Refactor wagon specifications to rely on wagon type; remove tare weight and max payload from wagon entity and related components

apps/edr-freight-api/src/migrations/2080000000000-DropWagonSpecColumns.ts

@@ -0,0 +1,53 @@
+import { MigrationInterface, QueryRunner } from 'typeorm';
+
+/**
+ * Wagon spec belongs to the wagon TYPE, not to each physical wagon.
+ *
+ * `wagons.tare_weight` and `wagons.max_payload_weight` duplicated
+ * `wagon_types.tare_weight_tons` / `wagon_types.capacity_tons` on all 1100 rows,
+ * with nothing keeping them in step. They had drifted completely: every wagon
+ * disagreed with its type's tare (seeded ~20T against a real 22.4T NW5), and a
+ * third disagreed on payload (NW5 wagons claiming 22T–70T against a flat 70T).
+ * None of those numbers came from the railway.
+ *
+ * Nothing reads them for capacity — that math resolves tare and capacity through
+ * `wagon_type_id` — so dropping them removes a source of fiction rather than a
+ * source of truth. `wagon_type_id` is NOT NULL with no orphans, so the type is
+ * always reachable.
+ *
+ * A wagon re-tared after repair would need a nullable override column on
+ * `wagons` falling back to the type; deliberately not added, since no such
+ * per-wagon value exists today.
+ */
+export class DropWagonSpecColumns2080000000000 implements MigrationInterface {
+  public async up(queryRunner: QueryRunner): Promise<void> {
+    await queryRunner.query(`
+      ALTER TABLE freight.wagons
+        DROP COLUMN IF EXISTS tare_weight,
+        DROP COLUMN IF EXISTS max_payload_weight;
+    `);
+  }
+
+  public async down(queryRunner: QueryRunner): Promise<void> {
+    // Re-add nullable, backfill from the owning type, then restore NOT NULL.
+    // The pre-drop values were drifted seed data and are not recoverable — the
+    // type's spec is what they should always have held.
+    await queryRunner.query(`
+      ALTER TABLE freight.wagons
+        ADD COLUMN IF NOT EXISTS tare_weight NUMERIC(10, 2),
+        ADD COLUMN IF NOT EXISTS max_payload_weight NUMERIC(10, 2);
+    `);
+    await queryRunner.query(`
+      UPDATE freight.wagons w
+         SET tare_weight = t.tare_weight_tons,
+             max_payload_weight = t.capacity_tons
+        FROM freight.wagon_types t
+       WHERE t.id = w.wagon_type_id;
+    `);
+    await queryRunner.query(`
+      ALTER TABLE freight.wagons
+        ALTER COLUMN tare_weight SET NOT NULL,
+        ALTER COLUMN max_payload_weight SET NOT NULL;
+    `);
+  }
+}