fix: v0.12.2 — ISS-003 route leg lines now follow the curved great-circle path (greatCircleArc, 25 sampled points via sim slerp) instead of a straight two-point chord; e2e asserts >2 coordinates in the routes source

lib/mapData.test.ts

@@ -1,11 +1,13 @@
 import { describe, expect, it } from 'vitest';
 import type { StateSnapshot } from './game/state';
-import { planesGeoJson, routesGeoJson, type AirportCoord } from './mapData';
+import { planesGeoJson, routesGeoJson, greatCircleArc, ROUTE_ARC_SEGMENTS, type AirportCoord } from './mapData';
+import { haversineKm } from './geo';
 
 const AIRPORTS = new Map<string, AirportCoord>([
   ['EDDF', { lat: 50.03, lon: 8.56 }],
   ['EDDV', { lat: 52.46, lon: 9.68 }],
   ['EHAM', { lat: 52.31, lon: 4.76 }],
+  ['LEMD', { lat: 40.47, lon: -3.56 }], // Madrid — ~1400 km from EDDF for the long-route test
 ]);
 
 function snapshot(overrides: Partial<StateSnapshot> = {}): StateSnapshot {
@@ -106,10 +108,10 @@ describe('routesGeoJson (v0.12.0 — one line per flying plane\'s current leg)',
     );
     expect(fc.features).toHaveLength(1);
     expect(fc.features[0].properties).toEqual({ planeId: 'p1' });
-    expect(fc.features[0].geometry.coordinates).toEqual([
-      [8.56, 50.03], // EDDF [lon, lat]
-      [4.76, 52.31], // EHAM
-    ]);
+    const coords = fc.features[0].geometry.coordinates;
+    expect(coords.length).toBe(ROUTE_ARC_SEGMENTS + 1); // sampled great-circle arc, not a 2-point chord (v0.12.2)
+    expect(coords[0]).toEqual([8.56, 50.03]); // EDDF [lon, lat] — exact endpoint
+    expect(coords[coords.length - 1]).toEqual([4.76, 52.31]); // EHAM — exact endpoint
   });
 
   it('skips a flying plane whose endpoint is missing from the airport dataset', () => {
@@ -137,3 +139,33 @@ describe('routesGeoJson (v0.12.0 — one line per flying plane\'s current leg)',
     expect(fc.features.map((f) => f.properties.planeId).sort()).toEqual(['p1', 'p2']);
   });
 });
+
+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')!);
+    expect(arc.length).toBe(ROUTE_ARC_SEGMENTS + 1); // 25 coordinates: 23 intermediate points
+    expect(arc[0]).toEqual([8.56, 50.03]); // EDDF [lon, lat]
+    expect(arc[arc.length - 1]).toEqual([4.76, 52.31]); // EHAM
+  });
+
+  it('midpoint of a long route deviates from the straight chord (it is actually curved)', () => {
+    const from = AIRPORTS.get('EDDF')!;
+    const to = AIRPORTS.get('LEMD')!; // ~1400 km — sagitta ≈ 40 km off the chord
+    const arc = greatCircleArc(from, to);
+    const mid = arc[Math.floor(arc.length / 2)]; // t = 0.5 exactly (index SEGMENTS/2)
+    const chordMid: [number, number] = [(from.lon + to.lon) / 2, (from.lat + to.lat) / 2];
+    expect(haversineKm(mid[1], mid[0], chordMid[1], chordMid[0])).toBeGreaterThan(5); // km off the straight line
+  });
+
+  it('short routes still fine: exact endpoints and a nearly-straight arc', () => {
+    const from = AIRPORTS.get('EDDF')!;
+    const to = AIRPORTS.get('EDDV')!; // ~280 km — sagitta ≈ 1.5 km, visually near-straight
+    const arc = greatCircleArc(from, to);
+    expect(arc.length).toBe(ROUTE_ARC_SEGMENTS + 1);
+    expect(arc[0]).toEqual([from.lon, from.lat]);
+    expect(arc[arc.length - 1]).toEqual([to.lon, to.lat]);
+    const mid = arc[Math.floor(arc.length / 2)];
+    const chordMid: [number, number] = [(from.lon + to.lon) / 2, (from.lat + to.lat) / 2];
+    expect(haversineKm(mid[1], mid[0], chordMid[1], chordMid[0])).toBeLessThan(5); // stays close to the chord
+  });
+});