import { Injectable, Logger, OnModuleInit } from "@nestjs/common";
import { ConfigService } from "@nestjs/config";

import { EimsConfig } from "../../config/eims.config";
import { ETradeService } from "../companies/services/etrade.service";
import { tryResolveMorGeo } from "../../config/mor-location.resolver";
import { EimsSellerDetails } from "../billing/eims-invoice.mapper";
import { buildEimsSeller } from "./eims-invoice-context";

const has = (value: string | null | undefined): value is string => Boolean(value && value.trim());

/**
 * EDR's own EIMS seller identity (LegalName/Phone/Region/Wereda/City), enriched from the same
 * e-Trade business-registry lookup already used for every customer company at onboarding — instead
 * of the whole thing being hand-maintained `EIMS_SELLER_*` config.
 *
 * **Static config is the source of truth, e-Trade is bootstrap/enrichment only.** MoR validates
 * `SellerDetails` against its own taxpayer registry (rule 7017, already cleared and live-tested
 * with the current static values) — e-Trade filling a gap is fine, e-Trade silently overriding a
 * value already confirmed against MoR is not. `getSellerDetails` therefore only reaches for the
 * e-Trade-derived value when the static one is blank; a static value, once set, is never replaced.
 * This also means the durable fallback is the static config, not this cache — the in-memory
 * snapshot disappearing on a process restart is harmless, not a reliability gap: every field it
 * could supply already has a working static value today, so filing is unaffected either way.
 *
 * `VatNumber` and `Email` are never sourced here — confirmed by reading e-Trade's actual response
 * shapes (`ETradeCompanyInfo`, `ETradeBusinessInfo`, `CompanyRegistrationData`): neither field
 * exists anywhere in what e-Trade returns. They stay on static config permanently, same as
 * `SubCity`/`Locality`/`HouseNumber`, which this pass doesn't touch.
 *
 * Cache shape follows `PositionTypePermissionsCache`'s precedent (`src/common/
 * position-type-permissions.cache.ts`) for "external/slow data, not fetched per request": a plain
 * field refreshed on a raw `setInterval`, `unref()`'d so it never holds the process open, and a
 * refresh failure keeps serving the previous snapshot rather than clearing it. Two deliberate
 * deviations from that precedent, both because `ETradeService` has no request timeout configured
 * at all (confirmed by reading it) and is a third-party dependency, unlike the DB:
 *  - the first fetch is fire-and-forget in `onModuleInit`, never awaited by boot;
 *  - `refresh()` is wrapped in a local timeout, and a second call while one is already in flight
 *    returns the same in-flight promise instead of starting a duplicate request.
 *
 * `getSellerDetails` is fully synchronous — zero I/O at call time — so a live invoice registration
 * never depends on e-Trade being reachable at that moment, whether or not it ever has been.
 */
@Injectable()
export class EimsSellerCacheService implements OnModuleInit {
  private readonly logger = new Logger(EimsSellerCacheService.name);

  /** Only the e-Trade-derived fields, used solely to fill a blank static value. */
  private cached: Partial<EimsSellerDetails> | null = null;
  /** Concurrency guard — a second `refresh()` call while one is running joins it. */
  private refreshing: Promise<void> | null = null;

  // ponytail: daily refresh, no invalidation hook — a change at e-Trade takes up to 24h to reach a
  // filed invoice. Wire a manual refresh() call (e.g. from an admin action) if that lag ever
  // matters; EDR's own business registration changes rarely enough that this is a generous
  // ceiling, not a real one.
  private static readonly REFRESH_INTERVAL_MS = 24 * 60 * 60 * 1000;
  /** Bounded locally since `ETradeService` itself sets none — see the class comment. */
  private static readonly REFRESH_TIMEOUT_MS = 10_000;

  constructor(
    private readonly etrade: ETradeService,
    private readonly config: ConfigService,
  ) {}

  onModuleInit(): void {
    void this.refresh();
    const timer = setInterval(() => void this.refresh(), EimsSellerCacheService.REFRESH_INTERVAL_MS);
    timer.unref?.();
  }

