feat: implement 20ft container weight-pairing validation

- Added ContainerValidationService to handle 20ft weight-pairing logic.
- Introduced validate20ftWeightPairing utility function to check weight differences.
- Updated BookingPricingService to include overweight line details and pairing errors in price response.
- Enhanced BookingTransitionService to reject submissions with unpairable 20ft containers.
- Created ShipmentValidation interface for pre-submit validation of container contracts.
- Integrated shipment validation into the contract booking process, providing warnings for overweight containers and hard blocks for pairing errors.
- Updated front-end components to display validation results and prevent submission when errors are present.

apps/edr-freight-api/src/modules/bookings/booking-pricing.service.spec.ts

@@ -45,6 +45,7 @@ describe('BookingPricingService — domestic corridor', () => {
       {} as never,
       ratesService as never,
       exchangeService as never,
+      { validate20ftPairing: jest.fn().mockResolvedValue([]) } as never,
     );
   });
 

apps/edr-freight-api/src/modules/bookings/booking-pricing.service.ts

@@ -17,6 +17,14 @@ import {
 import { GeneratePriceResponseDto, PriceLineItemDto } from './dto/generate-price-response.dto';
 import { Booking } from './entities/booking.entity';
 import { assertBookingStatus } from './booking-status.util';
+import { ContainerValidationService } from './container-validation.service';
+
+export interface OverweightLine {
+  containerTypeCode: string;
+  totalVgmTons: number;
+  maxAllowedTons: number;
+  excessTons: number;
+}
 
 export interface ComputedPriceResult {
   lineItems: PriceLineItemDto[];
@@ -27,6 +35,7 @@ export interface ComputedPriceResult {
   priorityScore: number;
   warnings: string[];
   hardBlocked: string[];
+  overweightLines: OverweightLine[];
 }
 
 type StoredPricingBreakdown = {
@@ -67,6 +76,7 @@ export class BookingPricingService {
     private readonly containerTypesService: ContainerTypesService,
     private readonly ratesService: RatesService,
     private readonly exchangeService: ExchangeService,
+    private readonly containerValidationService: ContainerValidationService,
   ) {}
 
   async generatePrice(bookingId: string): Promise<GeneratePriceResponseDto> {
@@ -94,12 +104,19 @@ export class BookingPricingService {
       },
     } as never);
 
+    // 20ft weight-pairing preview: surfaced now so the customer sees the problem
+    // (and the overweight warning + surcharge) at the confirm step, before submit.
+    // Submit re-runs this and HARD-BLOCKS on a non-empty result.
+    const pairing = await this.containerValidationService.validate20ftPairing(booking);
+
     return {
       bookingId,
       totalAmount: computed.totalAmount,
       currency: computed.currency,
       lineItems: computed.lineItems,
       warnings: computed.warnings,
+      overweightLines: computed.overweightLines,
+      pairingErrors: pairing.map((p) => p.message),
     };
   }
 
@@ -169,6 +186,35 @@ export class BookingPricingService {
       if (rate) usedRatesMap.set(rate.id, rate);
     }
 
+    // Overweight detail for the customer: map the engine's per-line results back
+    // to the booking's container lines (same order) for code + weights. maxAllowed
+    // is derived from the line total minus the excess the engine computed.
+    const overweightLines: OverweightLine[] = [];
+    const containerLines = (booking.bookingContainers ?? []).filter(
+      (bc) => bc.containerTypeId != null,
+    );
+    for (let i = 0; i < ruleResult.containerWeightResults.length; i++) {
+      const wr = ruleResult.containerWeightResults[i];
+      if (!wr?.isOverweight) continue;
+      const line = containerLines[i];
+      const totalVgmTons = Number(line?.totalVgmTons ?? 0);
+      const excessTons = Number(wr.overweightExcessTons ?? 0);
+      let code = line?.containerSize ?? '';
+      if (line?.containerTypeId) {
+        try {
+          code = (await this.containerTypesService.findById(line.containerTypeId)).code;
+        } catch {
+          // fall back to the container size label
+        }
+      }
+      overweightLines.push({
+        containerTypeCode: code,
+        totalVgmTons,
+        maxAllowedTons: Math.max(0, totalVgmTons - excessTons),
+        excessTons,
+      });
+    }
+
     return {
       lineItems,
       totalAmount: total,
@@ -178,6 +224,7 @@ export class BookingPricingService {
       priorityScore: ruleResult.priorityScore,
       warnings: ruleResult.warnings,
       hardBlocked: ruleResult.hardBlocked,
+      overweightLines,
     };
   }
 

