import { BadRequestException, ConflictException, Injectable, Logger, NotFoundException } from "@nestjs/common";
import { InjectDataSource } from "@nestjs/typeorm";
import { DataSource, EntityManager } from "typeorm";

import { Invoice } from "../billing/entities/invoice.entity";
import { NotificationsService } from "../notifications/notifications.service";
import { sendCompanyChannels } from "../notifications/notify-company.util";
import { EimsClientService } from "./eims-client.service";
import {
  EimsBulkCancelItemResult,
  EimsBulkCancelRequest,
  EimsBulkCancelResponse,
  EimsCancelRequest,
  EimsCancelResponse,
  EimsInvoiceStatus,
  EimsInvoiceStatusView,
} from "./eims-registration.types";
import { toEimsInvoiceStatusView } from "./eims-invoice-view.util";

/**
 * `POST /v1/cancel` for one already-registered invoice.
 *
 * Simpler than registration: cancellation carries no `InvoiceCounter`/`DocumentNumber`, so none of
 * `EimsSystemState`'s reservation machinery applies, and — unlike registration — a retried cancel
 * is safe: the collection's bulk-cancel example shows MoR itself rejects a second cancel with
 * "IRN already Canceled.", so there is no double-filing risk the way an unacknowledged register
 * call has. That is what makes the simpler shape below correct: no system-wide block, no in-flight
 * marker, just a lock-check-unlock before the call and a fresh lock-check-write after it.
 *
 * ponytail: the eligibility check (TX1) and the write (TX2) are not one atomic operation, so two
 * concurrent cancels on the same invoice could both pass TX1 and both call MoR — wasted, but safe,
 * per the paragraph above. Upgrade to a single locked reservation (like registration's) only if
 * MoR's cancel endpoint turns out not to be idempotent after all.
 *
 * Bearer-authenticated but unsigned (`postBearer`), same as `/v1/verify` — the collection's saved
 * `/v1/cancel` request carries no `{request,signature,certificate}` envelope.
 */
@Injectable()
export class EimsCancellationService {
  private readonly logger = new Logger(EimsCancellationService.name);

  constructor(
    @InjectDataSource() private readonly dataSource: DataSource,
    private readonly client: EimsClientService,
    private readonly notifications: NotificationsService,
  ) {}

  /**
   * Refuses an already-cancelled invoice with a 409, rather than a silent no-op — IRC-N010 in
   * MoR's Master Compliance Checklist requires "an appropriate error or rejection message" for a
   * repeat cancellation, not a quiet success. No HTTP call either way: this is a local check, not
   * a retry against MoR. Also refuses an invoice that was never registered — there is no IRN to
   * cancel.
   */
  async cancelInvoiceWithEims(
    invoiceId: string,
    reasonCode: string,
    remark?: string,
  ): Promise<EimsInvoiceStatusView> {
    const eligible = await this.dataSource.transaction(async (manager) => {
      const invoice = await this.lockInvoice(manager, invoiceId);
      if (invoice.eimsStatus === EimsInvoiceStatus.Cancelled) {
        throw new ConflictException({
          code: "EIMS_ALREADY_CANCELLED",
          message: `Invoice ${invoice.invoiceNumber} was already cancelled with EIMS${invoice.eimsCancellationDate ? ` (${invoice.eimsCancellationDate})` : ""}.`,
        });
      }
      if (!invoice.eimsIrn) {
        throw new BadRequestException({
          code: "EIMS_NOT_REGISTERED",
          message: `Invoice ${invoice.invoiceNumber} was never registered with EIMS — nothing to cancel.`,
        });
      }
      return invoice;
    });

    const request: EimsCancelRequest = { Irn: eligible.eimsIrn!, ReasonCode: reasonCode, Remark: remark ?? "" };
    // Outside any transaction — no DB lock is held across the wire.
    const response = await this.client.postBearer<EimsCancelRequest, EimsCancelResponse>(
      "/v1/cancel",
      request,
    );
    const cancellationDate = response?.body?.cancellationDate ?? null;

    await this.dataSource.transaction(async (manager) => {
      const invoice = await this.lockInvoice(manager, invoiceId);
      // Re-checked under lock: a concurrent call may have already recorded this cancellation.
      if (invoice.eimsStatus === EimsInvoiceStatus.Cancelled) return;
      await manager.update(Invoice, invoiceId, {
        eimsStatus: EimsInvoiceStatus.Cancelled,
        eimsCancelledAt: new Date(),
        eimsCancellationDate: cancellationDate,
        eimsCancellationReasonCode: reasonCode,
        eimsCancellationRemark: remark ?? null,
      });
    });
    this.logger.log(`Invoice ${eligible.invoiceNumber} cancelled with EIMS (IRN ${eligible.eimsIrn})`);

    await this.notifyBuyer(eligible);
    return this.getEimsCancellationStatus(invoiceId);
  }

