import {
  html, useState, useEffect, useRef, useCallback,
} from './vendor/htm-preact.js';
import { t } from './i18n.js';
import { Icon } from './icon.js';
import { entriesUnder } from './zipstream.js';
import { transfers } from './transfers.js';
import {
  FILE_ICONS, formatSize, formatDate, canPreview, CHUNK_SIZE, MEMORY_CEILING,
  pipelinedDownload, downloadEntry, downloadDirectory as sharedDownloadDirectory,
} from './file-utils.js';
import { useStickyBand } from './sticky.js';

// ── Files ────────────────────────────────────────────────────────────────────
//
// The group's file browser: toolbar (upload, mkdir, filter, select), the
// table itself, and every file/directory operation. `entries`/`nodeDirs`/
// `nodeRoots` are owned by the group shell (group-page.js) — Chat needs the
// same index for its image attachments — and handed down here read-only
// alongside `applyIndex`/the raw setters to write back through, the same
// shape ChatPanel already takes for `onRefreshIndex`.
//
// `onPreview` opens a file in the shell's video/preview modal rather than
// this component owning that state itself, again because more than one tab
// (Chat's attachments) can trigger it.

function FilesPanel({
  groupId, transportRef, gekRef, status,
  entries, nodeDirs, nodeRoots, setEntries, setNodeDirs, setNodeRoots, applyIndex,
  isNodeAdmin, operatorPaired, userId, setError, onPreview,
  showGroup, readOnly, getTransport, onRefreshIndex, showRefresh,
}) {
  const [selected, setSelected] = useState(() => new Set());
  const [sortKey, setSortKey] = useState('name');
  const [sortAsc, setSortAsc] = useState(true);
  const [filter, setFilter] = useState('');
  const [currentPath, setCurrentPath] = useState('');
  const [refreshing, setRefreshing] = useState(false);
  // The toolbar pins below the page's own band and tells the column heads how
  // far down to pin. Its height is not a constant — it wraps to three rows on
  // a phone and grows a field while a folder is being named — so it is
  // measured rather than written down (sticky.js).
  const toolbarBand = useStickyBand('--toolbar-h');

  // Only the cross-group Search page shows this (`showRefresh`): it has no
  // live node connection pushing index deltas, so its file list really is
  // a one-shot cached fetch. In a real group the node streams every change
  // as it happens, so a manual re-fetch would just duplicate that.
  const doRefresh = useCallback(async () => {
    if (refreshing || !onRefreshIndex) return;
    setRefreshing(true);
    try { await onRefreshIndex(); } finally { setRefreshing(false); }
  }, [refreshing, onRefreshIndex]);

  // A directory from the group just left rarely exists in the one just
  // entered (e.g. "outputs" in one group, absent in another) — Files would
  // otherwise show that stale path and list nothing.
  useEffect(() => { setCurrentPath(''); setSelected(new Set()); setFilter(''); }, [groupId]);

  const downloadFile = useCallback(async (entry) => {
    let transport, gek;
    if (getTransport) {
      try {
        const conn = await getTransport(entry);
        transport = conn.transport;
        gek = conn.gek;
      } catch {
        setError(t('search.unreachable', { n: 1 }));
        return;
      }
    } else {
      transport = transportRef.current;
      gek = gekRef.current;
    }
    // Never a silent return. A click that produces nothing at all — no
    // transfer, no icon, no message — is indistinguishable from a broken
    // button, and it is what a download looks like whenever the WebRTC
    // connection is not up: on a screen lock, mid-reconnect, or after the node
    // restarted. Say so instead.
    if (!transport || !transport.connected) {
      setError(t('group.download_offline'));
      return;
    }
    await downloadEntry(transfers, transport, gek, entry);
  }, [getTransport]);

  const uploadFile = useCallback((e) => {
    const files = [...(e.target.files || [])];
    e.target.value = '';
    const transport = transportRef.current;
    if (!files.length || !transport || !transport.connected) return;
    // The folder on screen is the destination — not its root, and not a
    // subdirectory of the node's invention. Somebody dropping a file into the
    // folder they are looking at expects it to be in that folder.
    const uploadDir = currentPath;
    if (!uploadDir) return;
    const uploadRoot = uploadDir.split('/')[0];
    setError('');

