// 零依赖 OSS 客户端(通用安装、无服务端项目时的回退实现):
// OSS ListObjectsV2 + V1 签名(Header Authorization: OSS AK:SIG),与 server/services/oss-client.js 行为对齐
// 凭据只从进程环境读取(scripts/oss.mjs 已先 loadEnv 注入),本模块不含任何密钥
import crypto from 'crypto';

export function ossConfig() {
  return {
    bucket: process.env.OSS_BUCKET || '',
    region: process.env.OSS_REGION || '',
    accessKeyId: process.env.OSS_ACCESS_KEY_ID || '',
    accessKeySecret: process.env.OSS_ACCESS_KEY_SECRET || '',
  };
}

export function ossEnabled() {
  const c = ossConfig();
  return Boolean(c.bucket && c.region && c.accessKeyId && c.accessKeySecret);
}

/** 公开读直链域名: 默认桶默认域名(oss-<region>.aliyuncs.com),配 OSS_PUBLIC_DOMAIN 可切换(同服务端规则) */
export function publicDomain() {
  const c = ossConfig();
  return (process.env.OSS_PUBLIC_DOMAIN || `${c.bucket}.oss-${c.region}.aliyuncs.com`).replace(/^https?:\/\//, '');
}

function xmlDecode(s) {
  return String(s)
    .replace(/&amp;/g, '&').replace(/&lt;/g, '<').replace(/&gt;/g, '>')
    .replace(/&quot;/g, '"').replace(/&apos;/g, "'")
    .replace(/&#x([0-9a-f]+);/gi, (m, n) => { try { return String.fromCharCode(parseInt(n, 16)); } catch { return m; } })
    .replace(/&#(\d+);/g, (m, n) => { try { return String.fromCharCode(Number(n)); } catch { return m; } });
}

function xmlTag(text, name) {
  const m = new RegExp(`<${name}>([\\s\\S]*?)<\\/${name}>`).exec(text);
  return m ? xmlDecode(m[1]) : null;
}

// 与 ali-oss 一致的 V1 签名:
// - canonicalized resource = /bucket/ + (?continuation-token=<原值> 仅当存在) —— continue-token 是子资源
// - list-type/max-keys/prefix 为普通 query,不参与签名,只在请求 URL 中 percent 编码
// - 日期走 x-oss-date 头(GMT)
export async function _listPage(params, token) {
  const c = ossConfig();
  const date = new Date().toUTCString();
  const urlQ = Object.entries(params)
    .map(([k, v]) => `${encodeURIComponent(k)}=${encodeURIComponent(v)}`)
    .concat(token ? [`continuation-token=${encodeURIComponent(token)}`] : [])
    .join('&');
  const canonicalResource = `/${c.bucket}/${token ? `?continuation-token=${token}` : ''}`;
  const stringToSign = ['GET', '', '', date, `x-oss-date:${date}`, canonicalResource].join('\n');
  const sig = crypto.createHmac('sha1', c.accessKeySecret).update(stringToSign).digest('base64');
  const url = `https://${c.bucket}.oss-${c.region}.aliyuncs.com/?${urlQ}`;
  const res = await fetch(url, {
    headers: { 'x-oss-date': date, Authorization: `OSS ${c.accessKeyId}:${sig}` },
  });
  if (!res.ok) throw new Error(`OSS 列举失败 HTTP ${res.status}: ${(await res.text()).slice(0, 200)}`);
  return await res.text();
}

/** 列举桶内对象(prefix 为空=全桶),与 server/services/oss-client.js listObjects 返回结构一致 */
export async function listObjects(prefix = '') {
  const objects = [];
  let token = null;
  for (;;) {
    const params = prefix ? { 'list-type': '2', 'max-keys': '1000', prefix } : { 'list-type': '2', 'max-keys': '1000' };
    const text = await _listPage(params, token);
    const contents = new RegExp('<Contents>([\\s\\S]*?)<\\/Contents>', 'g');
    let m;
    while ((m = contents.exec(text))) {
      const size = Number(xmlTag(m[1], 'Size')) || 0;
      const last = xmlTag(m[1], 'LastModified');
      objects.push({
        name: xmlTag(m[1], 'Key'),
        size,
        lastModified: last ? new Date(last).toISOString() : null,
      });
    }
    if (xmlTag(text, 'IsTruncated') !== 'true') break;
    token = xmlTag(text, 'NextContinuationToken');
    if (!token) break;
  }
  return objects;
}