const SESSION_KEY = 'dukang_session_id';

type WxStorage = {
  getStorageSync?: (key: string) => unknown;
  setStorageSync?: (key: string, value: unknown) => void;
};

function getWxStorage(): WxStorage | undefined {
  return (globalThis as { wx?: WxStorage }).wx;
}

function readStorage(key: string): string | null {
  if (typeof localStorage !== 'undefined') {
    return localStorage.getItem(key);
  }
  try {
    const v = getWxStorage()?.getStorageSync?.(key);
    return v != null && v !== '' ? String(v) : null;
  } catch {
    return null;
  }
}

function writeStorage(key: string, value: string): void {
  if (typeof localStorage !== 'undefined') {
    localStorage.setItem(key, value);
    return;
  }
  try {
    getWxStorage()?.setStorageSync?.(key, value);
  } catch {
    /* ignore */
  }
}

function newSessionId(): string {
  if (typeof crypto !== 'undefined' && 'randomUUID' in crypto) {
    return crypto.randomUUID();
  }
  return `s_${Date.now()}_${Math.random().toString(36).slice(2, 10)}`;
}

export function getSessionId(): string {
  let id = readStorage(SESSION_KEY);
  if (!id) {
    id = newSessionId();
    writeStorage(SESSION_KEY, id);
  }
  return id;
}

export function touchSession(): string {
  return getSessionId();
}