    for (const file of files) {
      transfers.start({
        kind: 'upload', name: file.name, total: file.size, transport,
        // `makeLease`, not `lease`: pausing gives the slot back, so resuming
        // has to be able to ask for another one, and a transfer handed a lease
        // it cannot re-create is refused the button rather than offered one
        // that would drop its slot for good.
        makeLease: () => transport.openTransfer({ kind: 'upload',
                                                  bytes: file.size }),
        // A `File` is seekable and the node remembers how much it holds, so
        // there is no target tier to consult here — unlike a download.
        pausable: true,
        run: async ({ signal, onProgress, lease }) => {
          await transport.uploadFile(file, {
            // Bytes the node acknowledged, not bytes read locally.
            onProgress: (sent) => onProgress(sent, file.size),
            signal,
            root: uploadRoot,
            dir: uploadDir,
            tr: lease && lease.tr,
          });
          // The node re-indexes on a filesystem event, so there is nothing to
          // wait on but the clock. Refreshing here means the file appears in
          // the list without anyone reloading.
          await new Promise(r => setTimeout(r, 2500));
          if (transport.connected) applyIndex(await transport.fetchIndex());
        },
      });
    }
  }, [applyIndex, currentPath]);

  // `null` while not creating one; a draft string while the field is open.
  const [newDirName, setNewDirName] = useState(null);
  const [creatingDir, setCreatingDir] = useState(false);

  /**
   * Create a folder in the directory being browsed.
   *
   * The name comes from a field in the toolbar rather than `window.prompt`,
   * which **throws** in Electron — "prompt() is not supported" — and threw
   * outside this function's try, so clicking the button did nothing at all:
   * no folder, no error, nothing in the interface to react to. `confirm()` and
   * `alert()` do work there and are used elsewhere; `prompt` is the one
   * Chromium leaves to the embedder and Electron declines to implement.
   *
   * An inline field is better anyway — it can show the refusal next to the
   * input instead of after the dialog has closed.
   */
  useEffect(() => { setNewDirName(null); }, [currentPath]);

  const makeDirectory = useCallback(async (rawName) => {
    const transport = transportRef.current;
    const name = (rawName || '').trim();
    if (!name) return;
    if (!transport || !transport.connected) {
      setError(t('group.mkdir_offline'));
      return;
    }
    setCreatingDir(true);
    try {
      await transport.createDirectory(currentPath, name);
      // `list_dirs` walks the filesystem rather than the index, so a folder
      // with nothing in it is here on this very fetch.
      const indexMsg = await transport.fetchIndex();
      if (indexMsg.entries) setEntries(indexMsg.entries);
      if (indexMsg.dirs) setNodeDirs(indexMsg.dirs);
      if (indexMsg.roots) setNodeRoots(indexMsg.roots);
      setNewDirName(null);
    } catch (err) {
      setError(err.message);
    } finally {
      setCreatingDir(false);
    }
  }, [currentPath]);

  // The implementation lives in file-utils.js (docs/photos.md §3) so
  // photos-app.js's own "zip this album" button can call the same code
  // rather than a second one.
  const downloadDirectory = useCallback(async (dir) => {
    const transport = transportRef.current;
    await sharedDownloadDirectory(
      transfers, transport, gekRef.current, entries, dir, { setError });
  }, [entries]);

  const deleteDirectory = useCallback(async (dir) => {
    const transport = transportRef.current;
    if (!transport || !transport.connected) return;
    try {
      const sk = transport.sessionKeys && transport.sessionKeys.skEdB64;
      const signFn = (sk && window.MeshBayKeys)
        ? (transcript) => window.MeshBayKeys.signBytes(sk, transcript)
        : null;
      await transport.deleteDirectory(dir, signFn);
      applyIndex(await transport.fetchIndex());
    } catch (err) {
      setError(err.message);
    }
  }, [applyIndex]);

