import {
  BadRequestException,
  ConflictException,
  forwardRef,
  Inject,
  Injectable,
  Logger,
  NotFoundException,
} from '@nestjs/common';
import { Freight, NotificationAudience, NotificationType } from '@edr/types';
import { DataSource, EntityManager, In } from 'typeorm';

import { BillingService } from '../billing/billing.service';
import { ContractBookingService } from '../contracts/contract-booking.service';
import { ClearanceMilestoneService } from '../contracts/clearance-milestone.service';
import { CreateBookingUnderContractDto } from '../contracts/dto/create-booking-under-contract.dto';
import { ClearanceMilestone } from '../contracts/entities/clearance-milestone.entity';
import { FirstMileService } from '../first-mile/first-mile.service';
import { NotificationInboxService } from '../notification-inbox/notification-inbox.service';
import { wagonsPerUnitForSize } from '../rule-engine/container-type.util';
import { Rate } from '../rule-engine/entities/rate.entity';
import { BookingBatchService } from '../train-scheduling/booking-batch.service';
import { TrainSchedulingService } from '../train-scheduling/train-scheduling.service';
import { WagonAllocationBulkLoad } from '../train-schedules/entities/wagon-allocation-bulk-load.entity';
import { WagonAllocationContainerItem } from '../train-schedules/entities/wagon-allocation-container-item.entity';
import { WagonBookingAllocation } from '../train-schedules/entities/wagon-booking-allocation.entity';
import { FREIGHT_PERMS } from '../../seed/freight-permissions.registry';
import {
  BookingWagonCancellationsRepository,
  WagonCancellationListFilter,
} from './booking-wagon-cancellations.repository';
import { BookingsRepository } from './bookings.repository';
import {
  RebookCancelledWagonsDto,
  RequestWagonCancellationDto,
} from './dto/wagon-cancellation.dto';
import { Booking } from './entities/booking.entity';
import { BookingContainer } from './entities/booking-container.entity';
import { BookingContainerUnit } from './entities/booking-container-unit.entity';
import {
  BookingWagonCancellation,
  CancelledQuantities,
  CancelledUnitSnapshot,
} from './entities/booking-wagon-cancellation.entity';

/**
 * rates.rate_type of the cancellation fee — an existing rate-engine type
 * (trigger CANCELLATION, never auto-applied to booking pricing). Staff
 * configure it in the normal rates UI; the wagon flow requires the PER_WAGON
 * unit so the fee scales with the cancelled wagon count.
 */
export const WAGON_CANCELLATION_FEE_RATE_TYPE = 'CANCELLATION_FEE';
/** invoices.type of the fee invoice — the settlement branch key in BookingInvoiceService. */
export const WAGON_CANCEL_FEE_INVOICE_TYPE = 'WAGON_CANCEL_FEE';

const round2 = (n: number): number => Math.round(n * 100) / 100;
const round3 = (n: number): number => Math.round(n * 1000) / 1000;

interface RequestedCut {
  wagons: number;
  weightTons: number;
  quantities: CancelledQuantities;
}

/**
 * Partial wagon cancellation on a PAID booking, with a rebooking credit.
 *
 * Lifecycle (one ledger row per cycle, see BookingWagonCancellation):
 *  T1 request  — validate + price the fee, open the fee invoice. Nothing else
 *                moves: the wagons stay allocated until the fee is money.
 *  T2 fee paid — reduce the booking in place (applySplit mechanics: soft-delete
 *                the cut units LIFO), release the surplus wagon allocations,
 *                snapshot the cut units on the ledger row → CREDIT_AVAILABLE.
 *  T3 rebook   — customer picks a day only. The credit becomes a REAL booking
 *                via ContractBookingService.createUnderContract (which re-checks
 *                contract validity + caps), immediately marked PAID — the
 *                freight was paid on the original booking; only the fee was new
 *                money. Clearance milestones are copied from the source booking
 *                (the cargo is already cleared; clearance follows cargo, not
 *                train date).
 *
 * The cycle is repeatable by construction: the rebooked booking is a normal
 * PAID booking, so it can itself be partially cancelled again.
 */
@Injectable()
export class BookingWagonCancellationService {
  private readonly logger = new Logger(BookingWagonCancellationService.name);

  constructor(
    private readonly dataSource: DataSource,
    private readonly repo: BookingWagonCancellationsRepository,
    private readonly bookingsRepository: BookingsRepository,
    private readonly billing: BillingService,
    @Inject(forwardRef(() => ContractBookingService))
    private readonly contractBooking: ContractBookingService,
    @Inject(forwardRef(() => ClearanceMilestoneService))
    private readonly clearanceMilestones: ClearanceMilestoneService,
    @Inject(forwardRef(() => BookingBatchService))
    private readonly bookingBatch: BookingBatchService,
    @Inject(forwardRef(() => TrainSchedulingService))
    private readonly trainScheduling: TrainSchedulingService,
    @Inject(forwardRef(() => FirstMileService))
    private readonly firstMile: FirstMileService,
    private readonly inbox: NotificationInboxService,
  ) {}