  /**
   * Static config wins whenever it's non-blank — that's the value already confirmed against MoR.
   * e-Trade fills a field only when the static one is empty. Synchronous, no I/O: safe to call on
   * every registration.
   */
  getSellerDetails(cfg: EimsConfig): EimsSellerDetails {
    const fallback = buildEimsSeller(cfg);
    const e = this.cached;
    return {
      ...fallback,
      LegalName: has(fallback.LegalName) ? fallback.LegalName : (e?.LegalName ?? fallback.LegalName),
      Phone: has(fallback.Phone) ? fallback.Phone : (e?.Phone ?? fallback.Phone),
      Region: has(fallback.Region) ? fallback.Region : (e?.Region ?? fallback.Region),
      Wereda: has(fallback.Wereda) ? fallback.Wereda : (e?.Wereda ?? fallback.Wereda),
      City: has(fallback.City) ? fallback.City : (e?.City ?? fallback.City),
    };
  }

  /** Reload the cache. Concurrency-safe (see class comment); public so a caller can force one. */
  async refresh(): Promise<void> {
    if (this.refreshing) return this.refreshing;
    this.refreshing = this.doRefresh().finally(() => {
      this.refreshing = null;
    });
    return this.refreshing;
  }

  private async doRefresh(): Promise<void> {
    try {
      const cfg = this.config.get<EimsConfig>("eims")!;
      const { companyInfo, businessInfo } = await this.withTimeout(
        this.etrade.resolveCompanyData(cfg.tin),
        EimsSellerCacheService.REFRESH_TIMEOUT_MS,
      );
      if (!businessInfo) return; // no licence on file yet — keep the previous snapshot
      const data = this.etrade.extractRegistrationData(businessInfo, companyInfo);
      // e-Trade returns region/zone/woreda as names ("Addis Ababa", "Bole") — resolved through the
      // same MoR location master the buyer side uses, since the geography is objective, not
      // buyer-specific. `tryResolveMorGeo` never throws: an address MoR does not list simply
      // leaves these fields to getSellerDetails' static-config fallback, which is authoritative
      // anyway (see the class comment — MoR has already cleared the static seller values under
      // rule 7017, so nothing here may override one). e-Trade carries no country field; the
      // resolver reads a blank country as domestic, which is correct for EDR's own registration.
      const geo = tryResolveMorGeo({
        region: data.region,
        zone: data.zone,
        woreda: data.woreda,
      });
      this.cached = {
        // The *legal* entity name, not the licence's trade name that
        // `data.companyName` now carries — an EIMS seller is filed under its
        // registered name.
        LegalName:
          companyInfo?.BusinessName?.trim() || data.companyName || undefined,
        Phone: data.mobilePhone || data.regularPhone || undefined,
        Region: geo?.Region,
        Wereda: geo?.Wereda,
        City: geo?.City,
      };
    } catch (err) {
      this.logger.warn(
        `EIMS seller e-Trade refresh failed, keeping previous snapshot: ${(err as Error).message}`,
      );
    }
  }

  /**
   * `ETradeService` sets no request timeout of its own, so one is enforced here. Note this only
   * stops *waiting* on the request — nothing cancels the underlying HTTP call (no
   * `AbortController` wired into `ETradeService`), so a timed-out request may still complete in
   * the background; its result is simply never read.
   */
  private withTimeout<T>(promise: Promise<T>, ms: number): Promise<T> {
    return new Promise<T>((resolve, reject) => {
      const timer = setTimeout(() => reject(new Error(`e-Trade lookup timed out after ${ms}ms`)), ms);
      promise.then(
        (value) => {
          clearTimeout(timer);
          resolve(value);
        },
        (err) => {
          clearTimeout(timer);
          reject(err);
        },
      );
    });
  }
}