// utils/uuid.js
export function generateUUIDv4() {
  // 优先使用 crypto（更安全），MiniProgram / H5 / Node 环境可能都支持
  if (typeof crypto !== 'undefined' && crypto.getRandomValues) {
    const buf = new Uint8Array(16);
    crypto.getRandomValues(buf);
    // Per RFC4122 v4
    buf[6] = (buf[6] & 0x0f) | 0x40;
    buf[8] = (buf[8] & 0x3f) | 0x80;
    const hex = Array.from(buf).map(b => b.toString(16).padStart(2, '0')).join('');
    return `${hex.substr(0,8)}-${hex.substr(8,4)}-${hex.substr(12,4)}-${hex.substr(16,4)}-${hex.substr(20,12)}`;
  } else {
    // 备用（兼容性）：Math.random 实现（伪随机，注意安全性）
    let d = new Date().getTime();
    if (typeof performance !== 'undefined' && typeof performance.now === 'function'){
      d += performance.now(); // 更好的熵
    }
    return 'xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx'.replace(/[xy]/g, c => {
      const r = (d + Math.random()*16) % 16 | 0;
      d = Math.floor(d/16);
      return (c === 'x' ? r : (r & 0x3 | 0x8)).toString(16);
    });
  }
}