import { ConflictException, Injectable, Logger, Optional } from '@nestjs/common';
import { CryptoService } from '../crypto/crypto.service';
import { ExchangeInboxProvider } from '../inbox/exchange-inbox.provider';
import { ImapProvider } from '../inbox/imap.provider';
import type { InboxConfig, InboxProvider } from '../inbox/inbox-provider.interface';

import { PrismaService } from '../prisma/prisma.service';
import { forTenant } from '../prisma/prisma-tenant.extension';
import { prismaErrorCode } from '../prisma/prisma-error';
import type { TenderEmailConfigDto } from './dto/tender-email-config.dto';

/**
 * Prisma select for TenderEmailConfig — never includes encryptedInboxCreds.
 * T-07-12: Encrypted credential blob is excluded from all API responses.
 */
const EMAIL_CONFIG_SAFE_SELECT = {
  id: true,
  userId: true,
  tenantId: true,
  protocol: true,
  host: true,
  port: true,
  encryption: true,
  folder: true,
  senderFilter: true,
  domain: true,
  isActive: true,
  createdAt: true,
  updatedAt: true,
  // encryptedInboxCreds: NEVER included — T-07-12
} as const;

/**
 * TenderEmailConfigService — per-USER CRUD for the portal-alert mailbox
 * config (Phase 14, Plan 03, INGEST-05/CONFIG-02, D-06/D-07; ownership
 * moved from tenant to user in Phase 17, Plan 01, D-01). Structural clone
 * of DkvService's config half (safe-select + encrypt-preserve-empty
 * semantics), mirroring the exact same pattern already proven for DKV's
 * own (separate, D-03) mailbox config.
 *
 * Ownership (Phase 17, D-01): a mailbox belongs to exactly one user
 * (`userId @unique`) — two users at the same tenant each connect their own
 * inbox independently, neither can read or overwrite the other's config.
 * `tenantId` stays denormalized on every row (SMTP resolution, same role as
 * `tenantId` on TenderMatch) and is written on both create and update,
 * since a user's tenant can in principle change.
 *
 * Mandantengebunden (WINDOWS #20 Etappe 2, 260909-laa): every read/write
 * below runs through `forTenant()`. Because `userId` alone (not
 * `(userId, tenantId)`) is the row's unique key, a user whose stored
 * `tenantId` has gone stale sees their OWN row become invisible under the
 * now-bound context — `getConfigForApi`/`testConnection` then correctly
 * report "no mailbox configured" (safe direction, no cross-tenant leak),
 * and a bound `saveConfig` upsert on that stale row hits the platform-wide
 * uniqueness constraint on `userId` and surfaces as a translated
 * ConflictException, not a raw 500 (T-LAA-07, Befund F, Aufgabe 1).
 *
 * Benutzerdimension seit 20260911120000 (Etappe 3b, 260911-nke): every
 * `forTenant()` call above also passes `userId` as the third argument, so
 * the `tenant_isolation_policy` on TenderEmailConfig ALSO enforces
 * `userId = current_user_id()` — a second net, not a replacement for the
 * `userId @unique` ownership model above.
 *
 * Security:
 * - T-07-12: encryptedInboxCreds is excluded from every read-path select;
 *   getConfigForApi returns `hasPassword: boolean` instead of the password.
 * - T-05-13: decrypted credentials only ever exist within a method's local
 *   scope — never logged.
 * - T-17-01: userId/tenantId are supplied by the caller from the auth
 *   context (TendersController.extractTriageContext) — this service never
 *   derives ownership from anything the DTO carries.
 *
 * This service is used ONLY by the GET/PUT /email-config routes
 * (TendersController). EmailAlertAdapter's own poll-time fan-out decrypts
 * credentials independently via a direct CryptoService injection
 * (RESEARCH.md Pattern 1) — it does NOT go through this service, since the
 * adapter's cross-tenant `findMany({where:{isActive:true}})` read is a
 * deliberate platform-scheduler exception (see EmailAlertAdapter's
 * docstring), structurally different from this service's per-user CRUD.
 */
@Injectable()
export class TenderEmailConfigService {
  private readonly logger = new Logger(TenderEmailConfigService.name);

