Add preview next previous navigation

server/public/app.js

@@ -120,7 +120,7 @@ function openProperties(entry = state.selectedEntry) {
   });
 }
 
-function openPreview(entry) {
+function openPreview(entry, sourceWindowId = state.focusedId) {
   if (!entry || !isPreviewable(entry)) {
     showError(new Error('Für diesen Dateityp ist keine Vorschau verfügbar.'));
     return null;
@@ -129,6 +129,7 @@ function openPreview(entry) {
   const existing = state.windows.find((item) => item.kind === 'preview');
   if (existing) {
     existing.data.entry = entry;
+    existing.data.sourceWindowId = sourceWindowId;
     existing.data.content = '';
     existing.data.loading = true;
     existing.data.error = null;
@@ -145,6 +146,7 @@ function openPreview(entry) {
     y: 110,
     data: {
       entry,
+      sourceWindowId,
       content: '',
       loading: true,
       error: null
@@ -333,7 +335,7 @@ function renderExplorer(body, win) {
       if (entry.type === 'directory') {
         loadExplorer(win, entry.path);
       } else if (isPreviewable(entry)) {
-        openPreview(entry);
+        openPreview(entry, win.id);
       }
     });
     row.addEventListener('contextmenu', (event) => {
@@ -425,13 +427,20 @@ function renderPreview(body, win) {
     return;
   }
   const entry = data.entry;
+  const navigation = previewNavigation(data);
   body.innerHTML = `
     <div class="preview-meta">
+      <div class="preview-nav">
+        <button class="icon" data-action="preview-prev" title="Vorherige Datei" aria-label="Vorherige Datei" ${navigation.previous ? '' : 'disabled'}>←</button>
+        <button class="icon" data-action="preview-next" title="Nächste Datei" aria-label="Nächste Datei" ${navigation.next ? '' : 'disabled'}>→</button>
+      </div>
       <strong>${escapeHtml(entry?.name || data.name || 'Vorschau')}</strong>
       <span>${escapeHtml(formatBytes(data.size || entry?.size || 0))}</span>
     </div>
     ${renderPreviewContent(data)}
   `;
+  body.querySelector('[data-action="preview-prev"]')?.addEventListener('click', () => openPreview(navigation.previous, data.sourceWindowId));
+  body.querySelector('[data-action="preview-next"]')?.addEventListener('click', () => openPreview(navigation.next, data.sourceWindowId));
 }
 
 function renderPreviewContent(data) {
@@ -456,6 +465,22 @@ function renderPreviewContent(data) {
   return `<pre class="preview-text">${escapeHtml(data.content || '')}</pre>`;
 }
 
+function previewNavigation(data) {
+  const source = state.windows.find((win) => win.id === data.sourceWindowId && win.kind === 'explorer');
+  const entries = (source?.data.entries || []).filter(isPreviewable);
+  if (entries.length < 2) {
+    return { previous: null, next: null };
+  }
+  const index = entries.findIndex((entry) => entry.path === data.entry?.path);
+  if (index < 0) {
+    return { previous: null, next: null };
+  }
+  return {
+    previous: entries[(index - 1 + entries.length) % entries.length],
+    next: entries[(index + 1) % entries.length]
+  };
+}
+
 async function loadPreview(win, entry) {
   win.data.loading = true;
   win.data.error = null;
@@ -463,6 +488,7 @@ async function loadPreview(win, entry) {
   try {
     const result = await api(apiUrl(`preview.php?path=${encodeURIComponent(entry.path)}`));
     win.data.entry = entry;
+    win.data.sourceWindowId = win.data.sourceWindowId || state.focusedId;
     win.data.name = result.name;
     win.data.size = result.size;
     win.data.type = result.type;
@@ -1000,7 +1026,7 @@ function renderContextMenu() {
     if (entry.type === 'directory') {
       actions.push(['Öffnen', () => loadExplorer(win, entry.path)]);
     } else if (isPreviewable(entry)) {
-      actions.push(['Vorschau', () => openPreview(entry)]);
+      actions.push(['Vorschau', () => openPreview(entry, win.id)]);
     }
     actions.push(['Eigenschaften', () => showPropertiesForEntry(win, entry)]);
     if (!isReadOnly()) {