auto allocation and batch managemnt, tracking the train

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

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+/** Physical dimensions used when deriving how many wagons a locomotive can pull. */
+export type WagonTypeDimensions = {
+  lengthMeters: number;
+  capacityTons: number;
+};
+
+export type LocomotiveLimits = {
+  maxPullWeightTons: number;
+  maxTrainLengthMeters: number;
+};
+
+export type DerivedTrainCapacity = {
+  maxWeightTons: number;
+  maxLengthMeters: number;
+  maxWagonSlots: number;
+};
+
+const DEFAULT_WAGON_LENGTH_M = 14;
+const DEFAULT_WAGON_CAPACITY_T = 70;
+
+/**
+ * Derive train capacity from locomotive pull weight and train length.
+ * Wagon count is NOT a fixed 53 — it is the minimum of:
+ * - floor(maxLength / shortest wagon type length)
+ * - floor(maxWeight / lightest wagon type capacity)
+ */
+export function deriveTrainCapacityFromLocomotive(
+  locomotive: LocomotiveLimits,
+  wagonTypes: WagonTypeDimensions[],
+  ruleCaps?: { maxTrainWeightTons?: number; maxTrainLengthMeters?: number },
+): DerivedTrainCapacity {
+  const maxWeightTons = Math.min(
+    Number(locomotive.maxPullWeightTons) || Infinity,
+    ruleCaps?.maxTrainWeightTons ?? Infinity,
+  );
+  const maxLengthMeters = Math.min(
+    Number(locomotive.maxTrainLengthMeters) || Infinity,
+    ruleCaps?.maxTrainLengthMeters ?? Infinity,
+  );
+
+  const types =
+    wagonTypes.length > 0
+      ? wagonTypes
+      : [{ lengthMeters: DEFAULT_WAGON_LENGTH_M, capacityTons: DEFAULT_WAGON_CAPACITY_T }];
+
+  const minLength = Math.min(...types.map((w) => Number(w.lengthMeters) || DEFAULT_WAGON_LENGTH_M));
+  const minCapacity = Math.min(
+    ...types.map((w) => Number(w.capacityTons) || DEFAULT_WAGON_CAPACITY_T),
+  );
+
+  const byLength =
+    minLength > 0 && Number.isFinite(maxLengthMeters)
+      ? Math.floor(maxLengthMeters / minLength)
+      : 0;
+  const byWeight =
+    minCapacity > 0 && Number.isFinite(maxWeightTons)
+      ? Math.floor(maxWeightTons / minCapacity)
+      : byLength;
+
+  const maxWagonSlots = Math.max(0, Math.min(byLength, byWeight));
+
+  return {
+    maxWeightTons: Number.isFinite(maxWeightTons) ? maxWeightTons : MAX_FALLBACK_WEIGHT,
+    maxLengthMeters: Number.isFinite(maxLengthMeters) ? maxLengthMeters : MAX_FALLBACK_LENGTH,
+    maxWagonSlots,
+  };
+}
+
+export const MAX_FALLBACK_WEIGHT = 3500;
+export const MAX_FALLBACK_LENGTH = 760;
+
+/** Per-booking train length from wagon count and freight-specific wagon type length. */
+export function bookingTrainLengthMeters(
+  freightType: string | null | undefined,
+  wagonCount: number,
+  lengths: { container: number; bulk: number },
+): number {
+  const perWagon = freightType === 'BULK' ? lengths.bulk : lengths.container;
+  return wagonCount * perWagon;
+}
+
+export function wagonTypeDimensionsFromEntity(wt: {
+  lengthMeters?: number | string | null;
+  capacityTons?: number | string | null;
+}): WagonTypeDimensions {
+  return {
+    lengthMeters: Number(wt.lengthMeters) || DEFAULT_WAGON_LENGTH_M,
+    capacityTons: Number(wt.capacityTons) || DEFAULT_WAGON_CAPACITY_T,
+  };
+}