/**
 * 用户ID管理工具
 * 为每个匿名用户生成永久userid并存储到localStorage
 */

const USER_ID_KEY = 'a_stock_tracker_user_id';

/**
 * 获取或生成用户ID
 * 如果localStorage中已有则返回，否则生成新的UUID
 */
export function getUserId(): string {
  if (typeof window === 'undefined') {
    return '';
  }

  let userId = localStorage.getItem(USER_ID_KEY);
  
  if (!userId) {
    // 生成UUID v4
    userId = crypto.randomUUID ? crypto.randomUUID() : generateUUID();
    localStorage.setItem(USER_ID_KEY, userId);
  }
  
  return userId;
}

/**
 * 手动生成UUID v4（兼容不支持crypto.randomUUID的环境）
 */
function generateUUID(): string {
  return 'xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx'.replace(/[xy]/g, (c) => {
    const r = Math.random() * 16 | 0;
    const v = c === 'x' ? r : (r & 0x3 | 0x8);
    return v.toString(16);
  });
}

/**
 * 更新最后访问时间
 */
export function updateLastAccessed(collectionId: number): void {
  const key = `last_accessed_${collectionId}`;
  localStorage.setItem(key, new Date().toISOString());
}

/**
 * 获取最后访问时间
 */
export function getLastAccessed(collectionId: number): string | null {
  const key = `last_accessed_${collectionId}`;
  return localStorage.getItem(key);
}