/**
 * 懒加载 chunk / CSS preload 失败后的整页恢复。
 * 常见于：部署后旧 hash 失效、静态服务空闲断连、代理 CONNECTION_RESET。
 *
 * 失败后必须整页刷新：旧入口里的 hashed 资源地址不会自行更新，
 * 仅捕获路由错误而不刷新时，未打开过的页面会一直无法进入。
 */

const RELOAD_FLAG = 'app:chunk-reload-ts';
const RELOAD_QUERY = '_chunkreload';
const RELOAD_COOLDOWN_MS = 15000;

const CHUNK_ERROR_RE =
  /Failed to fetch dynamically imported module|Importing a module script failed|Unable to preload CSS|error loading dynamically imported module|Loading CSS chunk|Loading chunk .+ failed|ChunkLoadError|Unable to preload|error loading module|Load failed/i;

/** 最近一次路由跳转目标，供 onError 时整页落到正确地址 */
let pendingFullPath = '';
let installed = false;
let reloading = false;

export function setPendingRoutePath(fullPath = '') {
  pendingFullPath = fullPath || '';
}

function collectErrorText(error, depth = 0) {
  if (!error || depth > 3) return '';
  if (typeof error === 'string') return error;
  const parts = [
    error.message,
    error.msg,
    error.name,
    error.stack,
    error.error && collectErrorText(error.error, depth + 1),
    error.reason && collectErrorText(error.reason, depth + 1),
    error.cause && collectErrorText(error.cause, depth + 1),
    error.payload && collectErrorText(error.payload, depth + 1),
  ];
  const target = error.target;
  if (target && (target.src || target.href)) {
    parts.push(target.src || target.href);
  }
  try {
    parts.push(String(error));
  } catch (e) {
    /* ignore */
  }
  return parts.filter(Boolean).join(' ');
}

export function isChunkLoadError(error) {
  const text = collectErrorText(error);
  if (!text) return false;
  if (CHUNK_ERROR_RE.test(text)) return true;
  return /Failed to fetch/i.test(text) && /\.m?js(\?|$|:)/i.test(text);
}

export function hasReloadQuery(query = {}) {
  return !!(query && query[RELOAD_QUERY] !== undefined);
}

export function consumeReloadQuery(query = {}) {
  if (!hasReloadQuery(query)) return query;
  const next = { ...query };
  delete next[RELOAD_QUERY];
  return next;
}

function buildReloadUrl(targetPath) {
  const url = new URL(targetPath, window.location.origin);
  url.searchParams.set(RELOAD_QUERY, String(Date.now()));
  return url.pathname + url.search + url.hash;
}

/**
 * @returns {boolean} 是否已触发刷新（冷却期内返回 false，避免死循环）
 */
export function reloadForChunkError(targetPath) {
  if (reloading) return false;
  const now = Date.now();
  const last = Number(sessionStorage.getItem(RELOAD_FLAG) || 0);
  if (now - last < RELOAD_COOLDOWN_MS) {
    return false;
  }
  reloading = true;
  sessionStorage.setItem(RELOAD_FLAG, String(now));
  const path =
    targetPath ||
    pendingFullPath ||
    `${window.location.pathname}${window.location.search}${window.location.hash}`;
  const dest = buildReloadUrl(path);
  // cache: 'reload' 会回写 HTTP 缓存，降低 index.html 仍指向旧 hash 资源的概率
  fetch(`${window.location.pathname}?${RELOAD_QUERY}=${now}`, {
    cache: 'reload',
    credentials: 'same-origin',
    headers: {
      Pragma: 'no-cache',
      'Cache-Control': 'no-cache',
    },
  })
    .catch(() => {})
    .finally(() => {
      window.location.replace(dest);
    });
  return true;
}

export function wrapViewLoader(loader) {
  if (typeof loader !== 'function') return loader;
  return () =>
    Promise.resolve()
      .then(() => loader())
      .catch(error => {
        if (isChunkLoadError(error)) {
          reloadForChunkError();
        }
        throw error;
      });
}

export function installChunkReload() {
  if (installed || typeof window === 'undefined') return;
  installed = true;

  window.addEventListener('vite:preloadError', event => {
    if (reloadForChunkError()) {
      event.preventDefault();
    }
  });

  window.addEventListener('unhandledrejection', event => {
    if (!isChunkLoadError(event.reason)) return;
    if (reloadForChunkError()) {
      event.preventDefault();
    }
  });

  window.addEventListener(
    'error',
    event => {
      const el = event.target;
      const isAssetNode =
        el &&
        el !== window &&
        (el.tagName === 'SCRIPT' ||
          (el.tagName === 'LINK' && /modulepreload|stylesheet/i.test(el.rel || '')));
      if (isAssetNode || isChunkLoadError(event.error || event.message)) {
        if (reloadForChunkError()) {
          event.preventDefault();
        }
      }
    },
    true
  );

  document.addEventListener('visibilitychange', () => {
    if (document.visibilityState === 'visible') checkDeployedAssets();
  });
}

function checkDeployedAssets() {
  const el = document.querySelector('script[type="module"][src*="/assets/"]');
  if (!el || !el.src) return;
  fetch(el.src, { method: 'HEAD', cache: 'no-store', credentials: 'same-origin' })
    .then(res => {
      if (res.status === 404) reloadForChunkError();
    })
    .catch(() => {});
}