/**
 * @file backupAutomat.js
 * @description Manages backup status, archive listings, and VFS file recovery from backup archives (`GET /backup`, `GET /backup/:id/vfs`, `POST /backup/:id/vfs/recover`).
 *
 * Upstream Triggers:
 * - `authAutomat`: Subscribes to auth state changes — calls `actions.load()` on
 *   `'authed'` with a `selectedCompanyId`, and `actions.clear()` on `'anon'`.
 * - `sseAutomat`: Subscribes to `'backup'` event (if dispatched) to reload silently.
 * - UI / Settings: Calls to `actions.load()`, `actions.reload()`, `actions.listBackupVfs()`, or `actions.recoverBackupVfs()`.
 */

import { Automat } from 'react-automat';
import { backup as backupApi } from '../api';
import authAutomat from './authAutomat';
import sseAutomat from './sseAutomat';

/**
 * @typedef {Object} BackupItem
 * @property {string} name Archive file or directory name
 * @property {string} path Full storage path
 * @property {number} totalSizeBytes Total size in bytes
 * @property {string|null} timestamp Creation timestamp
 * @property {object|null} [manifest] Backup manifest details
 */

/**
 * @typedef {Object} BackupStatus
 * @property {boolean} enabled Whether automated backups are enabled
 * @property {boolean} isRunning Whether a backup is currently executing
 * @property {string} dbProvider Database provider name (e.g. 'sqlite', 'mssql')
 * @property {boolean} mssqlWarning Whether an MSSQL warning is present
 * @property {string} backupDir Root directory where backups are stored
 * @property {{ hourlyMax: number, dailyMax: number, monthly: string }} retention Retention configuration
 * @property {{ hourly: number, daily: number, monthly: number }} counts Counts of existing backups
 * @property {BackupItem|null} [latestHourly] Most recent hourly backup
 * @property {BackupItem|null} [latestDaily] Most recent daily backup
 * @property {BackupItem|null} [latestMonthly] Most recent monthly backup
 */

/**
 * @typedef {Object} BackupState
 * @property {'idle'|'loading'|'ready'|'failed'} status Load lifecycle state
 * @property {string|null} error Last error message
 * @property {BackupStatus|null} backupStatus Service status and retention settings
 * @property {{ counts: { hourly: number, daily: number, monthly: number }, hourly: BackupItem[], daily: BackupItem[], monthly: BackupItem[] }} backups Grouped backup archives
 * @property {Record<string, Array<{ name: string, size: number, mime: string, mtime: string }>>} vfsFilesByBackup
 * @property {Record<string, boolean>} vfsLoadingByBackup
 */

/** @type {BackupState} */
const initialState = {
  status: 'idle',
  error: null,
  backupStatus: null,
  backups: {
    counts: { hourly: 0, daily: 0, monthly: 0 },
    hourly: [],
    daily: [],
    monthly: [],
  },
  vfsFilesByBackup: {},
  vfsLoadingByBackup: {},
};

let backupAutomat;
let inflightLoad = null;

// #region fetch
// MARK: calls GET /api/backup from ./api/index.js
async function fetchBackupData() {
  const data = await backupApi.getStatus();
  const status = data?.status ?? null;
  const rawBackups = data?.backups ?? {};

  const hourly = Array.isArray(rawBackups.hourly) ? rawBackups.hourly : [];
  const daily = Array.isArray(rawBackups.daily) ? rawBackups.daily : [];
  const monthly = Array.isArray(rawBackups.monthly) ? rawBackups.monthly : [];

  const counts = rawBackups.counts ?? {
    hourly: hourly.length,
    daily: daily.length,
    monthly: monthly.length,
  };

  return {
    backupStatus: status,
    backups: {
      counts,
      hourly,
      daily,
      monthly,
    },
  };
}
// #endregion

