fix(roadtrip): hand a hire car without a return day back on its pick-up day

A car booking without an end day is a one-day booking everywhere else in
the plan, but the road trip read it as a car never handed back: only its
pick-up desk stood on the road. Two one-way car bookings on one day
(Bologna to Villach, then Villach to Klagenfurt) therefore drove from the
first pick-up to the second and on to whatever came before, counting the
road between the two cities twice and never reaching Klagenfurt. This
applies to the planner, the phone and calculate_roadtrip alike, since all
three seat the desks through the shared carrierSeam.

Such a car now has its return desk on the pick-up day. A return without a
time goes back before the next car of that day is collected rather than
closing the day behind it, so each one-way car drives its own road once.
Bookings with a return day and cars without a located return desk are
unchanged.

Closes #2894

shared/src/roadtrip/carriers.spec.ts

@@ -198,9 +198,7 @@ describe('a hire car', () => {
     expect(sameDesk.arrival).toMatchObject({ name: 'Europcar MUC' });
   });
 
-  it('ROADTRIP-CARRIERS-017: a hire car without a return day or a return desk stands on the road at its pick-up only, nothing is guessed', () => {
-    const noDay = carrierSeam(rental({ end_day_id: null }))!;
-    expect(noDay.arrival).toBeNull();
+  it('ROADTRIP-CARRIERS-017: a hire car without a return desk stands on the road at its pick-up only, nothing is guessed', () => {
     const noDesk = carrierSeam(
       rental({
         endpoints: [{ role: 'from', sequence: 0, name: 'Sixt Hauptbahnhof', code: null, lat: 53.55, lng: 10.0 }],
@@ -208,11 +206,63 @@ describe('a hire car', () => {
     )!;
     expect(noDesk.arrival).toBeNull();
     expect(carrierSeam(rental({ endpoints: [] }))).toBeNull();
-    const seated = seatCarrierStops(1, [stop({ ownerIndex: 0, time: '10:00' })], [0], [noDay]);
+    const seated = seatCarrierStops(1, [stop({ ownerIndex: 0, time: '10:00' })], [0], [noDesk]);
     expect(seated.map((s) => s.carrier?.role ?? s.name)).toEqual(['pickup', 'Stop 0']);
-    expect(seatCarrierStops(3, [stop({ ownerIndex: 0 })], [0], [noDay]).map((s) => s.carrier?.role ?? s.name)).toEqual([
-      'Stop 0',
+    expect(seatCarrierStops(3, [stop({ ownerIndex: 0 })], [0], [noDesk]).map((s) => s.carrier?.role ?? s.name)).toEqual(
+      ['Stop 0'],
+    );
+  });
+
+  it('ROADTRIP-CARRIERS-036: a hire car without a return day is handed back on its pick-up day, as the day plan reads it (#2894)', () => {
+    const oneWay = carrierSeam(rental({ end_day_id: null, reservation_end_time: null }))!;
+    expect(oneWay.arrival).toMatchObject({ dayId: 1, clock: null, name: 'Sixt Airport' });
+    const seated = seatCarrierStops(1, [stop({ ownerIndex: 0, time: '10:00' })], [0], [oneWay]);
+    expect(seated.map((s) => s.carrier?.role ?? s.name)).toEqual(['pickup', 'Stop 0', 'return']);
+  });
+
+  it('ROADTRIP-CARRIERS-037: two one-way cars on one day: the first goes back before the second is collected, and the road runs once through each', () => {
+    const desk = (role: 'from' | 'to', name: string, lat: number, lng: number) => ({
+      role,
+      sequence: role === 'from' ? 0 : 1,
+      name,
+      code: null,
+      lat,
+      lng,
+    });
+    const bologna = desk('from', 'Bologna', 44.49, 11.34);
+    const villach = { lat: 46.61, lng: 13.85 };
+    const outward = carrierSeam(
+      rental({
+        id: 1,
+        title: 'Bologna → Villach',
+        end_day_id: null,
+        reservation_time: '2026-11-02T08:00',
+        reservation_end_time: null,
+        endpoints: [bologna, desk('to', 'Villach', villach.lat, villach.lng)],
+      }),
+    )!;
+    const onward = carrierSeam(
+      rental({
+        id: 2,
+        title: 'Villach → Klagenfurt',
+        end_day_id: null,
+        reservation_time: '2026-11-02T17:30',
+        reservation_end_time: null,
+        endpoints: [desk('from', 'Villach', villach.lat, villach.lng), desk('to', 'Klagenfurt', 46.62, 14.31)],
+      }),
+    )!;
+    const event = stop({ ownerIndex: 0, name: 'CUAS', lat: villach.lat, lng: villach.lng, time: '13:00' });
+
+    const seated = seatCarrierStops(1, [event], [0], [onward, outward]);
+
+    expect(seated.map((s) => `${s.carrier?.role ?? 'stop'} ${s.name}`)).toEqual([
+      'pickup Bologna',
+      'stop CUAS',
+      'return Villach',
+      'pickup Villach',
+      'return Klagenfurt',
     ]);
+    expect(seated.map((s) => s.carrier?.reservationId ?? null)).toEqual([1, null, 1, 2, 2]);
   });
 
