export type ReferenceAccess = "reachable" | "unreachable" | "unknown";

export async function validateVideoReferences(
  input: unknown,
  probe: (url: string) => Promise<ReferenceAccess>,
): Promise<{ images: string[]; error?: string; status?: number }> {
  if (input === undefined) return { images: [] };
  if (!Array.isArray(input) || input.length > 8) return { images: [], error: "请提供不超过 8 张参考图", status: 400 };
  const images: string[] = [];
  for (const value of input) {
    try {
      if (typeof value !== "string") throw new Error();
      const parsed = new URL(value.trim());
      if (!["http:", "https:"].includes(parsed.protocol) || parsed.username || parsed.password) throw new Error();
      images.push(value.trim());
    } catch {
      return { images: [], error: "参考图地址无效，请重新上传", status: 400 };
    }
  }
  const checks = await Promise.all([...new Set(images)].map(url => probe(url).catch(() => "unknown" as const)));
  if (checks.includes("unreachable")) return { images: [], error: "参考图片链接已失效或无访问权限，请重新上传", status: 400 };
  if (checks.includes("unknown")) return { images: [], error: "参考图片连接暂时超时或服务繁忙，请重试；尚未提交生成任务", status: 503 };
  // First and last frames are positional; identical URLs must remain two entries.
  return { images };
}