  // ── T1: request ────────────────────────────────────────────────────────────

  /** Fee/credit preview for the confirm dialog — same math as the request, no writes. */
  async previewCancellation(
    bookingId: string,
    dto: RequestWagonCancellationDto,
  ): Promise<{
    wagons: number;
    weightTons: number;
    feePerWagon: number;
    feeAmount: number;
    feeCurrency: string;
    creditAmount: number;
  }> {
    const booking = await this.loadCancellableBooking(bookingId);
    const cut = await this.resolveRequestedCut(booking, dto);
    const rate = await this.feeRate();
    const feeAmount = round2(Number(rate.rateValue) * cut.wagons);
    return {
      wagons: cut.wagons,
      weightTons: cut.weightTons,
      feePerWagon: Number(rate.rateValue),
      feeAmount,
      feeCurrency: rate.currency,
      creditAmount: this.creditFor(booking, cut.wagons),
    };
  }

  async requestCancellation(
    bookingId: string,
    dto: RequestWagonCancellationDto,
    userId?: string,
  ): Promise<BookingWagonCancellation> {
    const booking = await this.loadCancellableBooking(bookingId);
    const open = await this.repo.findOpenForBooking(bookingId);
    if (open) {
      throw new ConflictException(
        'This booking already has a cancellation awaiting its fee. Pay or withdraw it first.',
      );
    }

    const cut = await this.resolveRequestedCut(booking, dto);
    const rate = await this.feeRate();
    const feeAmount = round2(Number(rate.rateValue) * cut.wagons);
    const creditAmount = this.creditFor(booking, cut.wagons);

    const row = await this.repo.create({
      bookingId,
      wagonsCancelled: cut.wagons,
      weightTons: cut.weightTons,
      cancelledQuantities: cut.quantities,
      creditAmount,
      feeRateId: rate.id,
      feeAmount,
      feeCurrency: rate.currency,
      status: 'FEE_PENDING',
      reason: dto.reason ?? null,
      requestedByUserId: userId ?? null,
    });

    // The fee invoice rides the booking's own invoice list (source=booking), so
    // the portal's existing invoice/pay stack picks it up with zero new payment
    // code. Settlement branches on type in BookingInvoiceService.
    const invoice = await this.billing.generateInvoice({
      source: Freight.InvoiceSource.Booking,
      sourceId: bookingId,
      type: WAGON_CANCEL_FEE_INVOICE_TYPE,
      companyId: booking.companyId,
      companyProfileId: booking.companyProfileId,
      currency: rate.currency,
      lines: [
        {
          chargeType: 'CANCELLATION_FEE',
          description: `Wagon cancellation fee — ${cut.wagons} wagon(s) of booking ${booking.reference}`,
          quantity: cut.wagons,
          unitRate: Number(rate.rateValue),
          amount: feeAmount,
          currency: rate.currency,
          metadata: { wagonCancellationId: row.id },
        },
      ],
      totalAmount: feeAmount,
      status: Freight.InvoiceStatus.Issued,
    });
    let updated = await this.repo.update(row.id, { feeInvoiceId: invoice.id });

    // Policy: the cancelled wagons leave the schedule NOW — capacity frees for
    // other customers immediately; the fee is still owed before the credit can
    // be rebooked. A withdraw/void re-allocates (or errors when the train has
    // no room left). If this release fails, T2 releases instead (flag unset).
    try {
      const released = await this.releaseAtRequest(bookingId, cut);
      if (released) {
        updated = await this.repo.update(row.id, {
          cancelledQuantities: { ...cut.quantities, releasedAtRequest: true },
        });
      }
    } catch (err) {
      this.logger.error(
        `Request-time wagon release failed for cancellation ${row.id}: ${err instanceof Error ? err.message : String(err)}`,
      );
    }

    this.notifyStaff(
      booking,
      'Wagon cancellation requested',
      `${booking.reference}: customer asked to cancel ${cut.wagons} wagon(s); fee invoice ${invoice.invoiceNumber} issued.`,
    );
    return updated ?? row;
  }

  /**
   * Void a FEE_PENDING request (customer withdraw or staff void). The wagons
   * left the schedule at request time, so voiding must first put them back:
   * the schedule's auto-allocation is re-run and the result verified — if the
   * train has no room left, the void FAILS with a clear error and the request
   * stays FEE_PENDING (pay the fee and rebook the credit instead).
   */
  async withdraw(cancellationId: string): Promise<BookingWagonCancellation> {
    const row = await this.mustFind(cancellationId);
    if (row.status !== 'FEE_PENDING') {
      throw new BadRequestException(
        `Only a fee-pending cancellation can be withdrawn (status is ${row.status}).`,
      );
    }

    if (row.cancelledQuantities.releasedAtRequest) {
      const booking = await this.bookingsRepository.findById(row.bookingId);
      const scheduleId = booking?.trainScheduleId;
      if (booking && scheduleId) {
        try {
          await this.trainScheduling.tryAutoWagonAllocation(scheduleId);
        } catch (err) {
          this.logger.warn(
            `Re-allocation on withdraw failed for booking ${row.bookingId}: ${err instanceof Error ? err.message : String(err)}`,
          );
        }
        // ponytail: allocation rows ≈ wagons (20ft pairs share one row/wagon);
        // switch to a weight-based check if mixed loads ever make this lie.
        const rows = await this.dataSource.getRepository(WagonBookingAllocation).count({
          where: { bookingId: row.bookingId },
        });
        if (rows < Math.round(Number(booking.wagonsRequired ?? 0))) {
          throw new ConflictException(
            'The train has no free wagon space left to restore the cancelled wagons — the request cannot be withdrawn. Pay the cancellation fee and rebook the credit on another day instead.',
          );
        }
      }
    }

    if (row.feeInvoiceId) await this.billing.cancelInvoice(row.feeInvoiceId);
    return (await this.repo.update(row.id, { status: 'WITHDRAWN' }))!;
  }

