feat(reports): break charged vs actual volume down by leg

The report priced every departure against its planned origin-to-destination
corridor, so a train that worked several station-to-station moves showed one
row and one distance. Ton/Km and Vehicle-Km were then computed against that
single corridor and understated the work actually done.

The row grain is now the leg: consecutive checkpoint events at different
yards, read with lead() over each schedule. DISTINCT because a train that
works the same pair twice in one departure is still one leg — without it the
join fans the cargo out and doubles every SUM in the group. Both ends fall
back to the schedule's own corridor, so a departure with no checkpoints
logged keeps exactly the single row it had before.

Only query() joins the legs. The KPIs stay corridor-level and would count the
same cargo once per leg if they had that join.

apps/edr-freight-api/src/modules/reports/definitions/charged-vs-actual-volume.report.ts

@@ -1,5 +1,6 @@
 import { ObjectLiteral, SelectQueryBuilder } from 'typeorm';
 
+import { Yard } from '../../rule-engine/entities/yard.entity';
 import { ReportContext, ReportDefinition } from '../report.types';
 import {
   ACTUAL_TONS_EXPR,
@@ -14,14 +15,43 @@ import {
   TEU_EXPR,
   allocationLedgerQb,
   applyCategoryFilter,
+  distanceKmBetween,
 } from '../operations-classification';
 
 /**
- * Distance and empty-wagon count belong to the departure, so they are constant
- * within a group that includes `ts.id` — MAX() satisfies Postgres without
- * dragging a scalar subselect through the GROUP BY.
+ * A leg is one station-to-station move the train actually made: two consecutive
+ * checkpoints at different yards. DISTINCT because a train that works the same
+ * pair twice in one departure is still one leg — without it the join would fan
+ * the cargo out again and double every SUM in the group.
  */
-const ROUTE_KM = `MAX(${SCHEDULE_KM_EXPR})`;
+const LEGS = `(
+  SELECT DISTINCT e.train_schedule_id, e.from_yard_id, e.to_yard_id
+    FROM (
+      SELECT ev.train_schedule_id,
+             ev.yard_id AS from_yard_id,
+             lead(ev.yard_id) OVER (
+               PARTITION BY ev.train_schedule_id ORDER BY ev.occurred_at
+             ) AS to_yard_id
+        FROM freight.train_checkpoint_events ev
+       WHERE ev.deleted_at IS NULL
+    ) e
+   WHERE e.to_yard_id IS NOT NULL AND e.to_yard_id <> e.from_yard_id
+)`;
+
+/**
+ * LEFT joined, and both ends fall back to the schedule's own corridor: a
+ * departure with no checkpoints logged has no legs, and must keep the single
+ * origin-to-destination row it had before this report knew about legs.
+ */
+const LEG_FROM = 'COALESCE(leg.from_yard_id, ts.origin_station_id)';
+const LEG_TO = 'COALESCE(leg.to_yard_id, ts.destination_station_id)';
+
+/**
+ * Distance and empty-wagon count are constant within a group that includes
+ * `ts.id` and the leg — MAX() satisfies Postgres without dragging a scalar
+ * subselect through the GROUP BY.
+ */
+const LEG_KM = `MAX(${distanceKmBetween(LEG_FROM, LEG_TO)})`;
 const EMPTY_WAGONS = `MAX(${SCHEDULE_EMPTY_WAGONS})`;
 
 /**
@@ -29,8 +59,8 @@ const EMPTY_WAGONS = `MAX(${SCHEDULE_EMPTY_WAGONS})`;
  * configured distance. A missing distance is not a zero distance, and zeroing
  * it would understate the corridor's work without anyone noticing.
  */
-const TON_KM = `ROUND((${CHARGED_TONS_EXPR})::numeric * ${ROUTE_KM}, 1)::float8`;
-const VEHICLE_KM = `ROUND(${EMPTY_WAGONS}::numeric * ${ROUTE_KM}, 1)::float8`;
+const TON_KM = `ROUND((${CHARGED_TONS_EXPR})::numeric * ${LEG_KM}, 1)::float8`;
+const VEHICLE_KM = `ROUND(${EMPTY_WAGONS}::numeric * ${LEG_KM}, 1)::float8`;
 
 function baseQuery(ctx: ReportContext): SelectQueryBuilder<ObjectLiteral> {
   const qb = allocationLedgerQb(ctx);
@@ -38,22 +68,37 @@ function baseQuery(ctx: ReportContext): SelectQueryBuilder<ObjectLiteral> {
   return qb;
 }
 