  const deleteFile = useCallback(async (entry) => {
    const transport = transportRef.current;
    if (!transport || !transport.connected) return;
    try {
      // Signs an explicit transcript built by transport.js, not opaque bytes from
      // the node — see MeshBayCrypto.adminTranscript and finding H5.
      // Signed with the identity this node pinned for us — the only one it
      // will accept, and the only one we hold here.
      const sk = transport.sessionKeys && transport.sessionKeys.skEdB64;
      const signFn = (sk && window.MeshBayKeys)
        ? (transcript) => window.MeshBayKeys.signBytes(sk, transcript)
        : null;
      await transport.deleteFile(entry.id, signFn);
      applyIndex(await transport.fetchIndex());
    } catch (err) {
      setError(err.message);
    }
  }, [applyIndex]);

  const toggleSort = useCallback((key) => {
    setSortAsc(prev => sortKey === key ? !prev : true);
    setSortKey(key);
  }, [sortKey]);

  // With text in the field the user is searching, not browsing: match every
  // file in the whole group, wherever it lives, by name or by the folder it
  // sits in — and hide the folder rows, there is nothing to walk into. The
  // old code only ever filtered files whose folder was exactly `currentPath`,
  // so at the top of a group — where the rows are roots, never loose files —
  // typing did nothing at all.
  const q = filter.trim().toLowerCase();
  const dirs = new Set();
  const filteredEntries = entries.filter(e => {
    const ePath = e.path || '';
    if (q) {
      return (e.name || '').toLowerCase().includes(q)
          || ePath.toLowerCase().includes(q);
    }
    if (ePath === currentPath) return true;
    if (!currentPath && ePath) {
      dirs.add(ePath.split('/')[0]);
    } else if (currentPath && ePath.startsWith(currentPath + '/')) {
      const rest = ePath.slice(currentPath.length + 1);
      dirs.add(rest.split('/')[0]);
    }
    return false;
  });

  const sorted = [...filteredEntries].sort((a, b) => {
    let cmp = 0;
    if (sortKey === 'name') cmp = (a.name || '').localeCompare(b.name || '');
    else if (sortKey === 'size') cmp = a.size - b.size;
    else if (sortKey === 'type') cmp = (a.type || '').localeCompare(b.type || '');
    else if (sortKey === 'date') cmp = a.added_at - b.added_at;
    return sortAsc ? cmp : -cmp;
  });

  // The node's own listing, so an empty folder is visible, plus anything implied
  // by a file path in case the two ever disagree. Skipped while searching — the
  // results are a flat list of matches, not a folder view.
  if (!q) for (const d of nodeDirs) {
    if (!currentPath && !d.includes('/')) dirs.add(d);
    else if (currentPath && d.startsWith(currentPath + '/')) {
      const rest = d.slice(currentPath.length + 1);
      if (!rest.includes('/')) dirs.add(rest);
    }
  }
  const subdirs = [...dirs].sort();

  // At the top of a group the folders on screen ARE the roots, so their state
  // belongs there. Deeper in, everything shown lives inside one readable root
  // and there is nothing to flag.
  const rootState = new Map(nodeRoots.map(r => [r.name, r]));
  const unavailableHere = currentPath
    ? []
    : subdirs.filter(d => rootState.get(d) && rootState.get(d).available === false);
  const currentRootName = currentPath ? currentPath.split('/')[0] : '';
  const currentRoot = currentRootName ? rootState.get(currentRootName) : null;
  const currentRootWritable = currentRoot ? Boolean(currentRoot.writable)
                                          : false;
  // A member cannot create a folder at the top of a group: that level is the
  // set of roots, which is the operator's configuration and not a directory on
  // anyone's disk. The node refuses it, so offering it would only produce an
  // error nobody can act on.
  //
  // Otherwise the rule is the same as the Upload button's, and for the same
  // reason the node gives: "making a directory is not a privileged act — a
  // member who can add a file can organise where it goes". It used to require
  // `isNodeAdmin`, which contradicted the node and hid the control from
  // everyone who could actually use it.
  const canCreateDir = Boolean(currentPath) && currentRootWritable && !readOnly;

  const breadcrumbs = currentPath ? currentPath.split('/') : [];