  // ── T2: fee settled ─────────────────────────────────────────────────────────

  /**
   * The fee invoice settled — reduce the booking and free the wagons. Called
   * from BookingInvoiceService's paid handler. Idempotent: a duplicate webhook
   * finds the row already past FEE_PENDING and returns.
   */
  async onFeePaid(feeInvoiceId: string): Promise<void> {
    const row = await this.repo.findByFeeInvoiceId(feeInvoiceId);
    if (!row) {
      this.logger.warn(`No wagon cancellation for paid fee invoice ${feeInvoiceId}.`);
      return;
    }
    if (row.status !== 'FEE_PENDING') return;

    // The fee can settle after loading started (slow payment). Never cut
    // loaded cargo: leave the row FEE_PENDING and alert staff to resolve
    // (reschedule the cut or refund the fee by hand). Skipped when the wagons
    // already left the schedule at request time — loading of the KEPT wagons
    // is then irrelevant to this cut.
    const releasedEarly = !!row.cancelledQuantities.releasedAtRequest;
    const bookingNow = await this.bookingsRepository.findById(row.bookingId);
    const movingNow = releasedEarly
      ? 0
      : await this.dataSource.getRepository(WagonBookingAllocation).count({
          where: { bookingId: row.bookingId, status: In(['LOADED', 'DEPARTED']) },
        });
    if (!releasedEarly && (bookingNow?.loadedAt || movingNow > 0)) {
      this.logger.error(
        `Wagon cancellation ${row.id}: fee paid but loading already started on booking ${row.bookingId} — left FEE_PENDING for manual resolution.`,
      );
      if (bookingNow) {
        this.notifyStaff(
          bookingNow,
          'Wagon cancellation fee paid after loading started',
          `${bookingNow.reference}: the customer paid the cancellation fee for ${row.wagonsCancelled} wagon(s), but loading has already started. Resolve manually (adjust the cut or refund the fee).`,
        );
      }
      return;
    }

    await this.dataSource.transaction(async (manager) => {
      const booking = await manager.getRepository(Booking).findOne({
        where: { id: row.bookingId },
        lock: { mode: 'pessimistic_write' },
      });
      if (!booking) throw new NotFoundException(`Booking ${row.bookingId} not found.`);

      const quantities = { ...row.cancelledQuantities };
      let droppedWeight = 0;

      if (quantities.bySize && Object.keys(quantities.bySize).length) {
        // Specific-wagon requests already carry the exact unit snapshots;
        // quantity requests trim LIFO and snapshot here.
        const units = quantities.units?.length
          ? await this.reduceContainerUnitsExact(manager, booking, quantities.units)
          : await this.reduceContainerLines(manager, booking, quantities.bySize);
        quantities.units = units;
        droppedWeight = round3(units.reduce((s, u) => s + Number(u.vgmTons || 0), 0));
        if (!releasedEarly) {
          await this.releaseContainerAllocations(
            manager,
            booking.id,
            units.map((u) => u.containerNumber),
          );
        }
      } else {
        droppedWeight = Number(quantities.bulkTons ?? row.weightTons);
        await this.reduceBulk(manager, booking, droppedWeight);
        if (!releasedEarly) {
          await this.releaseBulkAllocations(
            manager,
            booking.id,
            Number(row.wagonsCancelled),
            quantities.allocationIds,
          );
        }
      }

      // Mirror applySplit's bookkeeping: preSplitQuantities feeds the ONE_TIME
      // exact-remainder assertion at rebook time; isSplit releases the
      // single-active-booking slot so the rebooked booking may be created.
      const preSplitQuantities =
        booking.preSplitQuantities ?? (await this.currentQuantities(manager, booking, droppedWeight));

      await manager.getRepository(Booking).update(booking.id, {
        wagonsRequired: round2(Number(booking.wagonsRequired ?? 0) - Number(row.wagonsCancelled)),
        cargoTotalWeightVgm: round3(Number(booking.cargoTotalWeightVgm) - droppedWeight),
        totalAmount: round2(Number(booking.totalAmount) - Number(row.creditAmount)),
        isSplit: true,
        preSplitQuantities,
      } as never);

      await manager.getRepository(BookingWagonCancellation).update(row.id, {
        status: 'CREDIT_AVAILABLE',
        feePaidAt: new Date(),
        weightTons: droppedWeight,
        cancelledQuantities: quantities,
      });
    });

    const booking = await this.bookingsRepository.findById(row.bookingId);
    if (booking) {
      this.notifyCustomer(
        booking,
        'Wagon cancellation confirmed',
        `${row.wagonsCancelled} wagon(s) of ${booking.reference} are cancelled. Your paid freight is kept as credit — rebook any day while your contract is valid.`,
      );
    }
    this.logger.log(
      `Wagon cancellation ${row.id}: fee paid, booking ${row.bookingId} reduced by ${row.wagonsCancelled} wagon(s).`,
    );
  }

