Function fetchFolderPeek

public/js/fileListView.js:3262–3352

* Best-effort peek: first few direct child folders + files for a folder. * Uses existing getFolderList.php + getFileList.php. * * Returns: { items: Array<{type,name}>, truncated: boolean }

(folder, sourceId = '')

 * Returns: { items: Array<{type,name}>, truncated: boolean }
 */
async function fetchFolderPeek(folder, sourceId = '') {
  if (!folder) return null;
  if (isSlowRemoteSource(sourceId)) return null;

  const key = folderCacheKey(folder, sourceId);
  if (_folderPeekCache.has(key)) {
    return _folderPeekCache.get(key);
  }

  const sourceParam = sourceId ? `&sourceId=${encodeURIComponent(sourceId)}` : '';
  const p = (async () => {
    try {
      // 1) Files in this folder
      let files = [];
      try {
        const res = await fetch(
          withBase(`/api/file/getFileList.php?folder=${encodeURIComponent(folder)}&recursive=0${sourceParam}&t=${Date.now()}`),
          { credentials: "include" }
        );
        const raw = await safeJson(res);
        if (Array.isArray(raw.files)) {
          files = raw.files;
        } else if (raw.files && typeof raw.files === "object") {
          files = Object.entries(raw.files).map(([name, meta]) => ({
            ...(meta || {}),
            name
          }));
        }
      } catch (e) {
        // ignore file errors; we can still show folders
      }

      // 2) Direct subfolders
      let subfolderNames = [];
      try {
        const res2 = await fetch(
          withBase(`/api/folder/getFolderList.php?folder=${encodeURIComponent(folder)}&counts=0${sourceParam}`),
          { credentials: "include" }
        );
        const raw2 = await safeJson(res2);

        if (Array.isArray(raw2)) {
          const allPaths = raw2.map(item => item.folder ?? item);
          const depth = folder === "root" ? 1 : folder.split("/").length + 1;

          subfolderNames = allPaths
            .filter(p => {
              if (folder === "root") return p.indexOf("/") === -1;
              if (!p.startsWith(folder + "/")) return false;
              return p.split("/").length === depth;
            })
            .map(p => p.split("/").pop() || p);
        }
      } catch (e) {
        // ignore folder errors
      }

      const items = [];