  // Selection is keyed globally — file ids, and 'dir:' plus a full path — so
  // walking into another folder keeps what was already ticked.
  const dirKey = (name) => 'dir:' + (currentPath ? currentPath + '/' + name : name);
  const selectedFiles = entries.filter(e => selected.has(e.id));
  const selectedDirs = [...selected]
    .filter(k => typeof k === 'string' && k.startsWith('dir:'))
    .map(k => k.slice(4));
  const toggle = (key) => setSelected(prev => {
    const next = new Set(prev);
    if (next.has(key)) next.delete(key); else next.add(key);
    return next;
  });

  const allVisibleKeys = [...subdirs.map(d => dirKey(d)), ...sorted.map(e => e.id)];
  const allSelected = allVisibleKeys.length > 0 && allVisibleKeys.every(k => selected.has(k));
  const someSelected = allVisibleKeys.some(k => selected.has(k));
  const toggleAll = () => {
    if (allSelected) {
      setSelected(new Set());
    } else {
      setSelected(prev => {
        const next = new Set(prev);
        for (const k of allVisibleKeys) next.add(k);
        return next;
      });
    }
  };

  const onlyFile = selectedFiles.length === 1 && selectedDirs.length === 0
    ? selectedFiles[0] : null;
  const deletableFiles = selectedFiles.filter(
    e => isNodeAdmin || (userId && e.uploader_id === userId));

  const run = (fn) => {
    setSelected(new Set());
    Promise.resolve().then(fn).catch(err => {
      if (err && err.name !== 'AbortError') setError(err.message);
    });
  };

  // Icon only, with the name in the tooltip: these sit in a toolbar that is
  // already narrow, and every one of them is a verb the icon carries on its
  // own. `title` gives the hover text and `aria-label` the accessible name —
  // an icon button with neither is unusable with a screen reader.
  //
  // Every action is rendered as soon as Select is on, and the ones that do not
  // apply are disabled rather than absent. Buttons appearing and vanishing as
  // the selection changed made the bar jump about and gave no clue that an
  // action existed at all before something was ticked.
  const action = (icon, label, onClick, opts = {}) => html`
    <button class="tb-icon-btn ${opts.danger ? 'danger' : ''}"
      title=${label} aria-label=${label}
      disabled=${!!opts.disabled} onClick=${onClick}>
      <${Icon} name=${icon} />
    </button>
  `;

  const canPlay = !!(onlyFile && (onlyFile.type === 'video' || onlyFile.type === 'audio'));
  const canView = !!(onlyFile && onlyFile.type !== 'video' && onlyFile.type !== 'audio'
    && canPreview(onlyFile));
  const deletableCount = deletableFiles.length
    + (operatorPaired ? selectedDirs.length : 0);
  // The operator can always delete; anyone else only ever sees the button if
  // something here is theirs to remove. Hiding it from an uploader would take
  // away a right the protocol grants them (draft-v5 §5.1), not just a control.
  const mayEverDelete = isNodeAdmin
    || (userId && entries.some(e => e.uploader_id === userId));

  const actionItems = html`
    ${action('play', t('group.play'),
      () => run(() => onPreview(onlyFile)), { disabled: !canPlay })}
    ${action('eye', t('group.view'),
      () => run(() => onPreview(onlyFile)), { disabled: !canView })}
    ${action('download',
      selectedFiles.length
        ? t('group.download_n', { n: selectedFiles.length })
        : t('group.download'),
      () => run(async () => {
        // Awaited one at a time, and each returns as soon as its transfer is
        // registered — so the transfers still run together. Firing them without
        // awaiting meant every file asked the browser for a save dialog at
        // once, and a browser allows one: the rest were rejected and only the
        // first file ever downloaded.
        for (const e of selectedFiles) await downloadFile(e);
      }), { disabled: selectedFiles.length === 0 })}
    ${!readOnly && action('archive',
      selectedDirs.length
        ? t('group.download_zip_n', { n: selectedDirs.length })
        : t('group.download_zip_n', { n: 0 }),
      () => run(async () => {
        for (const d of selectedDirs) await downloadDirectory(d);
      }), { disabled: selectedDirs.length === 0 })}
    ${mayEverDelete && !readOnly && action('trash',
      deletableCount ? t('group.delete_n', { n: deletableCount }) : t('group.delete'),
      () => {
        const names = [...deletableFiles.map(e => e.name),
                       ...(operatorPaired ? selectedDirs : [])];
        if (!confirm(t('group.delete_n_confirm', { n: names.length,
                                                   names: names.join(', ') }))) return;
        run(() => {
          for (const e of deletableFiles) deleteFile(e);
          if (operatorPaired) for (const d of selectedDirs) deleteDirectory(d);
        });
      },
      { danger: true, disabled: status !== 'connected' || deletableCount === 0 })}
  `;