  // ── T3: rebook ──────────────────────────────────────────────────────────────

  async rebook(
    cancellationId: string,
    dto: RebookCancelledWagonsDto,
    userId?: string,
  ): Promise<{ cancellation: BookingWagonCancellation; bookingId: string }> {
    const row = await this.mustFind(cancellationId);
    if (row.status !== 'CREDIT_AVAILABLE') {
      throw new BadRequestException(
        `This credit cannot be rebooked (status is ${row.status}).`,
      );
    }
    const source = await this.bookingsRepository.findById(row.bookingId);
    if (!source) throw new NotFoundException(`Booking ${row.bookingId} not found.`);
    if (!source.contractId) {
      throw new BadRequestException('The original booking has no contract to rebook under.');
    }
    // Friendly pre-check; createUnderContract re-asserts inside its own guards.
    if (
      source.contractValidUntil &&
      new Date(source.contractValidUntil).getTime() < Date.now()
    ) {
      throw new BadRequestException(
        'Contract validity has expired — ask EDR staff to extend the contract before rebooking.',
      );
    }

    const createDto = this.buildRebookDto(row, dto.scheduledDate);
    const created = await this.contractBooking.createUnderContract(
      source.contractId,
      createDto,
      { id: userId ?? source.createdByUserId ?? undefined },
      // System actor: carries the create-booking key so the GL gate passes on
      // Path B (customs-clearance) contracts; harmless on Path A.
      { permissions: [{ key: FREIGHT_PERMS.contracts.createBooking }] },
    );
    const newBookingId = created.booking.id;

    // The freight is already paid (credit) — mark PAID and let the existing
    // paid-booking machinery place it. No invoice is generated for it.
    await this.dataSource.getRepository(Booking).update(newBookingId, {
      paymentStatus: 'PAID',
      status: 'PAID',
    });
    await this.copyClearanceState(source, newBookingId);

    try {
      await this.firstMile.acceptBooking(newBookingId);
    } catch (err) {
      this.logger.error(
        `First-mile accept failed for rebooked ${newBookingId}: ${err instanceof Error ? err.message : String(err)}`,
      );
    }
    try {
      await this.bookingBatch.ensurePaidBookingAllocated(newBookingId);
    } catch (err) {
      this.logger.error(
        `Allocation failed for rebooked ${newBookingId}: ${err instanceof Error ? err.message : String(err)}`,
      );
    }

    const updated = (await this.repo.update(row.id, {
      status: 'REBOOKED',
      rebookedBookingId: newBookingId,
      rebookedAt: new Date(),
    }))!;

    this.notifyCustomer(
      source,
      'Cancelled wagons rebooked',
      `Your ${row.wagonsCancelled} cancelled wagon(s) from ${source.reference} are rebooked for ${dto.scheduledDate}. No new freight charge — your credit covered it.`,
      newBookingId,
    );
    return { cancellation: updated, bookingId: newBookingId };
  }

  // ── History ────────────────────────────────────────────────────────────────

  list(filter: WagonCancellationListFilter) {
    return this.repo.list(filter);
  }

  findById(id: string): Promise<BookingWagonCancellation> {
    return this.mustFind(id);
  }

  // ── internals ──────────────────────────────────────────────────────────────

  private async mustFind(id: string): Promise<BookingWagonCancellation> {
    const row = await this.repo.findById(id);
    if (!row) throw new NotFoundException(`Wagon cancellation ${id} not found.`);
    return row;
  }

  /** PAID booking, not yet moving, with a contract to rebook under later. */
  private async loadCancellableBooking(bookingId: string): Promise<Booking> {
    const booking = await this.bookingsRepository.findById(bookingId);
    if (!booking) throw new NotFoundException(`Booking ${bookingId} not found.`);
    if (booking.paymentStatus !== 'PAID' || booking.status !== 'PAID') {
      throw new BadRequestException(
        'Only a paid booking can cancel wagons. Before payment, cancel the booking itself — no fee applies.',
      );
    }
    if (!booking.contractId) {
      throw new BadRequestException(
        'Wagon cancellation needs a contract booking (the credit is rebooked under the contract).',
      );
    }
    // Cancellation is allowed strictly BEFORE loading/dispatch: both signals
    // checked — per-wagon allocation status and the booking-level loading stamp
    // (some flows confirm loading on the booking without flipping allocations).
    if (booking.loadedAt) {
      throw new BadRequestException(
        'Cargo loading is confirmed for this booking — wagons can no longer be cancelled.',
      );
    }
    const moving = await this.dataSource.getRepository(WagonBookingAllocation).count({
      where: { bookingId, status: In(['LOADED', 'DEPARTED']) },
    });
    if (moving > 0) {
      throw new BadRequestException(
        'Loading has started for this booking — wagons can no longer be cancelled.',
      );
    }
    return booking;
  }

  /** Validate the requested cut against the live booking and size it in wagons/tons. */
  private async resolveRequestedCut(
    booking: Booking,
    dto: RequestWagonCancellationDto,
  ): Promise<RequestedCut> {
    const totalWagons = Number(booking.wagonsRequired ?? 0);
    if (totalWagons <= 0) {
      throw new BadRequestException('This booking has no wagon requirement to cancel from.');
    }

    if (dto.wagonAllocationIds?.length) {
      return this.resolveCutFromAllocations(booking, dto.wagonAllocationIds, totalWagons);
    }

