On-board package hover traces from the carrier's current position (ISS-040)

lib/mapData.test.ts

@@ -1,6 +1,6 @@
 import { describe, expect, it } from 'vitest';
 import type { StateSnapshot } from './game/state';
-import { planesGeoJson, routesGeoJson, hoverRouteGeoJson, greatCircleArc, ROUTE_ARC_SEGMENTS, type AirportCoord } from './mapData';
+import { planesGeoJson, routesGeoJson, hoverRouteGeoJson, hoverTraceGeoJson, greatCircleArc, ROUTE_ARC_SEGMENTS, type AirportCoord } from './mapData';
 import { haversineKm } from './geo';
 
 const AIRPORTS = new Map<string, AirportCoord>([
@@ -176,6 +176,23 @@ describe('hoverRouteGeoJson (ISS-022/025/027 v0.22.0 — hover route trace)', ()
   });
 });
 
+describe('hoverTraceGeoJson (ISS-040 v0.23.2 — on-board package trace from the carrier\'s live position)', () => {
+  it('draws one great-circle line from the given start coord to the dest airport with exact endpoints', () => {
+    const from = { lat: 51.2, lon: 9.1 }; // a mid-flight position — not an airport
+    const fc = hoverTraceGeoJson(from, 'EHAM', AIRPORTS);
+    expect(fc.features).toHaveLength(1);
+    expect(fc.features[0].properties).toEqual({ planeId: '' }); // pure overlay — no owning plane
+    const coords = fc.features[0].geometry.coordinates;
+    expect(coords.length).toBe(ROUTE_ARC_SEGMENTS + 1); // sampled arc, not a 2-point chord
+    expect(coords[0]).toEqual([9.1, 51.2]); // live start — exact endpoint
+    expect(coords[coords.length - 1]).toEqual([4.76, 52.31]); // EHAM — exact endpoint
+  });
+
+  it('returns an empty collection when the dest airport is missing from the dataset', () => {
+    expect(hoverTraceGeoJson({ lat: 0, lon: 0 }, 'ZZZZ', AIRPORTS)).toEqual({ type: 'FeatureCollection', features: [] });
+  });
+});
+
 describe('greatCircleArc (v0.12.2 — curved route traces)', () => {
   it('samples >2 points with the endpoints exactly at the airport coords', () => {
     const arc = greatCircleArc(AIRPORTS.get('EDDF')!, AIRPORTS.get('EHAM')!);

lib/mapData.ts

@@ -112,6 +112,32 @@ export function hoverRouteGeoJson(
   };
 }
 
+// ISS-040 (v0.23.2): the on-board package hover trace — same shape as hoverRouteGeoJson but the
+// start is a live COORDINATE (the carrier plane's current position), not an airport ICAO: once the
+// plane has departed with cargo still loaded, the preview must begin where it actually is. Empty
+// collection when the destination is missing from the dataset — never guessed.
+export function hoverTraceGeoJson(
+  from: AirportCoord,
+  toIcao: string,
+  airportsByIcao: ReadonlyMap<string, AirportCoord>,
+): FeatureCollection<MapLineFeature> {
+  const to = airportsByIcao.get(toIcao);
+  if (!to) return EMPTY_LINES;
+  return {
+    type: 'FeatureCollection',
+    features: [
+      {
+        type: 'Feature',
+        geometry: {
+          type: 'LineString',
+          coordinates: greatCircleArc(from, to),
+        },
+        properties: { planeId: '' }, // no owning plane — a pure hover overlay
+      },
+    ],
+  };
+}
+
 // One LineString per FLYING plane — its current leg from locationIcao to dest_icao.
 // Grounded planes draw nothing; a flying plane missing either endpoint from the
 // dataset is skipped, never guessed. The line is sampled along the great circle