  return html`
    ${(status === 'discovering' || status === 'connecting' || status === 'fetching') && html`
      <p class="page-message"><span class="spinner"></span>${' '}${t('status.connecting_short')}</p>
    `}
    ${status === 'offline' && html`
      <p class="page-message">${t('group.offline_title')} ${t('group.offline_hint')}</p>
    `}

    ${status === 'connected' && html`
      <div class="file-toolbar" ref=${toolbarBand}>
        <div class="toolbar-group">
          ${currentPath && currentRootWritable && html`
          <label class="tb-btn primary">
            <${Icon} name="upload" /> ${t('group.upload')}
            <input type="file" multiple style="display:none"
              onChange=${uploadFile} />
          </label>
          `}
          ${/* Icon only: the toolbar already carries a labelled primary
                action, and a second one beside it competes with it for the
                width a breadcrumb trail needs. The name lives in the tooltip
                and in aria-label, so it is not lost to anyone reading with
                something other than their eyes. */''}
          ${canCreateDir && newDirName === null && html`
          <button class="tb-btn tb-btn-icon" onClick=${() => setNewDirName('')}
            title=${t('group.mkdir')} aria-label=${t('group.mkdir')}>
            <${Icon} name="folder-plus" />
          </button>
          `}
          ${canCreateDir && newDirName !== null && html`
          <span class="tb-mkdir">
            <input type="text" class="tb-mkdir-input" autofocus
              value=${newDirName} disabled=${creatingDir}
              placeholder=${t('group.mkdir_prompt')}
              aria-label=${t('group.mkdir')}
              onInput=${(e) => setNewDirName(e.target.value)}
              onKeyDown=${(e) => {
                if (e.key === 'Enter') makeDirectory(newDirName);
                if (e.key === 'Escape') setNewDirName(null);
              }} />
            <button class="tb-btn tb-btn-icon" title=${t('group.mkdir')}
              disabled=${creatingDir || !newDirName.trim()}
              onClick=${() => makeDirectory(newDirName)}>
              <${Icon} name="check" />
            </button>
            <button class="tb-btn tb-btn-icon" title=${t('settings.cancel')}
              disabled=${creatingDir}
              onClick=${() => setNewDirName(null)}>
              <${Icon} name="close" />
            </button>
          </span>
          `}
        </div>

        <div class="breadcrumbs">
          ${showRefresh && onRefreshIndex && html`
            <button class="crumb crumb-refresh ${refreshing ? 'spinning' : ''}"
              onClick=${doRefresh} disabled=${refreshing}
              title=${t('group.refresh_index')}>
              <${Icon} name="refresh" />
            </button>
          `}
          <a class="crumb" onClick=${() => setCurrentPath('')}>
            <${Icon} name="home" />
          </a>
          ${breadcrumbs.map((seg, i) => {
            const path = breadcrumbs.slice(0, i + 1).join('/');
            return html`
              <span class="crumb-sep">/</span>
              <a class="crumb" onClick=${() => setCurrentPath(path)}>${seg}</a>
            `;
          })}
        </div>

