import { apiRaw } from "../api/client";

const MAX = 600;
const cache = new Map<string, Promise<string>>(); // 插入序 ≈ LRU(命中时重插)

// 带鉴权取图 → objectURL。后端 Bearer-only,<img>/<iframe> 直挂 /api 必 401,
// 故图片一律走此通道;URL 含内容 hash 不可变,会话内可安全长驻缓存。
export async function fetchObjectUrl(url: string, signal?: AbortSignal): Promise<string> {
  const hit = cache.get(url);
  if (hit) {
    cache.delete(url);
    cache.set(url, hit);
    return hit;
  }
  const p = (async () => {
    const res = await apiRaw(url, { signal });
    return URL.createObjectURL(await res.blob());
  })();
  p.catch(() => cache.delete(url)); // 失败出缓存,下次调用重试
  cache.set(url, p);
  while (cache.size > MAX) {
    const oldest = cache.keys().next().value as string;
    cache.delete(oldest); // 不 revoke:可能仍被在屏 <img> 引用;≤600 条会话内 blob 可接受
  }
  return p;
}

export function __resetImageCache(): void {
  cache.clear();
}