+/** The row grain: one leg of one departure. Only `query()` needs it — the KPIs
+ * are corridor-level and would count the same cargo once per leg if they had
+ * this join. */
+function legQuery(ctx: ReportContext): SelectQueryBuilder<ObjectLiteral> {
+  return baseQuery(ctx)
+    .leftJoin(LEGS, 'leg', 'leg.train_schedule_id = ts.id')
+    .leftJoin(Yard, 'lfy', `lfy.id = ${LEG_FROM}`)
+    .leftJoin(Yard, 'lty', `lty.id = ${LEG_TO}`);
+}
+
 export const chargedVsActualVolumeReport: ReportDefinition = {
   key: 'charged-vs-actual-volume',
   title: 'Charged and Actual Volumes',
   description:
-    'Charged versus actual volume per train and cargo type, with Ton/Km and Vehicle-Km. ' +
-    'Charged volume is the standard weight capacity — 20 and 40 tons per laden container, ' +
-    '2.24 and 3.88 empty, 70 tons per wagon of steel or fertilizer, 38 for perishables — ' +
-    'all editable in Operating standards. Actual volume is what the marshalling recorded. ' +
-    'Vehicle-Km counts the empty wagons on that train, so it repeats across the train’s ' +
-    'cargo types rather than being split between them.',
+    'Charged versus actual volume per leg and cargo type, with Ton/Km and Vehicle-Km. ' +
+    'A leg is one station-to-station move the train actually made, read from its logged ' +
+    'checkpoints; a departure with no checkpoints logged shows as its single planned ' +
+    'corridor. Charged volume is the standard weight capacity — 20 and 40 tons per laden ' +
+    'container, 2.24 and 3.88 empty, 70 tons per wagon of steel or fertilizer, 38 for ' +
+    'perishables — all editable in Operating standards. Actual volume is what the ' +
+    'marshalling recorded. Volumes and wagon counts belong to the train, not to the leg, ' +
+    'so they repeat on every leg it ran and across its cargo types rather than being split ' +
+    'between them — the KPIs above count each train once. Ton/Km and Vehicle-Km are the ' +
+    'exception and are the leg’s own, so they add up across legs into the real corridor ' +
+    'figure.',
   group: 'Operations',
   filters: [...OPERATIONS_FILTERS, CARGO_CATEGORY_FILTER],
   columns: [
     { key: 'trainNumber', label: 'Train No.', type: 'string', sortable: true, sortExpr: 'ts.train_number' },
     { key: 'departedAt', label: 'Departure', type: 'date', sortable: true, sortExpr: 'ts.scheduled_departure_date' },
-    { key: 'station', label: 'Station', type: 'string' },
+    { key: 'leg', label: 'Leg', type: 'string' },
     { key: 'category', label: 'Cargo type', type: 'string', sortable: true, sortExpr: CARGO_CATEGORY_EXPR },
     { key: 'chargedTons', label: 'Charged volume', type: 'tons', sortable: true },
     { key: 'actualTons', label: 'Actual volume', type: 'tons', sortable: true },
@@ -66,27 +111,29 @@ export const chargedVsActualVolumeReport: ReportDefinition = {
   ],
   defaultSort: { key: 'departedAt', dir: 'DESC' },
   query(ctx) {
-    return baseQuery(ctx)
+    return legQuery(ctx)
       .select("COALESCE(ts.train_number, '—')", 'trainNumber')
       .addSelect(`to_char(COALESCE(ts.actual_departure_at, ts.scheduled_departure_date), 'YYYY-MM-DD HH24:MI')`, 'departedAt')
-      .addSelect("COALESCE(oy.label, oy.code, '?') || ' → ' || COALESCE(dy.label, dy.code, '?')", 'station')
+      .addSelect("COALESCE(lfy.label, lfy.code, '?') || ' → ' || COALESCE(lty.label, lty.code, '?')", 'leg')
       .addSelect(CARGO_CATEGORY_LABEL_EXPR, 'category')
       .addSelect(`ROUND((${CHARGED_TONS_EXPR})::numeric, 2)::float8`, 'chargedTons')
       .addSelect(`ROUND((${ACTUAL_TONS_EXPR})::numeric, 2)::float8`, 'actualTons')
       .addSelect(TEU_EXPR, 'teu')
       .addSelect(LOADED_WAGONS_EXPR, 'wagons')
       .addSelect(`${EMPTY_WAGONS}::int`, 'emptyWagons')
-      .addSelect(`${ROUTE_KM}::float8`, 'distanceKm')
+      .addSelect(`${LEG_KM}::float8`, 'distanceKm')
       .addSelect(TON_KM, 'tonKm')
       .addSelect(VEHICLE_KM, 'vehicleKm')
       .groupBy('ts.id')
       .addGroupBy('ts.train_number')
       .addGroupBy('ts.actual_departure_at')
       .addGroupBy('ts.scheduled_departure_date')
-      .addGroupBy('oy.label')
-      .addGroupBy('oy.code')
-      .addGroupBy('dy.label')
-      .addGroupBy('dy.code')
+      .addGroupBy('leg.from_yard_id')
+      .addGroupBy('leg.to_yard_id')
+      .addGroupBy('lfy.label')
+      .addGroupBy('lfy.code')
+      .addGroupBy('lty.label')
+      .addGroupBy('lty.code')
       .addGroupBy(CARGO_CATEGORY_EXPR);
   },
   async summary(ctx) {