        <div class="toolbar-group right">
          ${!readOnly && html`<div class="tb-search">
            <${Icon} name="search" />
            <input type="text" placeholder="${t('group.filter')}"
              value=${filter} onInput=${e => setFilter(e.target.value)} />
          </div>`}
          <div class="tb-actions">${actionItems}</div>
        </div>
      </div>
      <table class="file-table">
        <thead>
          <tr>
            <th class="sel-cell">
              <input type="checkbox" checked=${allSelected}
                ref=${(el) => { if (el) el.indeterminate = someSelected && !allSelected; }}
                onChange=${toggleAll} />
            </th>
            <th></th>
            <th class="sortable" onClick=${() => toggleSort('name')}>
              ${t('group.col_name')} ${sortKey === 'name' ? (sortAsc ? '▲' : '▼') : ''}
            </th>
            <th class="sortable" onClick=${() => toggleSort('size')}>
              ${t('group.col_size')} ${sortKey === 'size' ? (sortAsc ? '▲' : '▼') : ''}
            </th>
            ${showGroup && html`<th class="td-group">${t('search.col_group')}</th>`}
            <th class="sortable th-type" onClick=${() => toggleSort('type')}>
              ${t('group.col_type')} ${sortKey === 'type' ? (sortAsc ? '▲' : '▼') : ''}
            </th>
            <th class="sortable th-date" onClick=${() => toggleSort('date')}>
              ${t('group.col_date')} ${sortKey === 'date' ? (sortAsc ? '▲' : '▼') : ''}
            </th>
          </tr>
        </thead>
        <tbody>
          ${currentPath && html`
            <tr class="file-row dir-row" key="__parent__" onClick=${() => {
              const parts = currentPath.split('/');
              setCurrentPath(parts.slice(0, -1).join('/'));
            }}>
              <td class="sel-cell"></td>
              <td>${'\u{1F4C1}'}</td>
              <td>..</td>
              <td class="file-size"></td>
              ${showGroup && html`<td class="td-group"></td>`}
              <td class="td-type"></td>
              <td class="td-date"></td>
            </tr>
          `}
          ${subdirs.map(d => {
            const full = currentPath ? currentPath + '/' + d : d;
            const inside = entriesUnder(entries, full);
            const bytes = inside.reduce((n, f) => n + (f.entry.size || 0), 0);
            const rs = rootState.get(d);
            const isEjected = rs && rs.ejected;
            const isUnavail = unavailableHere.includes(d);
            const isRemovable = rs && rs.removable;
            return html`
            <tr class="file-row dir-row${isEjected ? ' root-ejected' : ''}" key=${full}
                onClick=${() => { if (!isEjected) setCurrentPath(full); }}>
                <td class="sel-cell">
                  <input type="checkbox" checked=${selected.has(dirKey(d))}
                    onClick=${(ev) => ev.stopPropagation()}
                    onChange=${() => toggle(dirKey(d))} />
                </td>
              <td>${isEjected ? '\u{23CF}' : isUnavail ? '\u{26A0}' : '\u{1F4C1}'}</td>
              ${/* `file-name`, like a file's own name cell. Without it this
                    was a bare <td>, so a folder called
                    `Rage_Against_The_Machine_Discography_1992-2000_FLAC` —
                    one unbreakable word, which is how music libraries are
                    named — set the column's minimum width to the whole
                    string. Measured on a phone: a 527px table in a 390px
                    window, and on Android a page wider than the screen takes
                    every pinned header out of the visible area with it. */''}
              <td class="file-name">${d}${isEjected ? html`
                <span class="root-offline"> ${t('group.root_ejected')}</span>
              ` : isUnavail ? html`
                <span class="root-offline"> ${t('group.root_unavailable')}</span>
              ` : ''}${rs && rs.writable && !isEjected ? html`
                <span class="root-rw" title="${t('group.root_writable')}" style="margin-left:8px;opacity:0.5;font-size:0.9em">✎</span>
              ` : ''}${isRemovable && isNodeAdmin && operatorPaired ? html`
                <button class="btn-small root-eject-btn" title=${isEjected ? t('group.root_plug') : t('group.root_eject')}
                  onClick=${(ev) => {
                  ev.stopPropagation();
                  const transport = transportRef.current;
                  if (!transport) return;
                  const sk = transport.sessionKeys && transport.sessionKeys.skEdB64;
                  const signFn = (sk && window.MeshBayKeys)
                    ? (transcript) => window.MeshBayKeys.signBytes(sk, transcript)
                    : null;
                  const fn = isEjected
                    ? () => transport.plugRoot(groupId, d, signFn)
                    : () => transport.ejectRoot(groupId, d, signFn);
                  fn().catch((err) => setError(err.message));
                }}>${isEjected ? '\u{1F50C}' : '\u{23CF}'}</button>
              ` : ''}</td>
              <td class="file-size">${inside.length ? formatSize(bytes) : ''}</td>
              ${showGroup && html`<td class="td-group"></td>`}
              <td class="td-type"></td>
              <td class="td-date"></td>
            </tr>
          `; })}
          ${sorted.map(e => html`
              <tr class="file-row" key=${e.id}>
                <td class="sel-cell">
                  <input type="checkbox" checked=${selected.has(e.id)}
                    onClick=${(ev) => ev.stopPropagation()}
                    onChange=${() => toggle(e.id)} />
                </td>
                <td>${FILE_ICONS[e.type] || FILE_ICONS.other}</td>
                <td class="file-name">
                  ${canPreview(e)
                    ? html`<a class="file-link" onClick=${() => onPreview(e)}>${e.name}</a>`
                    : e.name
                  }
                  ${q && e.path && html`
                    <a class="file-loc"
                       onClick=${() => { setFilter(''); setCurrentPath(e.path); }}>${e.path}</a>`}
                </td>
                <td class="file-size">${formatSize(e.size)}</td>
                ${showGroup && html`<td class="td-group">
                  <a href="#/group/${e.groupId}" class="badge">${e.groupName || ''}</a>
                </td>`}
                <td class="file-type td-type">${e.type}</td>
                <td class="file-date td-date">${formatDate(e.added_at)}</td>
              </tr>
            `)}
          ${sorted.length === 0 && subdirs.length === 0 && html`
            <tr><td colspan=${6 + (showGroup ? 1 : 0)} class="file-empty">
              ${filter ? t('group.empty_filter') : t('group.empty_dir')}
            </td></tr>
          `}
        </tbody>
      </table>
    `}
  `;
}