  /**
   * `POST /v1/bulkCancel` — one MoR call for every eligible invoice in `items`, matching the
   * collection's own shape (an array in, an array of mixed success/error results back).
   *
   * Same local-eligibility doctrine as `cancelInvoiceWithEims`, applied per item before anything
   * goes to MoR: an already-cancelled or never-registered invoice is refused right here (no HTTP
   * call, no seat in the batch) rather than sent and rejected remotely. Only genuinely eligible
   * invoices are batched into the one `/v1/bulkCancel` request; everything else is reported back
   * immediately.
   *
   * ponytail: the eligibility pass is per-invoice transactions, not one covering the whole batch —
   * same reasoning as the single-cancel path (cancel is idempotent at MoR, so a lock held across
   * every item for the whole call isn't needed for correctness, only for avoiding a wasted call on
   * an item that's already ineligible).
   */
  async cancelBulkWithEims(
    items: Array<{ invoiceId: string; reasonCode: string; remark?: string }>,
  ): Promise<EimsBulkCancelItemResult[]> {
    const results = new Map<string, EimsBulkCancelItemResult>();
    const eligible: Array<{ invoice: Invoice; reasonCode: string; remark?: string }> = [];

    for (const item of items) {
      try {
        const invoice = await this.dataSource.transaction(async (manager) => {
          const inv = await this.lockInvoice(manager, item.invoiceId);
          if (inv.eimsStatus === EimsInvoiceStatus.Cancelled) {
            throw new ConflictException(
              `Invoice ${inv.invoiceNumber} was already cancelled with EIMS${inv.eimsCancellationDate ? ` (${inv.eimsCancellationDate})` : ""}.`,
            );
          }
          if (!inv.eimsIrn) {
            throw new BadRequestException(
              `Invoice ${inv.invoiceNumber} was never registered with EIMS — nothing to cancel.`,
            );
          }
          return inv;
        });
        eligible.push({ invoice, reasonCode: item.reasonCode, remark: item.remark });
      } catch (err) {
        results.set(item.invoiceId, {
          invoiceId: item.invoiceId,
          success: false,
          message: (err as Error).message,
        });
      }
    }

    if (eligible.length > 0) {
      const request: EimsBulkCancelRequest = eligible.map((e) => ({
        Irn: e.invoice.eimsIrn!,
        ReasonCode: e.reasonCode,
        Remark: e.remark ?? "",
      }));
      // Outside any transaction — no DB lock held across the wire, same as single cancel.
      const response = await this.client.postBearer<EimsBulkCancelRequest, EimsBulkCancelResponse>(
        "/v1/bulkCancel",
        request,
      );
      const byIrn = new Map((response?.body ?? []).map((entry) => [entry.Irn, entry]));

      for (const { invoice, reasonCode, remark } of eligible) {
        const entry = byIrn.get(invoice.eimsIrn!);
        const failed = !entry || "Status" in entry;
        if (failed) {
          const message = entry && "msg" in entry ? entry.msg : "EIMS bulk cancel returned no result for this invoice.";
          this.logger.warn(`Invoice ${invoice.invoiceNumber} bulk cancel failed: ${message}`);
          results.set(invoice.id, { invoiceId: invoice.id, success: false, message });
          continue;
        }

        await this.dataSource.transaction(async (manager) => {
          const fresh = await this.lockInvoice(manager, invoice.id);
          // Re-checked under lock: a concurrent call may have already recorded this cancellation.
          if (fresh.eimsStatus === EimsInvoiceStatus.Cancelled) return;
          await manager.update(Invoice, invoice.id, {
            eimsStatus: EimsInvoiceStatus.Cancelled,
            eimsCancelledAt: new Date(),
            // The bulk success shape carries no cancellationDate at all, unlike single cancel.
            eimsCancellationDate: null,
            eimsCancellationReasonCode: reasonCode,
            eimsCancellationRemark: remark ?? null,
          });
        });
        this.logger.log(`Invoice ${invoice.invoiceNumber} cancelled with EIMS via bulk (IRN ${invoice.eimsIrn})`);
        await this.notifyBuyer(invoice);
        results.set(invoice.id, {
          invoiceId: invoice.id,
          success: true,
          message: `Invoice ${invoice.invoiceNumber} cancelled with EIMS.`,
        });
      }
    }

    return items.map((item) => results.get(item.invoiceId)!);
  }

  async getEimsCancellationStatus(invoiceId: string): Promise<EimsInvoiceStatusView> {
    const invoice = await this.dataSource.manager.findOne(Invoice, { where: { id: invoiceId } });
    if (!invoice) throw new NotFoundException(`Invoice ${invoiceId} not found`);
    return toEimsInvoiceStatusView(invoice);
  }

  /** Best-effort — a notification failure must never mask a cancellation that already succeeded. */
  private async notifyBuyer(invoice: Invoice): Promise<void> {
    if (!invoice.companyId) return;
    try {
      await sendCompanyChannels(
        this.dataSource,
        this.notifications,
        invoice.companyId,
        `Invoice ${invoice.invoiceNumber} has been cancelled with MoR EIMS.`,
      );
    } catch (err) {
      this.logger.warn(`EIMS buyer notification failed for invoice ${invoice.id}: ${(err as Error).message}`);
    }
  }

  private async lockInvoice(manager: EntityManager, invoiceId: string): Promise<Invoice> {
    const invoice = await manager
      .createQueryBuilder(Invoice, "invoice")
      .setLock("pessimistic_write")
      .where("invoice.id = :invoiceId", { invoiceId })
      .getOne();
    if (!invoice) throw new NotFoundException(`Invoice ${invoiceId} not found`);
    return invoice;
  }
}