From 4c77c8435dfaaaab8233c006d0ba29518517bcda Mon Sep 17 00:00:00 2001
From: Christian Weimann <mail@christian-weimann.de>
Date: Sat, 14 Oct 2023 05:27:23 +0200
Subject: [PATCH] First commit of distanceFrom function

---
 utils/lib.js | 30 +++++++++++++++++++++++++++++-
 1 file changed, 29 insertions(+), 1 deletion(-)

diff --git a/utils/lib.js b/utils/lib.js
index d1cd070..1986aff 100644
--- a/utils/lib.js
+++ b/utils/lib.js
@@ -96,8 +96,36 @@ function convertValue(value) {
     }
 }
 
+function distanceFrom(locationA, locationB) {
+    console.debug(`Calculate distance between ${locationA} and ${locationB}`);
+
+    let lat1 = (locationA.split(',')[0]) * (Math.PI / 180);
+    let lon1 = (locationA.split(',')[1]) * (Math.PI / 180);
+    let lat2 = (locationB.split(',')[0]) * (Math.PI / 180);
+    let lon2 = (locationB.split(',')[1]) * (Math.PI / 180);
+    
+	if ((lat1 == lat2) && (lon1 == lon2)) {
+		return 0;
+	}
+
+    // Haversine formula
+    let dlon = lon2 - lon1;
+    let dlat = lat2 - lat1;
+    let a = Math.pow(Math.sin(dlat / 2), 2)
+                + Math.cos(lat1) * Math.cos(lat2)
+                * Math.pow(Math.sin(dlon / 2),2);          
+    let c = 2 * Math.asin(Math.sqrt(a));
+  
+    // Radius of earth in meters
+    let r = 6371000;
+    
+    // calculate the result
+    return `${(c * r).toFixed()} m`;
+}
+
 
 module.exports = {
     compare,
-    convertValue
+    convertValue,
+    distanceFrom
 };
\ No newline at end of file