// ── File Preview (text, images) ─────────────────────────────────────────

const TEXT_EXTS = /\.(txt|md|json|csv|log|xml|yaml|yml|ini|conf|py|js|html|css|sh|c|h|java|rs|go|rb|toml)$/i;
const IMAGE_EXTS = /\.(jpg|jpeg|png|gif|webp|svg|bmp|ico)$/i;

function FilePreview({ entry, transportRef, gekRef, onClose, onDownload }) {
  const [phase, setPhase] = useState('loading');
  const [progress, setProgress] = useState(0);
  const [content, setContent] = useState(null);
  const [error, setError] = useState('');
  const [downloading, setDownloading] = useState(false);
  const blobUrlRef = useRef(null);

  useEffect(() => {
    let cancelled = false;
    const load = async () => {
      // Nothing here streams: a preview is decrypted whole, held as an array of
      // chunks, and turned into a blob. That is right for a page of text and a
      // photograph, and it is a dead tab for the things that also reach here —
      // a scanned PDF, a multi-gigabyte .csv or .log. There was no size test at
      // all, and the text branch is the sharpest illustration: it decoded the
      // entire file and then kept 500 000 characters of it.
      //
      // Films and music never arrive (group-page.js's onPreview routes video to
      // the MSE player and audio to the music queue), so this guard is only ever
      // met by a document somebody clicked without knowing how big it was. It
      // offers the download instead, which does stream.
      if (entry.size > MEMORY_CEILING) {
        setError(t('preview.too_large', {
          size: formatSize(entry.size), limit: formatSize(MEMORY_CEILING),
        }));
        setPhase('error');
        return;
      }
      const transport = transportRef.current;
      if (!transport || !transport.connected) {
        setError(t('video.err_transport'));
        setPhase('error');
        return;
      }
      try {
        const totalChunks = Math.ceil(entry.size / CHUNK_SIZE);
        let downloaded = 0;
        const chunks = await pipelinedDownload(
          transport, gekRef.current, entry.id, totalChunks,
          (bytes) => { downloaded += bytes; setProgress(downloaded / entry.size); },
        );
        if (cancelled) return;

