Life360 location acquisition ^& nautical distance calculation

src/location.ts

@@ -0,0 +1,75 @@
+import { env } from "@/env/server.mjs";
+// @ts-ignore
+import * as life360 from "life360-node-api";
+
+const center = {longitude: env.CENTER_LONGITUDE, latitude: env.CENTER_LATITUDE};
+const MILES_PER_NAUTICAL_MILE = 1.15078;
+const KILOMETERS_PER_MILE = 1.60934;
+
+export type Position = {
+  longitude: number;
+  latitude: number;
+};
+
+// K = Kilometers, N = Nautical Miles, M = Miles (default: M)
+export function distance(
+  a: Position,
+  b: Position,
+  unit: "K" | "N" | "M" = "M"
+) {
+  if (a.latitude == b.latitude && a.longitude == b.longitude) {
+    return 0;
+  } else {
+    const radlat1 = (Math.PI * a.latitude) / 180;
+    const radlat2 = (Math.PI * b.latitude) / 180;
+    const theta = a.longitude - b.longitude;
+    const radtheta = (Math.PI * theta) / 180;
+    let dist = Math.sin(radlat1) * Math.sin(radlat2) + Math.cos(radlat1) * Math.cos(radlat2) * Math.cos(radtheta);
+    
+      if (dist > 1)
+      dist = 1;
+
+    dist = Math.acos(dist);
+    dist = (dist * 180) / Math.PI;
+    dist = dist * 60 * MILES_PER_NAUTICAL_MILE;  // Convert to miles
+
+    // Convert to the specified unit
+    switch (unit) {
+        case "K":
+            return dist * KILOMETERS_PER_MILE;
+        case "N":
+            return dist / MILES_PER_NAUTICAL_MILE;
+        case "M":
+        default:
+            return dist;
+    }
+  }
+}
+
+/**
+ * @returns The distance in meters between me and the center
+ */
+export async function getDistance(): Promise<number> {
+    // Setup the Life360 API client
+  const client = await life360.login(
+    env.LIFE360_USERNAME,
+    env.LIFE360_PASSWORD
+  );
+
+  // Get my current location
+  const circles = await client.listCircles();
+  const myCircle = circles[0];
+  const members = await myCircle.listMembers();
+  const me = members.findById(env.LIFE360_MEMBER_ID);
+
+  // Parse my location into latitude and longitude
+  const current = {
+    latitude: parseFloat(me.location.latitude),
+    longitude: parseFloat(me.location.longitude),
+  };
+
+  // Calculate the distance between my location and the center
+  const difference = distance(current, center, "K") * 1000;
+
+  return difference;
+}