add lashing surcharge for cargo types with hasLashing flag

add lashing surcharge for cargo types with hasLashing flag

apps/edr-freight-api/src/modules/train-scheduling/wagon-plan-flex.util.spec.ts

@@ -1,6 +1,10 @@
 import { Booking } from '../bookings/entities/booking.entity';
 import { WagonType } from '../wagon-types/entities/wagon-type.entity';
-import { planWagonsWithStock } from './wagon-plan-flex.util';
+import {
+  applyWagonOrderReversal,
+  planWagonsWithStock,
+} from './wagon-plan-flex.util';
+import type { WagonPlanSlot } from './wagon-plan.util';
 
 const nw6: WagonType = {
   id: 'wt-nw6',
@@ -130,3 +134,56 @@ describe('planWagonsWithStock — shortage detail', () => {
     expect(result.deferred[0]?.shortage).toBeNull();
   });
 });
+
+describe('applyWagonOrderReversal', () => {
+  const slot = (
+    seq: number,
+    wagonTypeId: string,
+    bookingId: string,
+  ): WagonPlanSlot =>
+    ({
+      sequenceNo: seq,
+      wagonTypeId,
+      capacityTons: 70,
+      lengthMeters: 14,
+      assignedWeightTons: 25,
+      allocations: [{ bookingId }],
+    }) as unknown as WagonPlanSlot;
+
+  const plan: WagonPlanSlot[] = [
+    slot(1, 'wt-a', 'BKG-A'),
+    slot(2, 'wt-b', 'BKG-B'),
+    slot(3, 'wt-c', 'BKG-C'),
+  ];
+
+  it('returns the plan unchanged when the flag is false/absent', () => {
+    expect(applyWagonOrderReversal(plan, false)).toBe(plan);
+    expect(applyWagonOrderReversal(plan, undefined)).toBe(plan);
+    expect(applyWagonOrderReversal(plan, null)).toBe(plan);
+  });
+
+  it('flips the order and renumbers sequenceNo 1..N when the flag is true', () => {
+    const reversed = applyWagonOrderReversal(plan, true);
+    // Physically-last wagon (was seq 3, wt-c) is now position 1.
+    expect(reversed.map((s) => s.wagonTypeId)).toEqual(['wt-c', 'wt-b', 'wt-a']);
+    expect(reversed.map((s) => s.sequenceNo)).toEqual([1, 2, 3]);
+  });
+
+  it('keeps each booking with its own wagon — only the position changes', () => {
+    const reversed = applyWagonOrderReversal(plan, true);
+    // The booking that was in the last wagon now sits at sequenceNo 1.
+    expect(reversed[0].sequenceNo).toBe(1);
+    expect(
+      (reversed[0].allocations as { bookingId: string }[])[0].bookingId,
+    ).toBe('BKG-C');
+    expect(
+      (reversed[2].allocations as { bookingId: string }[])[0].bookingId,
+    ).toBe('BKG-A');
+  });
+
+  it('does not mutate the input plan', () => {
+    applyWagonOrderReversal(plan, true);
+    expect(plan.map((s) => s.sequenceNo)).toEqual([1, 2, 3]);
+    expect(plan.map((s) => s.wagonTypeId)).toEqual(['wt-a', 'wt-b', 'wt-c']);
+  });
+});