import { readdirSync } from 'node:fs';
import { statSync } from 'node:fs';
import { join } from 'node:path';

import {
  BadRequestException,
  ConflictException,
  Injectable,
  NotFoundException,
} from '@nestjs/common';
import {
  BACKUP_COMMAND_CHANNEL,
  archiveFileName,
  backupIdTime,
  dumpFileName,
  listSets,
  remoteBundleId,
  type BackupCommand,
  type BackupConnectionTestInput,
  type BackupConnectionTestResult,
  type BackupRestoreInput,
  type BackupSetView,
  type BackupSetsView,
  type BackupSettingsInput,
  type BackupSettingsView,
} from '@dorfteich/shared';
import { webdavList } from '@dorfteich/shared/webdav';
import { User } from '@prisma/client';

import { AuditService } from '../audit/audit.service';
import { BackupTargetService } from '../backup/backup-target.service';
import { MaintenanceStateService } from '../backup/maintenance-state.service';
import { AppConfig } from '../config/app-config.service';
import { PrismaService } from '../prisma/prisma.service';
import { InstanceSettingsService } from '../settings/instance-settings.service';

/**
 * Site-Admin backup management (issue #103): the Nextcloud target
 * configuration, manual "back up now", the restore picker (local sets from
 * the read-only backups mount, remote sets via WebDAV), and the restore
 * trigger. The sidecar does the actual work — commands travel over the
 * {@link BACKUP_COMMAND_CHANNEL} NOTIFY bus, progress comes back through
 * `status.json`/`restore-status.json`.
 */
@Injectable()
export class BackupAdminService {
  constructor(
    private readonly target: BackupTargetService,
    private readonly maintenance: MaintenanceStateService,
    private readonly settings: InstanceSettingsService,
    private readonly prisma: PrismaService,
    private readonly audit: AuditService,
    private readonly config: AppConfig,
  ) {}

  settingsView(): Promise<BackupSettingsView> {
    return this.target.settingsView();
  }

  /**
   * Persists the backup settings. When the Nextcloud side is enabled, the
   * connection is live-tested first (with the new password if provided,
   * else the stored one) — like the setup wizard's SMTP step, nothing is
   * saved on failure.
   */
  async saveSettings(input: BackupSettingsInput, actor: User): Promise<BackupSettingsView> {
    if (input.nextcloud.enabled) {
      this.assertTargetAllowed(input.nextcloud.baseUrl);
      const test = await this.target.testConnection({
        baseUrl: input.nextcloud.baseUrl,
        username: input.nextcloud.username,
        folder: input.nextcloud.folder,
        password: input.nextcloud.password,
      });
      if (!test.ok) {
        throw new BadRequestException({
          code: 'backup_connection_failed',
          details: { nextcloud: [test.error ?? 'connection failed'] },
        });
      }
    }
    await this.target.storePassword(input.nextcloud.password ?? '');
    await this.settings.set('backup.localRetentionDays', input.localRetentionDays, actor.id);
    await this.settings.set('backup.remoteRetentionDays', input.remoteRetentionDays, actor.id);
    await this.settings.set('backup.nextcloud.enabled', input.nextcloud.enabled, actor.id);
    await this.settings.set('backup.nextcloud.baseUrl', input.nextcloud.baseUrl, actor.id);
    await this.settings.set('backup.nextcloud.username', input.nextcloud.username, actor.id);
    await this.settings.set('backup.nextcloud.folder', input.nextcloud.folder, actor.id);
    await this.settings.set(
      'backup.nextcloud.uploadSchedule',
      input.nextcloud.uploadSchedule,
      actor.id,
    );
    // settings.set audits each key; one summary entry names the intent.
    await this.audit.record({
      action: 'backup.settings_changed',
      actorId: actor.id,
      details: { nextcloudEnabled: input.nextcloud.enabled },
    });
    return this.settingsView();
  }

  testConnection(input: BackupConnectionTestInput): Promise<BackupConnectionTestResult> {
    // Policy first (issue #192): the "test connection" button must not be
    // usable as an egress probe towards non-allowlisted hosts.
    this.assertTargetAllowed(input.baseUrl);
    return this.target.testConnection(input);
  }

