fix

apps/edr-freight-api/src/modules/wagons/train-runs.const.ts

@@ -0,0 +1,41 @@
+/**
+ * EDR run-number pairs, keyed by the odd EXPORT run (Ethiopia → Djibouti). The
+ * even IMPORT run (Djibouti → Ethiopia) is fixed by the export run.
+ *
+ * Run numbers are always 4 digits (8401, never 84001). Pairs are listed out
+ * rather than computed from the 8001/+100/+1 pattern, so a run that ever breaks
+ * the convention stays correct here.
+ *
+ * SeedWagonRunNumbers2280000000000 carries its own frozen copy on purpose: a
+ * migration must keep doing what it did when it was applied, whereas this list
+ * is live config for the update script. Add or retire runs HERE.
+ */
+export const TRAIN_RUN_PAIRS: Record<string, string> = {
+  '8001': '8002',
+  '8101': '8102',
+  '8201': '8202',
+  '8301': '8302',
+  '8401': '8402',
+  '8501': '8502',
+  '8601': '8602',
+  '8701': '8702',
+  '8801': '8802',
+  '8901': '8902',
+  '9001': '9002',
+};
+
+/** Even IMPORT run -> its odd EXPORT run. Derived so the two cannot drift. */
+export const EXPORT_BY_IMPORT: Record<string, string> = Object.fromEntries(
+  Object.entries(TRAIN_RUN_PAIRS).map(([exportRun, importRun]) => [importRun, exportRun]),
+);
+
+/**
+ * Normalise any run number to its EXPORT run. Accepts either half of a pair, so
+ * a sheet listing "8002" and one listing "8001" both resolve to the same train.
+ * Returns null when the number belongs to no known run.
+ */
+export const toExportRun = (run: string): string | null => {
+  const value = run.trim();
+  if (TRAIN_RUN_PAIRS[value]) return value;
+  return EXPORT_BY_IMPORT[value] ?? null;
+};