  constructor(
    private readonly prisma: PrismaService,
    private readonly crypto: CryptoService,
    /**
     * Appended as OPTIONAL trailing constructor params (Quick 260907-let) —
     * preserves every existing `new TenderEmailConfigService(prisma,
     * crypto)` 2-arg call site in the spec unchanged. NestJS DI always
     * resolves and injects both in production (InboxModule is imported in
     * tenders.module.ts and exports both providers) — same pattern as
     * TendersController.tenderIngestionService (tenders.controller.ts).
     */
    @Optional() private readonly imapProvider?: ImapProvider,
    @Optional() private readonly exchangeProvider?: ExchangeInboxProvider,
  ) {}

  /**
   * Load config for API response: safe fields + decrypted username +
   * hasPassword flag. T-07-12: password is NEVER returned. Scoped strictly
   * by userId (T-17-01) — a user only ever reads their own mailbox.
   */
  async getConfigForApi(userId: string, tenantId: string) {
    const tenantPrisma = forTenant(this.prisma, tenantId, userId);
    const safe = await tenantPrisma.tenderEmailConfig.findUnique({
      where: { userId },
      select: EMAIL_CONFIG_SAFE_SELECT,
    });
    if (!safe) return null;

    let username: string | null = null;
    let hasPassword = false;
    try {
      const raw = await tenantPrisma.tenderEmailConfig.findUnique({ where: { userId } });
      if (raw?.encryptedInboxCreds) {
        const creds = JSON.parse(this.crypto.decrypt(raw.encryptedInboxCreds)) as {
          username?: string;
          password?: string;
        };
        username = creds.username ?? null;
        hasPassword = Boolean(creds.password);
      }
    } catch {
      /* ignore decrypt errors — return empty username, matches DkvService.getConfigForApi */
    }

    return { ...safe, username, hasPassword };
  }

  /**
   * Upsert TenderEmailConfig for a user.
   *
   * Credential handling (identical semantics to DkvService.saveConfig):
   * - dto.password non-empty: re-encrypt {username, password} together.
   * - dto.username non-empty but dto.password empty: preserve existing
   *   password, re-encrypt with the new username.
   * - both empty/undefined: preserve existing encryptedInboxCreds entirely.
   *
   * tenantId is written on both create AND update (Phase 17, D-01): it is
   * denormalized, so if the resolved tenant for this user ever changes the
   * stored value must follow.
   *
   * T-07-12: Returns safe select (no encryptedInboxCreds).
   * T-05-13: Never logs decrypted credentials.
   *
   * T-LAA-07 (Befund F): the upsert target (`userId`) has no tenant
   * dimension. A P2002 here means the caller's stale-tenant row already
   * exists and is now invisible under the bound context — translated into
   * a German ConflictException instead of a raw error (same pattern as
   * `tender-saved-search.service.ts`).
   */
  async saveConfig(ctx: { userId: string; tenantId: string }, dto: TenderEmailConfigDto) {
    const { userId, tenantId } = ctx;
    const tenantPrisma = forTenant(this.prisma, tenantId, userId);
    let encryptedInboxCreds: string | undefined;

    const credChanged =
      (dto.password && dto.password.length > 0) ||
      (dto.username !== undefined && dto.username !== null);

    if (credChanged) {
      let username: string = dto.username ?? '';
      let password: string = dto.password ?? '';

      if (!dto.password || !dto.username) {
        try {
          const existing = await tenantPrisma.tenderEmailConfig.findUnique({ where: { userId } });
          if (existing?.encryptedInboxCreds) {
            const stored = JSON.parse(this.crypto.decrypt(existing.encryptedInboxCreds)) as {
              username?: string;
              password?: string;
            };
            if (!dto.username) username = stored.username ?? '';
            if (!dto.password) password = stored.password ?? '';
          }
        } catch {
          // Ignore decrypt errors — will overwrite with whatever was provided
        }
      }

