import OSS from 'ali-oss';

let client: OSS | null = null;

function getClient(): OSS {
  if (client) return client;
  const region = process.env.OSS_REGION || 'oss-cn-shanghai';
  const accessKeyId = process.env.OSS_ACCESS_KEY_ID || '';
  const accessKeySecret = process.env.OSS_ACCESS_KEY_SECRET || '';
  const bucket = process.env.OSS_BUCKET || '';
  if (!accessKeyId || !accessKeySecret || !bucket) {
    throw new Error('OSS 未配置：OSS_ACCESS_KEY_ID / OSS_ACCESS_KEY_SECRET / OSS_BUCKET');
  }
  client = new OSS({ region, accessKeyId, accessKeySecret, bucket, secure: true });
  return client;
}

function safeExt(filename: string, fallback = 'png'): string {
  const m = /\.([a-zA-Z0-9]{1,8})$/.exec(filename);
  return m ? m[1].toLowerCase() : fallback;
}

function randId(len = 8): string {
  return Math.random().toString(36).slice(2, 2 + len);
}

/** 上传 buffer 到 OSS，返回公开访问的 URL */
export async function uploadFeedbackImage(filename: string, buf: Buffer, mimetype: string): Promise<string> {
  const c = getClient();
  const baseDir = (process.env.OSS_BASE_DIR || '/dos').replace(/^\/+|\/+$/g, '');
  const ymd = new Date().toISOString().slice(0, 10);
  const key = `${baseDir}/feedback/${ymd}/${Date.now().toString(36)}-${randId()}.${safeExt(filename, mimetype.split('/')[1] || 'png')}`;
  await c.put(key, buf, {
    headers: { 'Content-Type': mimetype, 'x-oss-object-acl': 'public-read' },
  });
  const host = (process.env.OSS_HOST || `https://${process.env.OSS_BUCKET}.${process.env.OSS_ENDPOINT}/`).replace(/\/+$/, '/');
  return host + key;
}