    // Computing the haversine between two points
+    let haversine =
+        (d_lat / 2.0).sin().powi(2) + (d_lon / 2.0).sin().powi(2) * lat.cos() * other_lat.cos();
+
+    // using the haversine to compute the distance between two points
+    haversine.sqrt().asin() * 2.0 * RAIDUS_OF_EARTH
+}
+
+
 /// The response from the am.i.mullvad.net location service.
 #[derive(Debug, Deserialize)]
 pub struct AmIMullvad {
@@ -57,3 +93,26 @@ impl From<AmIMullvad> for GeoIpLocation {
         }
     }
 }
+
+#[cfg(test)]
+mod tests {
+    #[test]
+    fn test_haversine_dist_deg() {
+        use super::haversine_dist_deg;
+        assert_eq!(
+            haversine_dist_deg(36.12, -86.67, 33.94, -118.4),
+            2887.2599506071111
+        );
+        assert_eq!(
+            haversine_dist_deg(90.0, 5.0, 90.0, 79.0),
+            0.0000000000004696822692507987
+        );
+        assert_eq!(haversine_dist_deg(0.0, 0.0, 0.0, 0.0), 0.0);
+        assert_eq!(haversine_dist_deg(49.0, 12.0, 49.0, 12.0), 0.0);
+        assert_eq!(haversine_dist_deg(6.0, 27.0, 7.0, 27.0), 111.22634257109462);
+        assert_eq!(
+            haversine_dist_deg(0.0, 179.5, 0.0, -179.5),
+            111.22634257109495
+        );
+    }
+}