import { useSyncExternalStore } from "react";

// 本机界面偏好(设置 → 界面):只影响当前浏览器,存 localStorage;读写失败(隐私模式、禁用存储)时用默认值。

export type UiPrefs = {
  /** 技术信息(ID、hash、token、耗时、原始字段、内部状态码)默认展开 */
  techInfoExpanded: boolean;
};

const KEY = "umt.ui-prefs";
const DEFAULTS: UiPrefs = { techInfoExpanded: false };
const listeners = new Set<() => void>();
let cache: UiPrefs | null = null;

function read(): UiPrefs {
  if (cache) return cache;
  let v: UiPrefs = DEFAULTS;
  try {
    const raw = typeof localStorage === "undefined" ? null : localStorage.getItem(KEY);
    if (raw) v = { ...DEFAULTS, ...(JSON.parse(raw) as Partial<UiPrefs>) };
  } catch {
    v = DEFAULTS;
  }
  cache = v;
  return v;
}

export function setUiPref<K extends keyof UiPrefs>(key: K, value: UiPrefs[K]) {
  cache = { ...read(), [key]: value };
  try {
    localStorage.setItem(KEY, JSON.stringify(cache));
  } catch {
    // 存不下就只在本次会话生效
  }
  for (const l of listeners) l();
}

function subscribe(l: () => void) {
  listeners.add(l);
  const onStorage = (e: StorageEvent) => {
    if (e.key !== KEY) return;
    cache = null;
    l();
  };
  if (typeof window !== "undefined") window.addEventListener("storage", onStorage);
  return () => {
    listeners.delete(l);
    if (typeof window !== "undefined") window.removeEventListener("storage", onStorage);
  };
}

export function useUiPrefs(): UiPrefs {
  return useSyncExternalStore(subscribe, read, () => DEFAULTS);
}

/** 本地记住的折叠状态(计划页分组等):key → 是否展开;读写失败时返回 null */
export function readCollapseState(key: string): Record<string, boolean> | null {
  try {
    const raw = localStorage.getItem(key);
    return raw ? (JSON.parse(raw) as Record<string, boolean>) : null;
  } catch {
    return null;
  }
}

export function writeCollapseState(key: string, v: Record<string, boolean>) {
  try {
    localStorage.setItem(key, JSON.stringify(v));
  } catch {
    // 忽略
  }
}