/**
 * @file prefsBackup.ts
 * @description Export / import of THIS browser's preferences (theme, language,
 * notification prefs, pet, sidebar, workspace layout …) as one JSON file, for
 * Settings → Data. Only allowlisted `localStorage` keys travel — never the
 * dashboard access token or a cache — and an import writes only those keys,
 * as strings, so a crafted file cannot plant anything else.
 * @author Nguyễn Ngọc Trí Vĩ <vinnt@smartgift.vn>
 */

export const PREFS_FORMAT = "agenthub-browser-prefs";

const EXACT = new Set([
  "theme",
  "i18nextLng",
  "agent-monitor-notifications",
  "dashboard_tab",
  "sidebar-collapsed",
  "agent-dashboard-sagi-enabled",
  "agent-dashboard-sagi-muted",
  "agent-dashboard-sagi-pos",
  "agenthub-data-scope",
]);

/** Whether a `localStorage` key is a preference that may be exported/imported. */
export function isPrefKey(key: string): boolean {
  return EXACT.has(key) || key.startsWith("agenthub.");
}

export interface PrefsFile {
  format: typeof PREFS_FORMAT;
  version: 1;
  exported_at: string;
  prefs: Record<string, string>;
}

/** Every preference key this browser holds. */
export function exportPrefs(): PrefsFile {
  const prefs: Record<string, string> = {};
  for (let i = 0; i < localStorage.length; i++) {
    const k = localStorage.key(i);
    if (k && isPrefKey(k)) prefs[k] = localStorage.getItem(k) ?? "";
  }
  return { format: PREFS_FORMAT, version: 1, exported_at: new Date().toISOString(), prefs };
}

/** Write a prefs file's allowlisted string values; returns how many. Throws on a foreign file. */
export function importPrefs(text: string): number {
  const data = JSON.parse(text) as Partial<PrefsFile>;
  if (!data || data.format !== PREFS_FORMAT || typeof data.prefs !== "object" || !data.prefs)
    throw new Error("not an AgentHub preferences file");
  let n = 0;
  for (const [k, v] of Object.entries(data.prefs)) {
    if (!isPrefKey(k) || typeof v !== "string") continue;
    localStorage.setItem(k, v);
    n++;
  }
  return n;
}