import webConfig from "@/constants/common-env";
import { getStoredAuthKey } from "@/store/auth";

type ImageBlobCacheEntry = {
  promise: Promise<Blob>;
  size: number;
  lastUsedAt: number;
};

const imageBlobCache = new Map<string, ImageBlobCacheEntry>();
const MAX_IMAGE_BLOB_CACHE_ITEMS = 8;
const MAX_IMAGE_BLOB_CACHE_BYTES = 64 * 1024 * 1024;
let imageBlobCacheBytes = 0;

function isBrowserHttps() {
  return typeof window !== "undefined" && window.location.protocol === "https:";
}

export function normalizeImageUrl(value: string) {
  const trimmed = String(value || "").trim();
  if (!trimmed) {
    return "";
  }

  try {
    const url = new URL(trimmed, typeof window !== "undefined" ? window.location.href : undefined);
    if (url.protocol === "http:" && (url.hostname.endsWith(".hf.space") || isBrowserHttps())) {
      url.protocol = "https:";
    }
    return url.toString();
  } catch {
    return trimmed;
  }
}

function isHuggingFaceHost(hostname: string) {
  const host = hostname.toLowerCase();
  return host === "huggingface.co" || host.endsWith(".hf.space") || host.endsWith(".hf.co");
}

function unproxyHuggingFaceUrl(value: string) {
  try {
    const url = new URL(value, typeof window !== "undefined" ? window.location.href : undefined);
    const marker = "/redirect_to_";
    const markerIndex = url.pathname.indexOf(marker);
    if (markerIndex < 0) {
      return "";
    }
    const target = url.pathname.slice(markerIndex + marker.length);
    const slashIndex = target.indexOf("/");
    if (slashIndex <= 0) {
      return "";
    }
    const hostname = target.slice(0, slashIndex);
    if (!isHuggingFaceHost(hostname)) {
      return "";
    }
    return `https://${hostname}${target.slice(slashIndex)}${url.search}`;
  } catch {
    return "";
  }
}

function imageFetchCandidates(src: string) {
  const normalizedSrc = normalizeImageUrl(src);
  const candidates = [normalizedSrc];
  const fallbackSrc = unproxyHuggingFaceUrl(normalizedSrc);
  if (fallbackSrc && fallbackSrc !== normalizedSrc) {
    candidates.push(fallbackSrc);
  }

  try {
    const url = new URL(normalizedSrc, typeof window !== "undefined" ? window.location.href : undefined);
    if (url.hostname === "localhost") {
      url.hostname = "127.0.0.1";
      candidates.push(url.toString());
    } else if (url.hostname === "127.0.0.1") {
      url.hostname = "localhost";
      candidates.push(url.toString());
    }
  } catch {
    // Keep the original candidate list for non-URL values.
  }

  return Array.from(new Set(candidates.filter(Boolean)));
}

async function fetchImageBlobUncached(src: string) {
  let lastError: unknown = null;
  for (const candidate of imageFetchCandidates(src)) {
    try {
      const response = await fetch(candidate, { cache: "force-cache" });
      if (response.ok) {
        return response.blob();
      }
      lastError = new Error(`HTTP ${response.status}`);
    } catch (error) {
      lastError = error;
    }
  }

  try {
    const parsed = new URL(normalizeImageUrl(src), typeof window !== "undefined" ? window.location.href : undefined);
    if (parsed.protocol === "http:" || parsed.protocol === "https:") {
      const apiBase = webConfig.apiUrl.replace(/\/$/, "");
      const authKey = await getStoredAuthKey();
      const response = await fetch(`${apiBase}/api/images/proxy?url=${encodeURIComponent(parsed.toString())}`, {
        cache: "force-cache",
        headers: authKey ? { Authorization: `Bearer ${authKey}` } : undefined,
      });
      if (response.ok) {
        return response.blob();
      }
      lastError = new Error(`HTTP ${response.status}`);
    }
  } catch (error) {
    lastError = error;
  }