apps/edr-freight-api/src/modules/bookings/booking-transition.accept.spec.ts

@@ -37,6 +37,7 @@ describe('BookingTransitionService — acceptIntake validity window', () => {
       bookingsService as never,
       { isPhasedGeneralCustomsBooking: () => false } as never,
       {} as never,
+      { validate20ftPairing: jest.fn().mockResolvedValue([]) } as never,
     );
     return { service, bookingsRepository, ruleEngineService };
   }

apps/edr-freight-api/src/modules/bookings/booking-transition.clearance.spec.ts

@@ -48,6 +48,7 @@ describe('BookingTransitionService — finalizeClearance gate', () => {
       bookingsService as never,
       { isPhasedGeneralCustomsBooking: () => false } as never,
       {} as never,
+      { validate20ftPairing: jest.fn().mockResolvedValue([]) } as never,
     );
     return { service, bookingsRepository };
   }
@@ -132,6 +133,7 @@ describe('BookingTransitionService — finalizeClearance customs output gate', (
       bookingsService as never,
       { isPhasedGeneralCustomsBooking: () => false } as never,
       {} as never,
+      { validate20ftPairing: jest.fn().mockResolvedValue([]) } as never,
     );
     return { service, bookingsRepository };
   }
@@ -202,6 +204,7 @@ describe('BookingTransitionService — submitClearanceDocuments required-fields
       bookingsService as never,
       { isPhasedGeneralCustomsBooking: () => false } as never,
       {} as never,
+      { validate20ftPairing: jest.fn().mockResolvedValue([]) } as never,
     );
     return { service, bookingsRepository, filesService };
   }

apps/edr-freight-api/src/modules/bookings/booking-transition.operation.spec.ts

@@ -40,6 +40,7 @@ describe('BookingTransitionService — operation review', () => {
       bookingsService as never,
       { isPhasedGeneralCustomsBooking: () => false } as never,
       {} as never,
+      { validate20ftPairing: jest.fn().mockResolvedValue([]) } as never,
     );
     return { service, bookingsRepository, bookingBatchService };
   }

apps/edr-freight-api/src/modules/bookings/booking-transition.service.ts

@@ -16,6 +16,7 @@ import { FilesService } from '../files/files.service';
 import { FileUploadSettingsService } from '../file-upload-settings/file-upload-settings.service';
 import { BookingContractService } from './booking-contract.service';
 import { BookingPricingService } from './booking-pricing.service';
+import { ContainerValidationService } from './container-validation.service';
 import { BookingsRepository } from './bookings.repository';
 import { assertBookingStatus } from './booking-status.util';
 import { clearanceCodesForBooking } from './clearance.util';
@@ -51,6 +52,7 @@ export class BookingTransitionService {
     @Inject(forwardRef(() => ClearanceWorkflowService))
     private readonly workflowService: ClearanceWorkflowService,
         private readonly invoiceService: BookingInvoiceService,
+    private readonly containerValidationService: ContainerValidationService,
 
   ) {}
 
@@ -58,6 +60,19 @@ export class BookingTransitionService {
     return this.bookingClearanceService.isPhasedGeneralCustomsBooking(booking);
   }
 
+  /** Reject submit when the booking's 20ft containers can't be balanced onto wagons. */
+  private async assert20ftPairable(booking: Booking): Promise<void> {
+    const violations =
+      await this.containerValidationService.validate20ftPairing(booking);
+    if (violations.length) {
+      throw new BadRequestException(
+        `Cannot submit — 20ft containers cannot be paired on wagons: ${violations
+          .map((v) => v.message)
+          .join(' ')}`,
+      );
+    }
+  }
+
   async submit(bookingId: string): Promise<SubmitBookingResponseDto> {
     const booking = await this.bookingsService.findById(bookingId);
     assertBookingStatus(booking, ["DRAFT", "CHANGES_REQUESTED"]);
@@ -78,6 +93,11 @@ export class BookingTransitionService {
       requiresDirectorApproval: false,
     });
 