  /**
   * Deploy-level target policy (issue #192, ADR 0026): an empty
   * `BACKUP_ALLOWED_TARGETS` disables remote targets outright; a host
   * outside the list is rejected with an admin-visible error.
   */
  private assertTargetAllowed(baseUrl: string): void {
    if (!this.target.remoteAllowed()) {
      throw new BadRequestException({ code: 'backup_remote_disabled_by_policy' });
    }
    if (!this.target.targetAllowed(baseUrl)) {
      throw new BadRequestException({
        code: 'backup_target_not_allowed',
        details: { nextcloud: [`host is not in BACKUP_ALLOWED_TARGETS`] },
      });
    }
  }

  /** Both restore sources for the picker: newest first. */
  async sets(): Promise<BackupSetsView> {
    const local = this.localSets();
    const target = await this.target.resolveTarget();
    if (!target) return { local, remoteConfigured: false, remote: [] };

    const listed = await webdavList(target);
    if (!listed.ok) {
      return { local, remoteConfigured: true, remote: [], remoteError: listed.error };
    }
    const remote = listed.value
      .filter((entry) => !entry.isCollection)
      .map((entry) => ({ id: remoteBundleId(entry.name), sizeBytes: entry.sizeBytes }))
      .filter((entry): entry is { id: string; sizeBytes: number | null } => entry.id !== null)
      .map((entry) => this.setView(entry.id, entry.sizeBytes))
      .sort((a, b) => b.backupId.localeCompare(a.backupId));
    return { local, remoteConfigured: true, remote };
  }

  /** "Back up now": dump + upload, executed by the sidecar (202-style). */
  async requestRun(actor: User): Promise<void> {
    await this.notify({ kind: 'run', requestedBy: actor.username });
    await this.audit.record({ action: 'backup.run_triggered', actorId: actor.id });
  }

  /**
   * Requests an in-app restore. The type-to-confirm value must repeat the
   * backup id — the UI enforces it too, this is the server-side backstop
   * for the most destructive action the instance has.
   */
  async requestRestore(input: BackupRestoreInput, actor: User): Promise<void> {
    if (input.confirm !== input.backupId) {
      throw new BadRequestException({ code: 'backup_restore_confirm_mismatch' });
    }
    if (this.maintenance.current()?.state === 'running' && this.maintenance.isActive()) {
      throw new ConflictException({ code: 'backup_restore_running' });
    }
    if (input.source === 'remote') {
      const target = await this.target.resolveTarget();
      if (!target) throw new BadRequestException({ code: 'backup_remote_not_configured' });
      const listed = await webdavList(target);
      const exists =
        listed.ok && listed.value.some((entry) => remoteBundleId(entry.name) === input.backupId);
      if (!exists) throw new NotFoundException({ code: 'backup_set_not_found' });
    } else {
      const complete = this.localSets().some((set) => set.backupId === input.backupId);
      if (!complete) throw new NotFoundException({ code: 'backup_set_not_found' });
    }
    await this.notify({
      kind: 'restore',
      source: input.source,
      backupId: input.backupId,
      requestedBy: actor.username,
    });
    await this.audit.record({
      action: 'backup.restore_requested',
      actorId: actor.id,
      targetType: 'backup',
      targetId: input.backupId,
      details: { source: input.source },
    });
  }

  private async notify(command: BackupCommand): Promise<void> {
    await this.prisma
      .$executeRaw`SELECT pg_notify(${BACKUP_COMMAND_CHANNEL}, ${JSON.stringify(command)})`;
  }

  /** Complete sets on the read-only backups mount, newest first. */
  private localSets(): BackupSetView[] {
    let names: string[];
    try {
      names = readdirSync(this.config.env.BACKUPS_DIR);
    } catch {
      return [];
    }
    return listSets(names)
      .filter((set) => set.complete)
      .map((set) => {
        let sizeBytes: number | null = 0;
        for (const file of [dumpFileName(set.id), archiveFileName(set.id)]) {
          try {
            sizeBytes = (sizeBytes ?? 0) + statSync(join(this.config.env.BACKUPS_DIR, file)).size;
          } catch {
            sizeBytes = null;
          }
        }
        return this.setView(set.id, sizeBytes);
      })
      .sort((a, b) => b.backupId.localeCompare(a.backupId));
  }

  private setView(backupId: string, sizeBytes: number | null): BackupSetView {
    return {
      backupId,
      startedAt: backupIdTime(backupId)?.toISOString() ?? new Date(0).toISOString(),
      sizeBytes,
    };
  }
}