import { Injectable, Logger, UnprocessableEntityException } from '@nestjs/common';
import { OnEvent } from '@nestjs/event-emitter';
import { Freight } from '@edr/types';

import { BillingService, InvoiceEventPayload } from '../billing/billing.service';
import { Invoice } from '../billing/entities/invoice.entity';
import { BookingsRepository } from '../bookings/bookings.repository';
import { Booking } from '../bookings/entities/booking.entity';
import { ContractPricingBreakdown } from './contract-pricing.service';
import { ContractNotifierService } from './contract-notifier.service';
import { ContractsRepository } from './contracts.repository';
import { Contract } from './entities/contract.entity';

/** Invoice `type` for the contract-level fee (Path B ONE_TIME, after counter-sign). */
export const CLEARANCE_CONTRACT_INVOICE_TYPE = 'CLEARANCE_CONTRACT';
/** Invoice `type` for the per-shipment fee (Path B GENERAL, at shipment request). */
export const CLEARANCE_BOOKING_INVOICE_TYPE = 'CLEARANCE_BOOKING';

/**
 * The prepaid customs clearance service fee (Path B) — the GL service charge,
 * separate from both freight (booking invoice) and duty/tax (paid offline).
 * Issued as its own `clearance`-source invoice and paid BEFORE the clearance
 * document step opens and before GL touches the file:
 *  - ONE_TIME: once per contract, at staff counter-sign
 *    (AWAITING_CLEARANCE_PAYMENT → paid → AWAITING_CLEARANCE_DOCUMENTS);
 *  - GENERAL: once per shipment request, on the initiated booking instance
 *    (booking AWAITING_CLEARANCE_PAYMENT → paid → AWAITING_DOCUMENTS).
 * The fee amount is the frozen CUSTOMS_CLEARANCE contract rate snapshot, so
 * customers pay what their contract shows, not the live rate of the day.
 */
@Injectable()
export class ClearanceFeeService {
  private readonly logger = new Logger(ClearanceFeeService.name);

  constructor(
    private readonly billing: BillingService,
    private readonly contractsRepository: ContractsRepository,
    private readonly bookingsRepository: BookingsRepository,
    private readonly notifier: ContractNotifierService,
  ) {}

  /** The frozen flat fee for a contract; falls back to the pricing breakdown. */
  private async feeAmountOrNull(
    contract: Contract,
  ): Promise<{ amount: number; currency: string } | null> {
    const snapshots = await this.contractsRepository.findRateSnapshots(contract.id);
    const snapshot = snapshots.find(
      (s) => s.isClearance || s.rateCode === 'CUSTOMS_CLEARANCE',
    );
    if (snapshot && Number(snapshot.unitPrice) > 0) {
      return { amount: Number(snapshot.unitPrice), currency: snapshot.currency };
    }
    const breakdown = contract.pricingBreakdown as ContractPricingBreakdown | null;
    const line = breakdown?.lineItems?.find((l) => l.code === 'CUSTOMS_CLEARANCE');
    if (line && Number(line.unitPrice) > 0) {
      return { amount: Number(line.unitPrice), currency: breakdown!.currency };
    }
    return null;
  }

  private async feeAmount(
    contract: Contract,
  ): Promise<{ amount: number; currency: string }> {
    const fee = await this.feeAmountOrNull(contract);
    if (!fee) {
      throw new UnprocessableEntityException(
        `Contract ${contract.reference} has no frozen customs clearance fee — regenerate its price with a live CUSTOMS_CLEARANCE rate.`,
      );
    }
    return fee;
  }

  /**
   * Whether the payment gate applies. Skipped for government/unlinked
   * contracts (no company to bill — invoices require one, same rule the
   * booking invoice applies) and for legacy customs contracts frozen before
   * the fee existed (no CUSTOMS_CLEARANCE snapshot to bill from) — both keep
   * the pre-fee flow instead of dead-ending.
   */
  async gateApplies(contract: Contract): Promise<boolean> {
    if (!contract.customsClearingEnabled || !contract.companyId) return false;
    if ((await this.feeAmountOrNull(contract)) !== null) return true;
    this.logger.warn(
      `Contract ${contract.reference} has customs enabled but no frozen clearance fee — skipping the prepay gate (legacy contract).`,
    );
    return false;
  }