+    // 20ft weight-pairing hard block: two 20ft on a wagon must differ ≤ the cap.
+    // If no balanced pairing exists the booking cannot proceed (overweight only
+    // warns; this rejects). An odd leftover 20ft is fine — it goes to consolidation.
+    await this.assert20ftPairable(booking);
+
     const stored = booking.pricingBreakdown as {
       lineItems?: PriceLineItemDto[];
       totalAmount?: number;
@@ -158,6 +178,7 @@ export class BookingTransitionService {
       hardBlocked: computed.hardBlocked,
       requiresDirectorApproval: false,
     });
+    await this.assert20ftPairable(booking);
 
     await this.pricingService.createPricingSnapshots(
       bookingId,

apps/edr-freight-api/src/modules/bookings/bookings.module.ts

@@ -23,6 +23,7 @@ import { BookingsController } from './bookings.controller';
 // import { PayController } from './pay.controller';
 import { BookingsRepository } from './bookings.repository';
 import { ConsolidationService } from './consolidation.service';
+import { ContainerValidationService } from './container-validation.service';
 import { BookingsService } from './bookings.service';
 import { BookingApprovalStep } from './entities/booking-approval-step.entity';
 import { BookingCargoModifier } from './entities/booking-cargo-modifier.entity';
@@ -78,6 +79,7 @@ import { BookingContainerAllocation } from "./entities/booking-container-allocat
     BookingsService,
     BookingsRepository,
     ConsolidationService,
+    ContainerValidationService,
     BookingReferenceDataService,
     BookingPricingService,
     BookingTransitionService,

apps/edr-freight-api/src/modules/bookings/container-pairing.util.spec.ts

@@ -0,0 +1,55 @@
+import { validate20ftWeightPairing } from './container-pairing.util';
+
+describe('validate20ftWeightPairing', () => {
+  const MAX_DIFF = 10;
+
+  it('passes when a balanced pairing exists (adjacent diffs within cap)', () => {
+    // sorted: 8, 15, 18, 24 → pairs (8,15) diff 7, (18,24) diff 6 — both ≤ 10.
+    const units = [
+      { label: 'A', grossWeightTons: 24 },
+      { label: 'B', grossWeightTons: 8 },
+      { label: 'C', grossWeightTons: 18 },
+      { label: 'D', grossWeightTons: 15 },
+    ];
+    expect(validate20ftWeightPairing(units, MAX_DIFF)).toEqual([]);
+  });
+
+  it('flags a pair whose weight difference exceeds the cap', () => {
+    // sorted: 5, 25 → single pair diff 20 > 10.
+    const units = [
+      { label: 'HEAVY', grossWeightTons: 25 },
+      { label: 'LIGHT', grossWeightTons: 5 },
+    ];
+    const result = validate20ftWeightPairing(units, MAX_DIFF);
+    expect(result).toHaveLength(1);
+    expect(result[0].labels).toEqual(['LIGHT', 'HEAVY']);
+    expect(result[0].diffTons).toBe(20);
+  });
+
+  it('allows an odd leftover unit (goes to consolidation, not a violation)', () => {
+    // sorted: 10, 12, 30 → pair (10,12) diff 2 ok; 30 is the odd leftover.
+    const units = [
+      { label: 'A', grossWeightTons: 10 },
+      { label: 'B', grossWeightTons: 12 },
+      { label: 'C', grossWeightTons: 30 },
+    ];
+    expect(validate20ftWeightPairing(units, MAX_DIFF)).toEqual([]);
+  });
+
+  it('adjacent-by-weight pairing succeeds where a naive input order would fail', () => {
+    // Input order (20, 12, 22, 10) naively pairs (20,12)=8 and (22,10)=12 (fail),
+    // but sorted (10,12,20,22) pairs (10,12)=2 and (20,22)=2 — valid, so no violation.
+    const units = [
+      { label: 'A', grossWeightTons: 20 },
+      { label: 'B', grossWeightTons: 12 },
+      { label: 'C', grossWeightTons: 22 },
+      { label: 'D', grossWeightTons: 10 },
+    ];
+    expect(validate20ftWeightPairing(units, MAX_DIFF)).toEqual([]);
+  });
+
+  it('returns nothing for fewer than two units', () => {
+    expect(validate20ftWeightPairing([{ label: 'A', grossWeightTons: 30 }], MAX_DIFF)).toEqual([]);
+    expect(validate20ftWeightPairing([], MAX_DIFF)).toEqual([]);
+  });
+});