      encryptedInboxCreds = this.crypto.encrypt(JSON.stringify({ username, password }));
    }

    const data: Record<string, unknown> = {
      protocol: dto.protocol,
      encryption: dto.encryption,
      ...(dto.host !== undefined && { host: dto.host }),
      ...(dto.port !== undefined && { port: dto.port }),
      ...(dto.folder !== undefined && { folder: dto.folder }),
      ...(dto.senderFilter !== undefined && { senderFilter: dto.senderFilter }),
      ...(dto.isActive !== undefined && { isActive: dto.isActive }),
      ...(dto.domain !== undefined && { domain: dto.domain }),
      ...(encryptedInboxCreds !== undefined && { encryptedInboxCreds }),
    };

    // tenantId is written on BOTH create and update — it is denormalized
    // (Phase 17, D-01), so a user's resolved tenant must always overwrite
    // whatever was stored previously, not just be set once on create.
    try {
      return await tenantPrisma.tenderEmailConfig.upsert({
        where: { userId },
        create: { userId, tenantId, ...data },
        update: { tenantId, ...data },
        select: EMAIL_CONFIG_SAFE_SELECT,
      });
    } catch (error: unknown) {
      if (prismaErrorCode(error) === 'P2002') {
        throw new ConflictException(
          'Die Postfach-Konfiguration konnte nicht gespeichert werden, weil bereits ein widersprüchlicher Eintrag existiert. Bitte laden Sie die Seite neu und versuchen Sie es erneut.',
        );
      }
      throw error;
    }
  }

  /**
   * Tests the inbox connection using credentials from the form DTO,
   * WITHOUT persisting anything (structural clone of
   * DkvService.testConnection, dkv.service.ts:201).
   *
   * Credential fallback (T-QT16-03): a DTO field left empty falls back to
   * this SAME user's stored, decrypted credentials — never another user's
   * row, since `where: { userId }` is the only lookup key. Unlike
   * saveConfig's credChanged branching, BOTH username and password are
   * independently backfilled here (saveConfig only ever needs to backfill
   * the one field the caller didn't touch on a partial re-save; a
   * connection test with a fully blank form needs both).
   *
   * T-05-13: decrypted credentials exist only within this method's local
   * scope — never returned, never logged beyond the userId itself.
   */
  async testConnection(
    userId: string,
    tenantId: string,
    dto: TenderEmailConfigDto,
  ): Promise<{ success: boolean; message?: string }> {
    let username: string | undefined = dto.username;
    let password: string | undefined = dto.password;

    if (!username || !password) {
      try {
        const tenantPrisma = forTenant(this.prisma, tenantId, userId);
        const existing = await tenantPrisma.tenderEmailConfig.findUnique({ where: { userId } });
        if (existing?.encryptedInboxCreds) {
          const stored = JSON.parse(this.crypto.decrypt(existing.encryptedInboxCreds)) as {
            username?: string;
            password?: string;
          };
          if (!username) username = stored.username;
          if (!password) password = stored.password;
        }
      } catch {
        // T-05-13: generic — no credential details, only the userId
        this.logger.error(`testConnection: failed to load stored credentials for user ${userId}`);
      }
    }

    const inboxConfig: InboxConfig = {
      protocol: dto.protocol,
      host: dto.host ?? '',
      port: dto.port ?? 993,
      username,
      password,
      encryption: dto.encryption,
      folder: dto.folder ?? 'INBOX',
      senderFilter: dto.senderFilter,
      domain: dto.domain,
    };

    const provider: InboxProvider | undefined =
      dto.protocol === 'exchange' ? this.exchangeProvider : this.imapProvider;
    if (!provider) {
      return { success: false, message: 'Inbox-Anbieter nicht verfuegbar' };
    }

    return provider.testConnection(inboxConfig);
  }
}