/**
 * @file userPrefs.ts
 * @description An account's UI preferences, kept per ACCOUNT on the server
 * (`/api/me/prefs`, docs/plans/onboarding) while every component goes on
 * reading and writing localStorage as it always did. On sign-in `hydrate()`
 * copies the account's stored values into localStorage (the account wins),
 * sends up the ones this browser has and the account does not yet, and makes
 * the theme, language and pet re-read them. From then on a write to one of
 * `PREF_KEYS` through `localStorage.setItem`/`removeItem` is sent to the
 * server, batched. `useOnboarding()` tells the setup wizard whether this
 * account has been through it. Never throws: a server that cannot answer
 * leaves the browser's own values in charge. The same row also holds
 * `agenthub.chatUi`, which `lib/chatUi.ts` reads and writes on the server
 * directly (no localStorage copy).
 * @author Nguyễn Ngọc Trí Vĩ <vinnt@smartgift.vn>
 */

import { useSyncExternalStore } from "react";
import { api } from "./api";
import i18n from "../i18n";
import { applyStoredTheme } from "../hooks/useTheme";
import { FONT_SIZE_EVENT, applyUiFontSize } from "./fontSize";

/** The localStorage keys an account's preferences are made of (server/routes/me.js). */
export const PREF_KEYS = [
  "theme",
  "agenthub.theme.dark",
  "agenthub.theme.light",
  "i18nextLng",
  "agenthub.terminal.font",
  "agenthub.terminal.fontSize",
  "agenthub.ui.fontSize",
  "agenthub.pet",
  "agenthub.pet.size",
  "agenthub.pet.names",
  "agent-dashboard-sagi-enabled",
  "agent-dashboard-sagi-muted",
  "agent-monitor-notifications",
  "agenthub.defaultTool",
  "agenthub.permissionMode",
  "agenthub.codex.sandbox",
  "agenthub.codex.approval",
  "agenthub.codex.bypass",
  "agenthub.tour",
  "agenthub.workspace.allTabs",
  "agenthub.markdown.view",
] as const;
const SYNCED = new Set<string>(PREF_KEYS);
const PUSH_DELAY_MS = 400;

// `forced`: Settings asked for the setup again, whatever the account has.
type State = { loaded: boolean; onboardedAt: string | null; forced: boolean };
let state: State = { loaded: false, onboardedAt: null, forced: false };
const listeners = new Set<() => void>();
const setState = (next: Partial<State>) => {
  state = { ...state, ...next };
  listeners.forEach((l) => l());
};

let pending: Record<string, string | null> = {};
let timer: ReturnType<typeof setTimeout> | undefined;
let syncing = false;

function queue(key: string, value: string | null) {
  if (!syncing) return;
  pending[key] = value;
  clearTimeout(timer);
  timer = setTimeout(flush, PUSH_DELAY_MS);
}

/** Send what is queued now (also on page hide). */
export function flush(): Promise<void> {
  clearTimeout(timer);
  const batch = pending;
  pending = {};
  if (!Object.keys(batch).length) return Promise.resolve();
  return api.me
    .savePrefs(batch)
    .then(() => undefined)
    .catch(() => {
      /* offline or signed out: the browser keeps its own copy */
    });
}

let wrapped = false;
function wrapStorage() {
  if (wrapped || typeof Storage === "undefined") return;
  wrapped = true;
  const proto = Storage.prototype;
  const setItem = proto.setItem;
  const removeItem = proto.removeItem;
  proto.setItem = function (key: string, value: string) {
    setItem.call(this, key, value);
    if (this === window.localStorage && SYNCED.has(key)) queue(key, String(value));
  };
  proto.removeItem = function (key: string) {
    removeItem.call(this, key);
    if (this === window.localStorage && SYNCED.has(key)) queue(key, null);
  };
  window.addEventListener("pagehide", () => void flush());
}

function readLocal(key: string): string | null {
  try {
    return window.localStorage.getItem(key);
  } catch {
    return null;
  }
}

/** Make what reads these keys read them again. */
function reapply(prefs: Record<string, string>) {
  // Painted now, not only on the next useTheme render: the login page wore the OS's.
  applyStoredTheme();
  window.dispatchEvent(new Event("agenthub-theme"));
  window.dispatchEvent(new Event("sagi:prefs"));
  applyUiFontSize();
  window.dispatchEvent(new Event(FONT_SIZE_EVENT));
  const lng = prefs.i18nextLng;
  if (lng && lng !== i18n.language) void i18n.changeLanguage(lng);
}

/**
 * Load the signed-in account's preferences into this browser and start
 * sending changes. Call once a login (or local mode) is known.
 */
export async function hydrate(): Promise<void> {
  syncing = false;
  pending = {};
  let answer;
  try {
    answer = await api.me.prefs();
  } catch {
    // No answer (an older server, a test with no API): no wizard, no sync —
    // the browser's own values stay in charge.
    return;
  }
  const up: Record<string, string> = {};
  for (const key of PREF_KEYS) {
    const theirs = answer.prefs[key];
    if (typeof theirs === "string") {
      try {
        window.localStorage.setItem(key, theirs);
      } catch {
        /* storage blocked */
      }
    } else {
      const mine = readLocal(key);
      if (mine !== null) up[key] = mine;
    }
  }
  wrapStorage();
  syncing = true;
  reapply(answer.prefs);
  if (Object.keys(up).length) {
    pending = { ...up };
    void flush();
  }
  setState({ loaded: true, onboardedAt: answer.onboardedAt });
}

/** The first-run setup is done or skipped, for this account. */
export async function markOnboarded(): Promise<void> {
  await flush();
  const at = new Date().toISOString();
  setState({ onboardedAt: at, forced: false });
  try {
    const r = await api.me.onboarded();
    setState({ onboardedAt: r.onboardedAt || at });
  } catch {
    /* shown again next time — better than never saving the choices */
  }
}

/** Show the setup again (Settings → System). */
export function resetOnboarding(): void {
  setState({ onboardedAt: null, forced: true });
}

const subscribe = (l: () => void) => {
  listeners.add(l);
  return () => listeners.delete(l);
};

/** `{loaded, onboardedAt, forced}` for the account signed in now. */
export function useOnboarding(): State {
  return useSyncExternalStore(subscribe, () => state);
}

/** Tests only. */
export function __resetUserPrefs(): void {
  state = { loaded: false, onboardedAt: null, forced: false };
  pending = {};
  syncing = false;
  clearTimeout(timer);
}