  /** Issue (idempotently) the ONE_TIME contract-level fee invoice. */
  async issueForContract(contract: Contract): Promise<Invoice> {
    const existing = await this.billing.findPayable(
      Freight.InvoiceSource.Clearance,
      contract.id,
      CLEARANCE_CONTRACT_INVOICE_TYPE,
    );
    if (existing) return existing;

    const { amount, currency } = await this.feeAmount(contract);
    const invoice = await this.billing.generateInvoice({
      source: Freight.InvoiceSource.Clearance,
      sourceId: contract.id,
      type: CLEARANCE_CONTRACT_INVOICE_TYPE,
      companyId: contract.companyId!,
      companyProfileId: contract.companyProfileId!,
      currency,
      lines: [
        {
          chargeType: 'CUSTOMS_CLEARANCE',
          description: `Customs clearance service fee — contract ${contract.reference}`,
          quantity: 1,
          unitRate: amount,
          amount,
          currency,
        },
      ],
      status: Freight.InvoiceStatus.Pending,
    });
    this.notifier.clearanceFeeDue(contract, amount, currency);
    return invoice;
  }

  /** Issue (idempotently) the GENERAL per-shipment fee invoice on the booking. */
  async issueForBooking(booking: Booking, contract: Contract): Promise<Invoice> {
    const existing = await this.billing.findPayable(
      Freight.InvoiceSource.Clearance,
      booking.id,
      CLEARANCE_BOOKING_INVOICE_TYPE,
    );
    if (existing) return existing;

    const { amount, currency } = await this.feeAmount(contract);
    const invoice = await this.billing.generateInvoice({
      source: Freight.InvoiceSource.Clearance,
      sourceId: booking.id,
      type: CLEARANCE_BOOKING_INVOICE_TYPE,
      companyId: booking.companyId ?? contract.companyId!,
      companyProfileId: booking.companyProfileId ?? contract.companyProfileId!,
      currency,
      lines: [
        {
          chargeType: 'CUSTOMS_CLEARANCE',
          description: `Customs clearance service fee — shipment ${booking.reference}`,
          quantity: 1,
          unitRate: amount,
          amount,
          currency,
        },
      ],
      status: Freight.InvoiceStatus.Pending,
    });
    this.notifier.clearanceFeeDue(contract, amount, currency, booking.reference);
    return invoice;
  }

  /**
   * Settlement branch point for `clearance`-source invoices: unlock the
   * document-upload step the fee was gating. Idempotent — a replayed event on
   * an already-advanced contract/booking is a no-op.
   */
  @OnEvent('clearance.invoice.paid')
  async onClearanceInvoicePaid(payload: InvoiceEventPayload): Promise<void> {
    this.logger.log(
      `clearance.invoice.paid (${payload.type}) for ${payload.sourceId} from ${payload.invoiceId}`,
    );
    switch (payload.type) {
      case CLEARANCE_CONTRACT_INVOICE_TYPE:
        await this.advanceContract(payload.sourceId);
        break;
      case CLEARANCE_BOOKING_INVOICE_TYPE:
        await this.advanceBooking(payload.sourceId);
        break;
      default:
        this.logger.warn(
          `Unhandled clearance invoice type "${payload.type}" paid (${payload.invoiceId})`,
        );
    }
  }

  private async advanceContract(contractId: string): Promise<void> {
    const contract = await this.contractsRepository.findById(contractId);
    if (!contract) {
      this.logger.warn(`Cannot advance unknown contract ${contractId} on clearance fee payment.`);
      return;
    }
    if (contract.status !== 'AWAITING_CLEARANCE_PAYMENT') return;

    await this.contractsRepository.update(contractId, {
      status: 'AWAITING_CLEARANCE_DOCUMENTS',
      clearanceStatus: 'AWAITING_DOCUMENTS',
      clearanceFeePaidAt: new Date(),
    } as never);
    const updated = await this.contractsRepository.findByIdWithRelations(contractId);
    if (updated) this.notifier.clearanceFeePaid(updated);
  }

  private async advanceBooking(bookingId: string): Promise<void> {
    const booking = await this.bookingsRepository.findById(bookingId);
    if (!booking) {
      this.logger.warn(`Cannot advance unknown booking ${bookingId} on clearance fee payment.`);
      return;
    }
    if (booking.status !== 'AWAITING_CLEARANCE_PAYMENT') return;

    await this.bookingsRepository.update(bookingId, {
      status: 'AWAITING_DOCUMENTS',
      clearanceFeePaidAt: new Date(),
    } as never);
    if (booking.contractId) {
      const contract = await this.contractsRepository.findByIdWithRelations(
        booking.contractId,
      );
      if (contract) this.notifier.clearanceFeePaid(contract, booking.reference);
    }
  }
}