错误处理与避坑

// 审核关键词（小写匹配）。同一个逻辑错误会有多种文案变体，中英都要覆盖
const MODERATION_KEYWORDS = [
  'violate our guardrails', 'may violate our content polic', 'violated our content polic',
  'content policy', 'content_policy_violation', 'safety polic', 'blocked by safety',
  'appear to be unsafe', 'appears to be unsafe', 'flagged as sensitive', 'nsfw',
  'moderation_blocked', 'result of our safety system', "i can't help with", 'i cannot help with',
  '安全政策', '内容政策', '防护限制', '色情', '裸露', '不能帮助', '无法用于生成', '违反了我们的',
];
const MODERATION_REGEXES = [/\be005\b/];   // ← 词边界，别改成 includes（见规则二）

// ★ 必须先跑：真故障穿着 400 的皮
const TRANSIENT_400 = [/timeout|timed out|超时/, /unknown internal error|internal server error/];

const BAD_REQUEST  = [/不合法的size/, /size must be/, /invalid size/, /model .{0,64} not found/, /提示词太模糊/];
const SOURCE_IMAGE = [/invalid image file/, /unsupported image format/, /image format .* not supported/, /无法解码/];

export async function buildUpstreamError(resp) {
  let raw = '';
  try { raw = await resp.text(); } catch { /* body 读不出就只按状态码判 */ }
  // ★ 分类要跑完整 body，截断只用于打日志
  const body = raw.toLowerCase();
  const s = resp.status;

  const mk = (kind, retryable) =>
    Object.assign(new Error(`[${kind}] ${s}: ${raw.slice(0, 300)}`), { kind, status: s, retryable });

  if (s === 401 || s === 403) return mk('AUTH', false);
  if (s === 402)              return mk('INSUFFICIENT_BALANCE', false);
  if (s === 429)              return mk('RATE_LIMITED', true);
  if (s >= 500)               return mk('UPSTREAM_5XX', true);
  if (s === 451)              return mk('CONTENT_MODERATED', false);   // 状态码级判定，不看正文

  if (s === 400) {
    if (TRANSIENT_400.some((re) => re.test(body)))  return mk('UPSTREAM_TRANSIENT', true);   // ← 必须第一个
    if (SOURCE_IMAGE.some((re) => re.test(body)))   return mk('BAD_SOURCE_IMAGE', false);
    if (MODERATION_KEYWORDS.some((k) => body.includes(k))
        || MODERATION_REGEXES.some((re) => re.test(body)))
                                                    return mk('CONTENT_MODERATED', false);
    if (BAD_REQUEST.some((re) => re.test(body)))    return mk('INVALID_REQUEST', false);
    return mk('UNKNOWN_4XX', true);   // 认不出的 4xx 允许重试，理由见下文
  }
  return mk('UNKNOWN', false);
}

const sleep = (ms) => new Promise((r) => setTimeout(r, ms));

export async function withRetry(fn, { max = 3 } = {}) {
  let last;
  for (let attempt = 1; attempt <= max; attempt++) {
    try { return await fn(); }
    catch (err) {
      last = err;
      const retryable = err?.retryable === true
        || err?.name === 'TimeoutError' || err?.name === 'AbortError';   // fetch 超时
      if (!retryable || attempt === max) throw err;
      const base = err?.kind === 'RATE_LIMITED' ? 15_000 : 3_000;
      await sleep(base * 2 ** (attempt - 1) + Math.random() * 2_000);    // 指数退避 + 抖动
    }
  }
  throw last;
}