apps/edr-freight-api/src/modules/bookings/container-pairing.util.ts

@@ -0,0 +1,64 @@
+/**
+ * Booking-time 20ft weight-pairing rule.
+ *
+ * A container wagon holds two 20ft containers (2 TEU). When two 20ft ride the
+ * same wagon their gross-weight difference must not exceed `maxPairDiffTons`
+ * (global rule `max20ftPairWeightDiffTons`, default 10t) so the wagon load stays
+ * balanced. 40ft containers occupy a whole wagon alone and never pair.
+ *
+ * At booking time the customer enters every 20ft container's weight but not its
+ * wagon slot, so we auto-pair: sort the 20ft weights ascending and pair adjacent
+ * (0-1, 2-3, …). Adjacent pairing minimises the diff of every pair, so if ANY
+ * valid pairing exists this one finds it — a violation here means no balanced
+ * pairing is possible and the booking must be blocked. An odd leftover 20ft is
+ * fine: it has no partner in this booking and flows to consolidation.
+ */
+
+export interface Container20ftUnit {
+  /** Human label for messages, e.g. the container number. */
+  label: string;
+  grossWeightTons: number;
+}
+
+export interface PairingViolation {
+  message: string;
+  /** The two container labels whose pairing exceeds the diff cap. */
+  labels: [string, string];
+  diffTons: number;
+}
+
+const round2 = (n: number): number => Math.round(n * 100) / 100;
+
+/**
+ * Validate that the given 20ft units can all be paired onto wagons within the
+ * weight-difference cap. Returns one violation per over-cap adjacent pair (empty
+ * when every wagon pair is balanced or there is nothing to pair). A single
+ * leftover unit (odd count) is not a violation.
+ */
+export function validate20ftWeightPairing(
+  units: Container20ftUnit[],
+  maxPairDiffTons: number,
+): PairingViolation[] {
+  if (units.length < 2 || maxPairDiffTons == null) return [];
+
+  // Ascending by weight: adjacent pairs have the smallest possible diffs.
+  const sorted = [...units].sort((a, b) => a.grossWeightTons - b.grossWeightTons);
+  const violations: PairingViolation[] = [];
+
+  for (let i = 0; i + 1 < sorted.length; i += 2) {
+    const a = sorted[i];
+    const b = sorted[i + 1];
+    const diff = Math.abs(a.grossWeightTons - b.grossWeightTons);
+    if (diff > maxPairDiffTons) {
+      violations.push({
+        message:
+          `20ft containers ${a.label} (${round2(a.grossWeightTons)}T) and ` +
+          `${b.label} (${round2(b.grossWeightTons)}T) cannot share a wagon: ` +
+          `weight difference ${round2(diff)}T exceeds the ${maxPairDiffTons}T limit.`,
+        labels: [a.label, b.label],
+        diffTons: round2(diff),
+      });
+    }
+  }
+  return violations;
+}