   it('ROADTRIP-CARRIERS-018: the pick-up opens its day when nothing timed comes first, the return closes its day, and the road runs through both', () => {

shared/src/roadtrip/carriers.ts

@@ -111,8 +111,8 @@ export interface CarrierSeam {
   departure: CarrierEnd;
   /**
    * A ride always has both ends. A hire car has a return only when the booking says
-   * when and where: without a return day or a located return desk, nothing is guessed
-   * and only the pick-up stands on the road.
+   * where: without a located return desk, nothing is guessed and only the pick-up stands
+   * on the road.
    */
   arrival: CarrierEnd | null;
 }
@@ -220,9 +220,12 @@ export function carrierSeam(booking: CarrierBooking): CarrierSeam | null {
   const last = legs[legs.length - 1];
   const depDayId = departureDayOf(booking, legs);
   if (depDayId == null) return null;
-  // A ride lands on the day it left unless the booking says otherwise. A hire car is
-  // handed back on the day the booking names, and on no day when it names none.
-  const arrDayId = last?.arr_day_id ?? booking.end_day_id ?? (kind === 'ride' ? depDayId : null);
+  // A booking without an end day ends on the day it starts, as the day plan reads it
+  // (`getSpanPhase`): a ride lands there and a hire car is handed back there. Read as
+  // a car never handed back, a one-way drive between two cities kept only its pick-up,
+  // and the road ran from that desk to the next car's instead of to its own return
+  // desk (#2894).
+  const arrDayId = last?.arr_day_id ?? booking.end_day_id ?? depDayId;
   const depClock = carrierClock(first?.dep_time ?? booking.reservation_time);
   const arrClock = carrierClock(last?.arr_time ?? booking.reservation_end_time);
   const bookingPosition = (dayId: number): number | null =>
@@ -597,11 +600,30 @@ export function seatCarrierStops(
     minutes: item.minutes,
     point: item.kind === 'stop' ? { lat: stops[item.index]!.lat, lng: stops[item.index]!.lng } : null,
   });
+  // Just ahead of the next car's pick-up behind this car's own, or null when no car
+  // follows and the return closes the day. Closing the day, the first of two one-way
+  // cars was handed back after the second was collected.
+  const handOverKey = (seam: CarrierSeam): number | null => {
+    const pickups = items.filter(
+      (item): item is Extract<Item, { kind: 'end' }> => item.kind === 'end' && item.role === 'pickup',
+    );
+    const own = pickups.find((item) => item.seam === seam);
+    if (!own) return null;
+    const next = pickups.filter((item) => item.seam !== seam && item.key > own.key).map((item) => item.key);
+    return next.length ? Math.min(...next) - 0.0001 : null;
+  };
+  // A car handed back on the day it was picked up, at no stated hour, is seated once every
+  // other desk of the day is: it goes back before the next car is collected (`handOverKey`).
+  const untimedSameDayReturn = (e: { seam: CarrierSeam; role: CarrierTerminal['role']; minutes: number | null }) =>
+    e.role === 'return' && e.minutes === null && e.seam.departure.dayId === dayId;
   ends
     .map((e) => ({ ...e, minutes: parseClock(e.end.clock) }))
-    .sort((a, b) => (a.minutes ?? 0) - (b.minutes ?? 0))
+    .sort(
+      (a, b) =>
+        Number(untimedSameDayReturn(a)) - Number(untimedSameDayReturn(b)) || (a.minutes ?? 0) - (b.minutes ?? 0),
+    )
     .forEach((e, ti) => {
-      let key = e.end.position;
+      let key = e.end.position ?? (untimedSameDayReturn(e) ? handOverKey(e.seam) : null);
       if (key === null) {
         const minutes = e.minutes ?? 0;
         let after = -Infinity;

wiki/Road-Trip.md

@@ -332,7 +332,7 @@ What the seam does not do: it never plans the ride itself, and a booking without
 
 ### Hire cars
 
-A **Car** booking is not a seam, you drive it, but its desks are where the drive starts and ends. The pick-up desk stands on the day card as a row with the car icon and *Pick-up 09:00* under its name, and it opens the day when nothing timed comes before it. The return desk closes the day it is handed back on, with *Return 11:30*. The road runs through both like any other stop, the range budget starts from a full tank at the pick-up, and both rows open the booking. The return only appears when the booking names a return day and a located return desk; nothing is guessed.
+A **Car** booking is not a seam, you drive it, but its desks are where the drive starts and ends. The pick-up desk stands on the day card as a row with the car icon and *Pick-up 09:00* under its name, and it opens the day when nothing timed comes before it. The return desk closes the day it is handed back on, with *Return 11:30*. The road runs through both like any other stop, the range budget starts from a full tank at the pick-up, and both rows open the booking. The return only appears when the booking has a located return desk; nothing is guessed. A booking without a return day is handed back on the day it is picked up, as **Days** shows it, so two one-way cars on one day each drive their own road, and one handed back without a time goes back before the next car of that day is picked up.
 
 ### Other bookings on the day