const actions = {
  // #region load
  // MARK: calls GET /api/backup from ./api/index.js
  /**
   * Loads backup status and archive listing.
   * Deduplicates concurrent callers.
   *
   * @param {boolean} [silent=false] If true, keeps status as 'ready' without flashing 'loading'
   * @returns {Promise<{ backupStatus: BackupStatus|null, backups: object }>}
   */
  load(silent = false) {
    if (inflightLoad) return inflightLoad;
    if (!silent) {
      backupAutomat.setState({ status: 'loading', error: null });
    }
    inflightLoad = (async () => {
      try {
        const { backupStatus, backups } = await fetchBackupData();
        backupAutomat.setState({
          backupStatus,
          backups,
          status: 'ready',
          error: null,
        });
        return { backupStatus, backups };
      } catch (err) {
        const error = err?.message ?? String(err);
        backupAutomat.setState(silent ? { error } : { status: 'failed', error });
        throw err;
      } finally {
        inflightLoad = null;
      }
    })();
    return inflightLoad;
  },
  // #endregion

  // #region reload
  // MARK: calls GET /api/backup from ./api/index.js
  /**
   * Silently re-fetches backup status and archives in the background.
   */
  async reload() {
    return actions.load(true);
  },
  // #endregion

  // #region listBackupVfs
  // MARK: calls GET /api/backup/:id/vfs from ./api/index.js
  /**
   * Retrieves the list of VFS files stored inside a specific backup.
   *
   * @param {string} backupId Identifier of the backup
   * @param {number} [companyId] Optional company ID override
   * @returns {Promise<Array<{ name: string, size: number, mime: string, mtime: string }>>}
   */
  async listBackupVfs(backupId, companyId) {
    if (!backupId) return [];
    backupAutomat.setState({
      vfsLoadingByBackup: { ...backupAutomat.state.vfsLoadingByBackup, [backupId]: true },
    });
    try {
      const res = await backupApi.listVfs(backupId, companyId);
      const files = Array.isArray(res?.files) ? res.files : [];
      backupAutomat.setState({
        vfsFilesByBackup: { ...backupAutomat.state.vfsFilesByBackup, [backupId]: files },
      });
      return files;
    } finally {
      backupAutomat.setState({
        vfsLoadingByBackup: { ...backupAutomat.state.vfsLoadingByBackup, [backupId]: false },
      });
    }
  },
  // #endregion

  // #region recoverBackupVfs
  // MARK: calls POST /api/backup/:id/vfs/recover from ./api/index.js
  /**
   * Restores a single VFS file from the specified backup into the active VFS.
   *
   * @param {string} backupId Identifier of the backup
   * @param {string} path Relative file path within the VFS
   * @param {number} [companyId] Optional company ID override
   * @returns {Promise<object>} Recovery result
   */
  async recoverBackupVfs(backupId, path, companyId) {
    return backupApi.recoverVfs(backupId, path, companyId);
  },
  // #endregion

  /**
   * Resets the automat state to initial empty values.
   */
  clear() {
    backupAutomat.setState({ ...initialState });
  },
};

backupAutomat = new Automat(initialState, actions, { name: 'backup' });

// #region sseListener
if (sseAutomat?.actions?.on) {
  sseAutomat.actions.on('backup', () => {
    void backupAutomat.actions.reload().catch(() => {});
  });
}
// #endregion

// #region authSync
function authKey(authState) {
  if (authState?.status !== 'authed' || !authState.user) return null;
  const companyId = authState.user.selectedCompanyId;
  return companyId == null ? null : String(companyId);
}

let lastAuthKey;
function syncWithAuth(authState) {
  const key = authKey(authState);
  if (key === lastAuthKey) return;
  lastAuthKey = key;
  if (key == null) {
    backupAutomat.actions.clear();
  } else {
    void backupAutomat.actions.load().catch(() => {});
  }
}

authAutomat.subscribe(syncWithAuth);
syncWithAuth(authAutomat.state);
// #endregion

export default backupAutomat;