    if (booking.freightType === 'CONTAINER') {
      if (!dto.containers?.length) {
        throw new BadRequestException('Specify the container units to cancel per size.');
      }
      const lines = await this.dataSource.getRepository(BookingContainer).find({
        where: { bookingId: booking.id },
      });
      const liveBySize = new Map<string, number>();
      for (const line of lines) {
        const size = line.containerSize ?? '';
        liveBySize.set(size, (liveBySize.get(size) ?? 0) + Number(line.quantity ?? 0));
      }
      const bySize: Record<string, number> = {};
      let wagons = 0;
      for (const cut of dto.containers) {
        const live = liveBySize.get(cut.containerSize) ?? 0;
        if (cut.quantity > live) {
          throw new BadRequestException(
            `Cannot cancel ${cut.quantity} × ${cut.containerSize}ft — the booking only has ${live}.`,
          );
        }
        bySize[cut.containerSize] = cut.quantity;
        wagons += cut.quantity * wagonsPerUnitForSize(Number(cut.containerSize));
      }
      wagons = round2(wagons);
      if (wagons >= totalWagons) {
        throw new BadRequestException(
          'That would cancel the whole booking — use booking cancellation instead of a partial wagon cancel.',
        );
      }
      // Snapshot the LIFO-picked physical units up front (read-only — cargo is
      // cut only when the fee settles) so the wagons carrying them can be
      // released from the schedule at request time and the portal can show
      // which containers are leaving.
      const unitRepo = this.dataSource.getRepository(BookingContainerUnit);
      const units: CancelledUnitSnapshot[] = [];
      let requested = 0;
      for (const cut of dto.containers) {
        requested += cut.quantity;
        let need = cut.quantity;
        const sizeLines = lines
          .filter((l) => (l.containerSize ?? '') === cut.containerSize)
          .sort((a, b) => +new Date(b.createdAt) - +new Date(a.createdAt));
        for (const line of sizeLines) {
          if (need <= 0) break;
          const us = await unitRepo.find({
            where: { bookingContainerId: line.id },
            order: { sortOrder: 'DESC', createdAt: 'DESC' },
            take: need,
          });
          for (const u of us) {
            units.push({
              containerSize: cut.containerSize,
              containerNumber: u.containerNumber,
              sealNumber: u.sealNumber ?? null,
              vgmTons: Number(u.vgmTons),
              isHazardous: u.isHazardous,
              isReefer: u.isReefer,
            });
            need--;
          }
        }
      }
      const weightShare = round3(
        Number(booking.cargoTotalWeightVgm) * (wagons / totalWagons),
      );
      return {
        wagons,
        weightTons: weightShare,
        // Bookings without unit records fall back to the T2 LIFO trim.
        quantities: { bySize, ...(units.length === requested ? { units } : {}) },
      };
    }

    // BULK: the customer cancels wagons; tons follow the booking's own
    // tons-per-wagon ratio.
    const wagons = round2(Number(dto.wagons ?? 0));
    if (!wagons || wagons <= 0) {
      throw new BadRequestException('Specify how many wagons to cancel.');
    }
    if (wagons >= totalWagons) {
      throw new BadRequestException(
        'That would cancel the whole booking — use booking cancellation instead of a partial wagon cancel.',
      );
    }
    // ponytail: proportional sizing (tons/wagon = total/wagons). PER_ITEM item
    // rounding happens here too; switch to items_per_wagon_map sizing if bulk
    // PER_ITEM cancels ever need to be exact per item.
    let tons = Number(booking.cargoTotalWeightVgm) * (wagons / totalWagons);
    const isPerItem = booking.bulkTotalWeightTons != null;
    tons = isPerItem ? Math.floor(tons) : round3(tons);
    if (tons <= 0) {
      throw new BadRequestException('The requested cut is too small to release cargo.');
    }
    return { wagons, weightTons: tons, quantities: { bulkTons: tons } };
  }

  /**
   * Specific-wagon cancellation: the customer picked wagons in the Wagons tab.
   * Everything is derived from the selected allocations — container bookings
   * get their exact unit snapshots up front (T2 then cuts precisely these,
   * not a LIFO guess), bulk gets the wagons' actual allocated tonnage.
   */
  private async resolveCutFromAllocations(
    booking: Booking,
    allocationIds: string[],
    totalWagons: number,
  ): Promise<RequestedCut> {
    const allocations = await this.dataSource.getRepository(WagonBookingAllocation).find({
      where: { id: In(allocationIds), bookingId: booking.id },
      relations: { containerItems: true },
    });
    if (allocations.length !== allocationIds.length) {
      throw new BadRequestException(
        'Some selected wagons no longer belong to this booking — refresh and pick again.',
      );
    }
    const notCancellable = allocations.filter(
      (a) => a.status !== 'PLANNED' && a.status !== 'RESERVED',
    );
    if (notCancellable.length) {
      throw new BadRequestException(
        'A selected wagon is already loaded or departed and cannot be cancelled.',
      );
    }

    const wagons = allocations.length;
    if (wagons >= totalWagons) {
      throw new BadRequestException(
        'That would cancel the whole booking — use booking cancellation instead of a partial wagon cancel.',
      );
    }

    if (booking.freightType !== 'CONTAINER') {
      const allocated = allocations.reduce(
        (s, a) => s + Number(a.allocatedWeightTons || 0),
        0,
      );
      const tons =
        allocated > 0
          ? round3(allocated)
          : round3(Number(booking.cargoTotalWeightVgm) * (wagons / totalWagons));
      return {
        wagons,
        weightTons: tons,
        quantities: { bulkTons: tons, allocationIds },
      };
    }