  const detail = lastError instanceof Error && lastError.message ? `：${lastError.message}` : "";
  throw new Error(`读取图片失败${detail}`);
}

function evictImageBlobCache(protectedKey = "") {
  while (
    imageBlobCache.size > MAX_IMAGE_BLOB_CACHE_ITEMS ||
    imageBlobCacheBytes > MAX_IMAGE_BLOB_CACHE_BYTES
  ) {
    const candidate = [...imageBlobCache.entries()]
      .filter(([key]) => key !== protectedKey)
      .sort(([, left], [, right]) => left.lastUsedAt - right.lastUsedAt)[0];
    if (!candidate) return;
    imageBlobCache.delete(candidate[0]);
    imageBlobCacheBytes = Math.max(0, imageBlobCacheBytes - candidate[1].size);
  }
}

export async function fetchImageBlob(src: string) {
  const key = normalizeImageUrl(src);
  const cached = imageBlobCache.get(key);
  if (cached) {
    cached.lastUsedAt = Date.now();
    return cached.promise;
  }

  const entry: ImageBlobCacheEntry = {
    promise: Promise.resolve(new Blob()),
    size: 0,
    lastUsedAt: Date.now(),
  };
  entry.promise = fetchImageBlobUncached(key)
    .then((blob) => {
      if (imageBlobCache.get(key) === entry) {
        entry.size = blob.size;
        entry.lastUsedAt = Date.now();
        imageBlobCacheBytes += blob.size;
        evictImageBlobCache(key);
      }
      return blob;
    })
    .catch((error) => {
      if (imageBlobCache.get(key) === entry) {
        imageBlobCache.delete(key);
      }
      throw error;
    });
  imageBlobCache.set(key, entry);
  evictImageBlobCache(key);
  return entry.promise;
}

/**
 * 预取图片为 Blob，供「下载 / 加入参考」等需要字节流的操作用。
 *
 * ⚠️⚠️ **绝对不要在图片列表的渲染 / onLoad 路径里批量调用它**（2026-10-16 事故）。
 * 结果图是 ChatGPT 官网签名直链（跨域），`<img>` 本来就要完整下载一遍；这里再 fetch
 * 一次，跨域被 CORS 拦下后会回落到后端 `/api/images/proxy`，让只有 2 核的容器替**每个
 * 访客**把整张图（1~3MB）重下一遍；同时这些无用请求会占满浏览器对同域名仅有的 6 条
 * 并发连接，`<img>` 反而要排队——症状就是「画图页图片加载慢，右键新标签页打开却很快」。
 * 下载/加入参考都是用户主动点击，届时 fetchImageBlob 自己会取并缓存，无需预热。
 *
 * 保留在飞上限作为兜底：万一将来又被挂到批量路径上，最多只并行 2 个，不会雪崩。
 */
const MAX_INFLIGHT_WARMS = 2;
let inflightWarms = 0;

export function warmImageBlob(src: string) {
  if (!String(src || "").trim()) return;
  if (inflightWarms >= MAX_INFLIGHT_WARMS) return;
  inflightWarms += 1;
  void fetchImageBlob(src)
    .catch(() => undefined)
    .finally(() => {
      inflightWarms = Math.max(0, inflightWarms - 1);
    });
}

export function releaseImageBlob(src: string) {
  const key = normalizeImageUrl(src);
  const cached = imageBlobCache.get(key);
  if (!cached) return;
  imageBlobCache.delete(key);
  imageBlobCacheBytes = Math.max(0, imageBlobCacheBytes - cached.size);
}

export async function downloadImageSrc(src: string, filename: string) {
  const blob = await fetchImageBlob(src);
  const objectUrl = URL.createObjectURL(blob);
  const link = document.createElement("a");
  link.href = objectUrl;
  link.download = filename;
  document.body.appendChild(link);
  link.click();
  document.body.removeChild(link);
  URL.revokeObjectURL(objectUrl);
}