leg-aware capacity and wagon sharing

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

@@ -665,6 +665,14 @@ export function validateContainerPlacements(
   wagonPlan: WagonPlanSlot[],
   placements: ContainerPlacementInput[],
   rules?: ContainerPlacementRules,
+  /**
+   * Leg-aware occupancy (cross-leg TEU sharing): booking id → stop-index leg.
+   * With legs, a wagon's TEU/weight caps hold PER CORRIDOR EDGE — an intercity
+   * 20ft and an export 20ft coexist on one wagon when their edges allow it.
+   * Omitted → one edge, byte-identical to the whole-route check.
+   */
+  legs?: Map<string, { from: number; to: number }>,
+  edgeCount?: number,
 ): string[] {
   const violations: string[] = [];
   const units = expandBookingContainerUnits(containerBookings);
@@ -721,8 +729,18 @@ export function validateContainerPlacements(
     }
   }
 
-  const slotTeuUsed = new Map<number, number>();
-  const slotWeightUsed = new Map<number, number>();
+  // TEU and weight are tracked PER EDGE of a unit's leg; without legs there is
+  // a single edge and this is exactly the old whole-route accounting.
+  const edges = Math.max(1, edgeCount ?? 1);
+  const legOf = (bookingId: string): { from: number; to: number } => {
+    const leg = legs?.get(bookingId);
+    if (!leg || leg.from < 0 || leg.to > edges || leg.from >= leg.to) {
+      return { from: 0, to: edges };
+    }
+    return leg;
+  };
+  const slotTeuUsed = new Map<number, number[]>();
+  const slotWeightUsed = new Map<number, number[]>();
   const slotBySeq = new Map(wagonPlan.map((s) => [s.sequenceNo, s]));
 
   for (const placement of placements) {
@@ -734,22 +752,38 @@ export function validateContainerPlacements(
     if (!unit) continue;
 
     const teu = unit.teuSlots ?? teuSlotsForSizeFt(unit.sizeFt ?? 20);
-    const usedTeu = slotTeuUsed.get(placement.sequenceNo) ?? 0;
-    if (usedTeu + teu > MAX_TEU_SLOTS_PER_WAGON) {
+    const leg = legOf(unit.bookingId);
+    const teuRow =
+      slotTeuUsed.get(placement.sequenceNo) ?? new Array<number>(edges).fill(0);
+    let teuFits = true;
+    for (let e = leg.from; e < leg.to; e += 1) {
+      if ((teuRow[e] ?? 0) + teu > MAX_TEU_SLOTS_PER_WAGON) {
+        teuFits = false;
+        break;
+      }
+    }
+    if (!teuFits) {
       violations.push(
         `Wagon #${placement.sequenceNo} cannot fit another ${unit.containerTypeCode} (max 1×40ft or 2×20ft per wagon)`,
       );
     } else {
-      slotTeuUsed.set(placement.sequenceNo, usedTeu + teu);
+      for (let e = leg.from; e < leg.to; e += 1) teuRow[e] = (teuRow[e] ?? 0) + teu;
+      slotTeuUsed.set(placement.sequenceNo, teuRow);
     }
 
     const slot = slotBySeq.get(placement.sequenceNo);
     if (slot) {
-      const weight = roundTons(slotWeightUsed.get(placement.sequenceNo) ?? 0) + unit.grossWeightTons;
-      slotWeightUsed.set(placement.sequenceNo, weight);
-      if (weight > slot.capacityTons) {
+      const weightRow =
+        slotWeightUsed.get(placement.sequenceNo) ?? new Array<number>(edges).fill(0);
+      let heaviestEdge = 0;
+      for (let e = leg.from; e < leg.to; e += 1) {
+        weightRow[e] = roundTons((weightRow[e] ?? 0) + unit.grossWeightTons);
+        heaviestEdge = Math.max(heaviestEdge, weightRow[e]);
+      }
+      slotWeightUsed.set(placement.sequenceNo, weightRow);
+      if (heaviestEdge > slot.capacityTons) {
         violations.push(
-          `Wagon #${placement.sequenceNo} total container weight ${weight}T exceeds capacity ${slot.capacityTons}T`,
+          `Wagon #${placement.sequenceNo} total container weight ${heaviestEdge}T exceeds capacity ${slot.capacityTons}T`,
         );
       }
     }