    // Container: the selected wagons' items name the exact physical boxes.
    const numbers = allocations
      .flatMap((a) => a.containerItems ?? [])
      .map((i) => i.containerNumber)
      .filter((n): n is string => !!n);
    if (!numbers.length) {
      throw new BadRequestException(
        'The selected wagons carry no container records — cancel by quantity instead.',
      );
    }
    const lines = await this.dataSource.getRepository(BookingContainer).find({
      where: { bookingId: booking.id },
    });
    const unitRepo = this.dataSource.getRepository(BookingContainerUnit);
    const units: CancelledUnitSnapshot[] = [];
    const bySize: Record<string, number> = {};
    for (const line of lines) {
      const size = line.containerSize ?? '';
      const lineUnits = await unitRepo.find({ where: { bookingContainerId: line.id } });
      for (const u of lineUnits) {
        if (!numbers.includes(u.containerNumber)) continue;
        units.push({
          containerSize: size,
          containerNumber: u.containerNumber,
          sealNumber: u.sealNumber ?? null,
          vgmTons: Number(u.vgmTons),
          isHazardous: u.isHazardous,
          isReefer: u.isReefer,
        });
        bySize[size] = (bySize[size] ?? 0) + 1;
      }
    }
    if (units.length !== numbers.length) {
      throw new BadRequestException(
        'Wagon container records are out of sync with the booking — contact EDR support.',
      );
    }
    return {
      wagons,
      weightTons: round3(units.reduce((s, u) => s + Number(u.vgmTons || 0), 0)),
      quantities: { bySize, units, allocationIds },
    };
  }

  /** Credit = the cancelled share of the ORIGINAL price (old-price rebooking). */
  private creditFor(booking: Booking, wagons: number): number {
    const totalWagons = Number(booking.wagonsRequired ?? 0);
    if (totalWagons <= 0) return 0;
    return round2(Number(booking.totalAmount) * (wagons / totalWagons));
  }

  private async feeRate(): Promise<Rate> {
    const rate = await this.dataSource.getRepository(Rate).findOne({
      where: {
        rateType: WAGON_CANCELLATION_FEE_RATE_TYPE,
        rateUnit: 'PER_WAGON',
        status: 'LIVE',
      },
      order: { createdAt: 'DESC' },
    });
    if (!rate) {
      throw new BadRequestException(
        'No LIVE per-wagon CANCELLATION_FEE rate is configured — ask EDR to set it in the rate engine (unit PER_WAGON).',
      );
    }
    return rate;
  }

  /**
   * Trim `bySize` units off the booking's container lines, newest line first,
   * LIFO within a line — the exact applySplit mechanics. Returns snapshots of
   * every physical unit soft-deleted, for later reconstruction.
   */
  private async reduceContainerLines(
    manager: EntityManager,
    booking: Booking,
    bySize: Record<string, number>,
  ): Promise<CancelledUnitSnapshot[]> {
    const snapshots: CancelledUnitSnapshot[] = [];
    for (const [size, toDrop] of Object.entries(bySize)) {
      let remaining = toDrop;
      const lines = await manager.getRepository(BookingContainer).find({
        where: { bookingId: booking.id, containerSize: size },
        order: { createdAt: 'DESC' },
      });
      const live = lines.reduce((s, l) => s + Number(l.quantity ?? 0), 0);
      if (live < toDrop) {
        throw new BadRequestException(
          `Booking changed since the request: only ${live} × ${size}ft left, cannot cancel ${toDrop}.`,
        );
      }
      for (const line of lines) {
        if (remaining <= 0) break;
        const qty = Number(line.quantity ?? 0);
        const drop = Math.min(remaining, qty);
        remaining -= drop;

        const units = await manager.getRepository(BookingContainerUnit).find({
          where: { bookingContainerId: line.id },
          order: { sortOrder: 'DESC', createdAt: 'DESC' },
          take: drop,
        });
        for (const u of units) {
          snapshots.push({
            containerSize: size,
            containerNumber: u.containerNumber,
            sealNumber: u.sealNumber ?? null,
            vgmTons: Number(u.vgmTons),
            isHazardous: u.isHazardous,
            isReefer: u.isReefer,
          });
        }
        if (units.length < drop) {
          throw new BadRequestException(
            `Booking line ${line.id} has ${units.length} physical unit record(s) but ${drop} must be cancelled — units out of sync.`,
          );
        }
        const droppedVgm = round3(units.reduce((s, u) => s + Number(u.vgmTons || 0), 0));

        if (drop === qty) {
          await manager.getRepository(BookingContainer).softDelete(line.id);
          await manager
            .getRepository(BookingContainerUnit)
            .softDelete(units.map((u) => u.id));
          continue;
        }
        await manager.getRepository(BookingContainerUnit).softDelete(units.map((u) => u.id));
        const keptUnits = await manager.getRepository(BookingContainerUnit).find({
          where: { bookingContainerId: line.id },
        });
        await manager.getRepository(BookingContainer).update(line.id, {
          quantity: qty - drop,
          wagonsRequired: round2((qty - drop) * wagonsPerUnitForSize(Number(size))),
          totalVgmTons: round3(Number(line.totalVgmTons) - droppedVgm),
          hazardousQuantity: keptUnits.filter((u) => u.isHazardous).length,
          reeferQuantity: keptUnits.filter((u) => u.isReefer).length,
        });
      }
    }
    return snapshots;
  }

  /**
   * Release the cancelled wagons from the schedule at REQUEST time. Returns
   * true when something was actually released (booking was on a train) — the
   * caller then stamps `releasedAtRequest` so T2 skips its release step.
   */
  private async releaseAtRequest(bookingId: string, cut: RequestedCut): Promise<boolean> {
    const had = await this.dataSource.getRepository(WagonBookingAllocation).count({
      where: { bookingId },
    });
    if (had === 0) return false;

    await this.dataSource.transaction(async (manager) => {
      if (cut.quantities.units?.length) {
        await this.releaseContainerAllocations(
          manager,
          bookingId,
          cut.quantities.units.map((u) => u.containerNumber),
        );
      } else if (!cut.quantities.bySize) {
        await this.releaseBulkAllocations(
          manager,
          bookingId,
          cut.wagons,
          cut.quantities.allocationIds,
        );
      }
      // Container booking without unit records: nothing to match on — the
      // wagons release at T2 via the LIFO trim instead.
    });

    const left = await this.dataSource.getRepository(WagonBookingAllocation).count({
      where: { bookingId },
    });
    return left < had;
  }

