Add a flight arc on the map for flights with same departing and arrival airport

resources/js/Components/FlightsGoneBy/FlightMap.vue

@@ -370,10 +370,34 @@ export default defineComponent({
             link.click()
         }
 
+        function loopPoints(origin: LngLat, radiusDeg = 0.2, steps = 48): LngLat[] {
+            const [lng, lat] = origin
+
+            // Widen the longitude radius to compensate for mercator distortion at this latitude
+            const lngRadius = radiusDeg / Math.max(Math.cos(lat * Math.PI / 180), 0.15)
+
+            // Center the loop above the origin so the airport point sits at the bottom of the loop
+            const centerLat = lat + radiusDeg
+
+            const points: LngLat[] = []
+            for (let i = 0; i <= steps; i++) {
+                const theta = (i / steps) * Math.PI * 2
+                points.push([
+                    lng + Math.sin(theta) * lngRadius,
+                    centerLat - radiusDeg * Math.cos(theta),
+                ])
+            }
+            return points // first and last point === origin, at the bottom of the loop
+        }
+
         const getArc = (flight: Flight): LngLat[] => {
             const key = routeKey(flight.departure_airport, flight.arrival_airport)
             if (!arcCache.has(key)) {
-                arcCache.set(key, greatCirclePoints(
+                const isSameAirport = flight.departure_airport.id === flight.arrival_airport.id
+
+                arcCache.set(key, isSameAirport
+                    ? loopPoints([flight.departure_airport.longitude_deg, flight.departure_airport.latitude_deg])
+                    : greatCirclePoints(
                         [flight.departure_airport.longitude_deg, flight.departure_airport.latitude_deg],
                         [flight.arrival_airport.longitude_deg,   flight.arrival_airport.latitude_deg],
                     ))
@@ -666,8 +690,10 @@ export default defineComponent({
                 ? { top: 20, bottom: 20, left: 55, right: 55 }
                 : { top: 60, bottom: 60, left: 60, right: 60 }
 
-            const lngs = props.flights.flatMap(f => [f.departure_airport.longitude_deg, f.arrival_airport.longitude_deg])
+            // Use full arc/loop geometry, not just endpoints, so loops aren't clipped
-            const lats = props.flights.flatMap(f => [f.departure_airport.latitude_deg,  f.arrival_airport.latitude_deg])
+            const allPoints = props.flights.flatMap(getArc)
+            const lngs = allPoints.map(p => p[0])
+            const lats = allPoints.map(p => p[1])
 
             const minLat = Math.min(...lats)
             const maxLat = Math.max(...lats)
@@ -689,7 +715,6 @@ export default defineComponent({
             }
             map!.fitBounds([[minLng, minLat], [maxLng, maxLat]], { padding, duration: 0 })
         }
-
         // ── Map init ──────────────────────────────────────────────────────────
 
         const initMap = (): void => {