apps/edr-freight-api/src/modules/bookings/container-validation.service.ts

@@ -0,0 +1,76 @@
+import { Injectable } from '@nestjs/common';
+import { InjectDataSource } from '@nestjs/typeorm';
+import { DataSource, In } from 'typeorm';
+
+import { TrainSchedulingGlobalRules } from '../train-scheduling/entities/train-scheduling-global-rules.entity';
+import { Booking } from './entities/booking.entity';
+import { BookingContainerUnit } from './entities/booking-container-unit.entity';
+import {
+  Container20ftUnit,
+  PairingViolation,
+  validate20ftWeightPairing,
+} from './container-pairing.util';
+
+/** Default 20ft pair weight-difference cap when no global rules row exists (matches the entity default). */
+const DEFAULT_MAX_20FT_PAIR_DIFF_TONS = 10;
+
+/**
+ * Booking-time container validations that need the customer-entered per-unit
+ * weights (`BookingContainerUnit`): the 20ft weight-pairing rule. Kept out of the
+ * rule engine (which works on line totals) because pairing is per physical unit.
+ */
+@Injectable()
+export class ContainerValidationService {
+  constructor(@InjectDataSource() private readonly dataSource: DataSource) {}
+
+  private async maxPairDiffTons(): Promise<number> {
+    const row = await this.dataSource
+      .getRepository(TrainSchedulingGlobalRules)
+      .find({ order: { createdAt: 'ASC' }, take: 1 })
+      .then((rows) => rows[0] ?? null)
+      .catch(() => null);
+    const v = row?.max20ftPairWeightDiffTons;
+    const n = v == null ? NaN : Number(v);
+    return Number.isFinite(n) ? n : DEFAULT_MAX_20FT_PAIR_DIFF_TONS;
+  }
+
+  /** Load every 20ft container UNIT weight for a booking (customer-entered VGM). */
+  private async load20ftUnits(booking: Booking): Promise<Container20ftUnit[]> {
+    const lines = (booking.bookingContainers ?? []).filter(
+      (bc) => (bc.containerSize ?? '').includes('20'),
+    );
+    if (!lines.length) return [];
+
+    const units = await this.dataSource
+      .getRepository(BookingContainerUnit)
+      .find({
+        where: { bookingContainerId: In(lines.map((l) => l.id)) },
+        order: { sortOrder: 'ASC' },
+      });
+
+    return units.map((u) => ({
+      label: u.containerNumber || u.id.slice(0, 8),
+      grossWeightTons: Number(u.vgmTons ?? 0),
+    }));
+  }
+
+  /**
+   * Validate the 20ft weight-pairing rule for a booking. Returns one message per
+   * pair whose weight difference exceeds the cap; empty when all 20ft can be
+   * balanced onto wagons (or there is nothing to pair). A lone odd 20ft is fine —
+   * it flows to consolidation. Callers hard-block a non-empty result.
+   */
+  async validate20ftPairing(booking: Booking): Promise<PairingViolation[]> {
+    // Only bookings whose 20ft lines actually carry per-unit weights can be
+    // checked; contract-drawdown bookings do (units are required there).
+    const containerLines = booking.bookingContainers ?? [];
+    const has20ft = containerLines.some((bc) => (bc.containerSize ?? '').includes('20'));
+    if (!has20ft) return [];
+
+    const units = await this.load20ftUnits(booking);
+    if (units.length < 2) return [];
+
+    const maxDiff = await this.maxPairDiffTons();
+    return validate20ftWeightPairing(units, maxDiff);
+  }
+}

apps/edr-freight-api/src/modules/bookings/dto/generate-price-response.dto.ts

@@ -27,6 +27,20 @@ export class PriceLineItemDto {
   currency!: string;
 }
 
+export class OverweightLineDto {
+  @ApiProperty()
+  containerTypeCode!: string;
+
+  @ApiProperty()
+  totalVgmTons!: number;
+
+  @ApiProperty()
+  maxAllowedTons!: number;
+
+  @ApiProperty()
+  excessTons!: number;
+}
+
 export class GeneratePriceResponseDto {
   @ApiProperty()
   bookingId!: string;
@@ -42,4 +56,16 @@ export class GeneratePriceResponseDto {
 
   @ApiProperty({ type: [String] })
   warnings!: string[];
+
+  /** Overweight container lines (VGM over the weight-limit rule) — surcharge already in lineItems. */
+  @ApiProperty({ type: [OverweightLineDto] })
+  overweightLines!: OverweightLineDto[];
+
+  /**
+   * 20ft weight-pairing violations. Non-empty means the booking cannot be
+   * balanced onto wagons and submit is HARD-BLOCKED — the customer must fix
+   * container weights/quantities. (Overweight, by contrast, only warns.)
+   */
+  @ApiProperty({ type: [String] })
+  pairingErrors!: string[];
 }