  /**
   * Cut EXACTLY the snapshotted units (specific-wagon cancellation): soft-delete
   * them and rebalance each affected line. Returns the snapshots of the units
   * actually cut, so drift since the request fails loudly instead of guessing.
   */
  private async reduceContainerUnitsExact(
    manager: EntityManager,
    booking: Booking,
    wanted: CancelledUnitSnapshot[],
  ): Promise<CancelledUnitSnapshot[]> {
    const numbers = wanted.map((u) => u.containerNumber);
    const lines = await manager.getRepository(BookingContainer).find({
      where: { bookingId: booking.id },
    });
    const cut: CancelledUnitSnapshot[] = [];
    for (const line of lines) {
      const size = line.containerSize ?? '';
      const lineUnits = await manager.getRepository(BookingContainerUnit).find({
        where: { bookingContainerId: line.id },
      });
      const doomed = lineUnits.filter((u) => numbers.includes(u.containerNumber));
      if (!doomed.length) continue;

      await manager.getRepository(BookingContainerUnit).softDelete(doomed.map((u) => u.id));
      for (const u of doomed) {
        cut.push({
          containerSize: size,
          containerNumber: u.containerNumber,
          sealNumber: u.sealNumber ?? null,
          vgmTons: Number(u.vgmTons),
          isHazardous: u.isHazardous,
          isReefer: u.isReefer,
        });
      }
      const kept = lineUnits.filter((u) => !numbers.includes(u.containerNumber));
      if (!kept.length) {
        await manager.getRepository(BookingContainer).softDelete(line.id);
        continue;
      }
      const doomedVgm = round3(doomed.reduce((s, u) => s + Number(u.vgmTons || 0), 0));
      await manager.getRepository(BookingContainer).update(line.id, {
        quantity: kept.length,
        wagonsRequired: round2(kept.length * wagonsPerUnitForSize(Number(size))),
        totalVgmTons: round3(Number(line.totalVgmTons) - doomedVgm),
        hazardousQuantity: kept.filter((u) => u.isHazardous).length,
        reeferQuantity: kept.filter((u) => u.isReefer).length,
      });
    }
    if (cut.length !== wanted.length) {
      throw new BadRequestException(
        `Booking changed since the request: ${cut.length}/${wanted.length} selected container(s) still on it.`,
      );
    }
    return cut;
  }

  private async reduceBulk(
    manager: EntityManager,
    booking: Booking,
    tons: number,
  ): Promise<void> {
    if (tons >= Number(booking.cargoTotalWeightVgm)) {
      throw new BadRequestException(
        'Booking changed since the request: the cut no longer leaves any cargo.',
      );
    }
    if (booking.bulkTotalWeightTons != null) {
      const share = tons / Number(booking.cargoTotalWeightVgm);
      await manager.getRepository(Booking).update(booking.id, {
        bulkTotalWeightTons: round3(Number(booking.bulkTotalWeightTons) * (1 - share)),
      });
    }
  }

  /**
   * Free the wagon capacity of the cancelled container units. Items are matched
   * by container number; an allocation left with no items is deleted whole
   * (hard delete — the unassignBooking convention for allocation rows).
   * A booking not yet placed on a train simply has nothing to release.
   */
  private async releaseContainerAllocations(
    manager: EntityManager,
    bookingId: string,
    containerNumbers: string[],
  ): Promise<void> {
    if (!containerNumbers.length) return;
    const allocations = await manager.getRepository(WagonBookingAllocation).find({
      where: { bookingId },
      relations: { containerItems: true },
    });
    for (const alloc of allocations) {
      const items = alloc.containerItems ?? [];
      const cut = items.filter(
        (i) => i.containerNumber && containerNumbers.includes(i.containerNumber),
      );
      if (!cut.length) continue;
      await manager
        .getRepository(WagonAllocationContainerItem)
        .delete(cut.map((i) => i.id));
      if (cut.length === items.length) {
        await manager.getRepository(WagonBookingAllocation).delete(alloc.id);
      } else {
        const cutWeight = cut.reduce((s, i) => s + Number(i.grossWeightTons ?? 0), 0);
        await manager.getRepository(WagonBookingAllocation).update(alloc.id, {
          allocatedWeightTons: round3(Number(alloc.allocatedWeightTons) - cutWeight),
        });
      }
    }
  }

  /**
   * Free whole bulk wagons — the customer-picked allocations when given
   * (specific-wagon cancel), topping up newest-first for any picked id that no
   * longer exists (re-batch between request and fee payment).
   */
  private async releaseBulkAllocations(
    manager: EntityManager,
    bookingId: string,
    wagons: number,
    pickedIds?: string[],
  ): Promise<void> {
    const toFree = Math.round(wagons);
    if (toFree <= 0) return;
    let allocations: WagonBookingAllocation[] = [];
    if (pickedIds?.length) {
      allocations = await manager.getRepository(WagonBookingAllocation).find({
        where: { id: In(pickedIds), bookingId },
      });
    }
    if (allocations.length < toFree) {
      const have = new Set(allocations.map((a) => a.id));
      const fill = await manager.getRepository(WagonBookingAllocation).find({
        where: { bookingId },
        order: { createdAt: 'DESC' },
      });
      for (const a of fill) {
        if (allocations.length >= toFree) break;
        if (!have.has(a.id)) allocations.push(a);
      }
    }
    allocations = allocations.slice(0, toFree);
    if (!allocations.length) return;
    const ids = allocations.map((a) => a.id);
    await manager
      .getRepository(WagonAllocationBulkLoad)
      .delete({ wagonBookingAllocationId: In(ids) });
    await manager.getRepository(WagonBookingAllocation).delete(ids);
  }