        if (/\.pdf$/i.test(entry.name)) {
          // Decrypted here and shown from a blob: URL — the bytes never leave
          // the page, and the browser's own viewer renders them.
          const blob = new Blob(chunks, { type: 'application/pdf' });
          blobUrlRef.current = URL.createObjectURL(blob);
          setContent({ type: 'pdf' });
        } else if (entry.name.match(IMAGE_EXTS)) {
          const ext = entry.name.split('.').pop().toLowerCase();
          const mime = ext === 'svg' ? 'image/svg+xml'
            : ext === 'png' ? 'image/png'
            : ext === 'gif' ? 'image/gif'
            : ext === 'webp' ? 'image/webp'
            : 'image/jpeg';
          const blob = new Blob(chunks, { type: mime });
          blobUrlRef.current = URL.createObjectURL(blob);
          setContent({ type: 'image' });
        } else {
          const decoder = new TextDecoder('utf-8', { fatal: false });
          const text = chunks.map(c => decoder.decode(c, { stream: true })).join('');
          setContent({ type: 'text', text: text.slice(0, 500000) });
        }
        setPhase('ready');
      } catch (err) {
        if (!cancelled) { setError(err.message); setPhase('error'); }
      }
    };
    load();
    return () => { cancelled = true; };
  }, [entry]);

  useEffect(() => {
    const onKey = (e) => { if (e.key === 'Escape') onClose(); };
    window.addEventListener('keydown', onKey);
    return () => window.removeEventListener('keydown', onKey);
  }, [onClose]);

  useEffect(() => {
    return () => {
      if (blobUrlRef.current) {
        URL.revokeObjectURL(blobUrlRef.current);
        blobUrlRef.current = null;
      }
    };
  }, []);

  return html`
    <div class="video-overlay" onClick=${(e) => {
      if (e.target.classList.contains('video-overlay')) onClose();
    }}>
      <div class="video-top-bar">
        <span class="video-title">${entry.name} (${formatSize(entry.size)})</span>
        ${onDownload && html`
          <button class="video-close ${downloading ? 'dl-active' : ''}"
            onClick=${() => {
              if (!downloading) {
                setDownloading(true);
                onDownload();
                setTimeout(() => setDownloading(false), 1500);
              }
            }}
            title="${t('group.download')}" disabled=${downloading}>
            ${downloading
              ? html`<span class="spinner"></span>`
              : html`<${Icon} name="download" />`}</button>
        `}
        <button class="video-close" onClick=${onClose} title="${t('video.close')}">
          <${Icon} name="close" /></button>
      </div>
      ${phase === 'loading' && html`
        <div class="video-loading">
          <div class="video-loading-label">${t('video.loading', { name: entry.name })}</div>
          <div class="video-progress-bar">
            <div class="video-progress-fill" style="width:${Math.round(progress * 100)}%"></div>
          </div>
        </div>
      `}
      ${phase === 'ready' && content?.type === 'pdf' && html`
        <object data=${blobUrlRef.current} type="application/pdf"
                class="preview-pdf" aria-label=${entry.name}>
          <p class="page-message">${t('preview.pdf_fallback')}</p>
        </object>
      `}
      ${phase === 'ready' && content?.type === 'image' && html`
        <div class="preview-image-wrap">
          <img class="preview-image" src=${blobUrlRef.current} alt=${entry.name} />
        </div>
      `}
      ${phase === 'ready' && content?.type === 'text' && html`
        <div class="preview-text-wrap">
          <pre class="preview-text">${content.text}</pre>
        </div>
      `}
      ${phase === 'error' && html`
        <div class="video-error">${error}</div>
      `}
    </div>
  `;
}

export { FilesPanel, FilePreview };