allow demo users a radius around demo cities

Author: AdenForshaw

src/decorators/validate-lat-lng-user.decorator.ts

@@ -1,5 +1,19 @@
 import { Injectable, BadRequestException, ForbiddenException } from '@nestjs/common';
 
+// Helper to calculate distance between two lat/lng points in meters
+function haversineDistance(lat1: number, lng1: number, lat2: number, lng2: number): number {
+  const toRad = (x: number) => x * Math.PI / 180;
+  const R = 6371000; // meters
+  const dLat = toRad(lat2 - lat1);
+  const dLng = toRad(lng2 - lng1);
+  const a =
+    Math.sin(dLat / 2) * Math.sin(dLat / 2) +
+    Math.cos(toRad(lat1)) * Math.cos(toRad(lat2)) *
+    Math.sin(dLng / 2) * Math.sin(dLng / 2);
+  const c = 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1 - a));
+  return R * c;
+}
+
 const demoCities = [{
   "city": "New York",
   "lat": 40.7128,
@@ -28,13 +42,17 @@ export function ValidateLatLngUser(): MethodDecorator {
       const request = args[0]; // Assuming the first argument is the request object
       const lat = request?.lat;
       const lng = request?.lng;
-      const user = args[1]
+      const user = args[1];
 
       if (lat && lng && user?.isDemoAccount) {
-        //check if lat / lng is found as a demo city
-        const foundCity = demoCities.find(city => city.lat === lat && city.lng === lng);
-        if (!foundCity) {
-          throw new BadRequestException(`Demo accounts can only access demo cities. These are ${demoCities.map(city => JSON.stringify(city)).join(", ")}`);
+        // Allow within 10,000 meters of any demo city
+        const withinRadius = demoCities.some(city =>
+          haversineDistance(lat, lng, city.lat, city.lng) <= 10000
+        );
+        if (!withinRadius) {
+          throw new BadRequestException(
+            `Demo accounts can only access locations within 10,000 meters of demo cities. Demo cities: ${demoCities.map(city => JSON.stringify(city)).join(", ")}`
+          );
         }
       }