  /** Pre-reduction quantities snapshot (only when the booking was never split before). */
  private async currentQuantities(
    manager: EntityManager,
    booking: Booking,
    _droppedWeight: number,
  ): Promise<{ bulkTons?: number; bySize?: Record<string, number> }> {
    if (booking.freightType !== 'CONTAINER') {
      return { bulkTons: Number(booking.cargoTotalWeightVgm) };
    }
    // Lines were already reduced inside this transaction — read them with
    // deleted rows included to reconstruct the pre-cut ledger.
    const lines = await manager.getRepository(BookingContainer).find({
      where: { bookingId: booking.id },
      withDeleted: true,
    });
    const bySize: Record<string, number> = {};
    for (const line of lines) {
      const size = line.containerSize ?? '';
      bySize[size] = (bySize[size] ?? 0) + Number(line.quantity ?? 0);
    }
    return { bySize };
  }

  /** The create-DTO that reconstructs the cancelled cargo on the chosen day. */
  private buildRebookDto(
    row: BookingWagonCancellation,
    scheduledDate: string,
  ): CreateBookingUnderContractDto {
    const dto: CreateBookingUnderContractDto = { scheduledDate };
    const q = row.cancelledQuantities;

    if (q.bySize && Object.keys(q.bySize).length) {
      const units = q.units ?? [];
      dto.containers = Object.entries(q.bySize).map(([size, quantity]) => {
        const sized = units.filter((u) => u.containerSize === size);
        if (sized.length !== quantity) {
          throw new BadRequestException(
            `Credit is missing unit snapshots for size ${size} (${sized.length}/${quantity}) — contact EDR support.`,
          );
        }
        return {
          containerSize: size,
          quantity,
          units: sized.map((u) => ({
            containerNumber: u.containerNumber,
            sealNumber: u.sealNumber ?? undefined,
            vgmTons: u.vgmTons,
            isHazardous: u.isHazardous,
            isReefer: u.isReefer,
          })),
          hazardousQuantity: sized.filter((u) => u.isHazardous).length,
          reeferQuantity: sized.filter((u) => u.isReefer).length,
        };
      });
      return dto;
    }

    dto.bulkLines = [{ cargoWeightTons: Number(q.bulkTons ?? row.weightTons) }];
    return dto;
  }

  /**
   * Carry the source booking's finished clearance onto the rebooked one: the
   * cargo is already cleared; a new train date needs no new customs cycle.
   * Seeds the standard milestone set idempotently, then mirrors every
   * non-pending milestone status from the source by milestone code.
   */
  private async copyClearanceState(source: Booking, newBookingId: string): Promise<void> {
    const repo = this.dataSource.getRepository(ClearanceMilestone);
    const sourceMilestones = await repo.find({ where: { bookingId: source.id } });
    if (!sourceMilestones.length) return;

    try {
      await this.clearanceMilestones.ensureBookingMilestones(
        newBookingId,
        source.tradeDirection,
      );
      const targets = await repo.find({ where: { bookingId: newBookingId } });
      const byCode = new Map(targets.map((m) => [m.milestoneCode, m]));
      for (const src of sourceMilestones) {
        if (src.status === 'PENDING') continue;
        const target = byCode.get(src.milestoneCode);
        if (!target) continue;
        await repo.update(target.id, {
          status: src.status,
          triggeredAt: src.triggeredAt,
          triggeredByUserId: src.triggeredByUserId,
          triggeredByDoc: src.triggeredByDoc,
          note: src.note,
          metadata: src.metadata,
        });
      }
      if (source.clearanceCurrentPhase) {
        await this.dataSource.getRepository(Booking).update(newBookingId, {
          clearanceCurrentPhase: source.clearanceCurrentPhase,
          preClearanceFinalizedAt: source.preClearanceFinalizedAt,
          dutyRequired: source.dutyRequired,
        });
      }
    } catch (err) {
      // Clearance copy must never lose a paid rebooking — staff can re-complete
      // milestones by hand if this ever fails.
      this.logger.error(
        `Clearance copy ${source.id} → ${newBookingId} failed: ${err instanceof Error ? err.message : String(err)}`,
      );
    }
  }

  private notifyCustomer(booking: Booking, title: string, body: string, linkBookingId?: string): void {
    void this.inbox.notify({
      recipients: { companyId: booking.companyId },
      audience: NotificationAudience.PORTAL,
      type: NotificationType.BOOKING_STATUS,
      title,
      body,
      link: `/bookings/${linkBookingId ?? booking.id}`,
      data: { bookingId: linkBookingId ?? booking.id, reference: booking.reference },
    });
  }

  private notifyStaff(booking: Booking, title: string, body: string): void {
    void this.inbox.notify({
      recipients: { allBackoffice: true },
      audience: NotificationAudience.BACKOFFICE,
      type: NotificationType.BOOKING_STATUS,
      title,
      body,
      link: `/bookings/${booking.id}`,
      data: { bookingId: booking.id, reference: booking.reference },
    });
  }
}