feat: export parser sessions from the browser

src/App.tsx

@@ -3,6 +3,10 @@ import { AppShell } from '@add-ideas/toolbox-shell-react';
 import '@add-ideas/toolbox-shell-react/styles.css';
 
 import { DiagnosticsPanel } from './components/DiagnosticsPanel.js';
+import {
+  ExportControls,
+  type OneNoteExportFormat,
+} from './components/ExportControls.js';
 import { FileDropZone } from './components/FileDropZone.js';
 import { HelpDialog } from './components/HelpDialog.js';
 import { PackageInspector } from './components/PackageInspector.js';
@@ -337,21 +341,39 @@ export function OneNoteApplication({
           suggestedName ??
           `onenote-resource.${resource.extension ?? 'bin'}`
       );
-      const url = URL.createObjectURL(
-        new Blob([resource.bytes], { type: resource.mediaType })
-      );
-      const anchor = document.createElement('a');
-      anchor.href = url;
-      anchor.download = filename;
-      anchor.rel = 'noopener';
-      document.body.append(anchor);
-      anchor.click();
-      anchor.remove();
-      window.setTimeout(() => URL.revokeObjectURL(url), 1_000);
+      downloadBrowserFile(resource.bytes, resource.mediaType, filename);
     },
     [loadSelectedResource]
   );
 
+  const exportLoadedSource = useCallback(
+    async (format: OneNoteExportFormat): Promise<void> => {
+      const client = activeClient.current;
+      if (!client || state.phase !== 'loaded') {
+        throw new WorkerClientError(
+          'session-not-available',
+          'The local parser session is no longer available.'
+        );
+      }
+      const response = await client.exportSession(
+        state.source.sessionId,
+        format
+      );
+      if (response.type === 'failure') {
+        throw new WorkerClientError(
+          response.error.code,
+          response.error.message
+        );
+      }
+      downloadBrowserFile(
+        response.artifact.bytes,
+        response.artifact.mediaType,
+        safeDownloadFilename(response.artifact.filename)
+      );
+    },
+    [state]
+  );
+
   const visibleDiagnostics = uniqueDiagnostics(
     (() => {
       if (state.phase !== 'loaded') return [];
@@ -409,6 +431,8 @@ export function OneNoteApplication({
             <PackageInspector notebook={state.source.notebook} />
           ) : null}
 
+          <ExportControls onExport={exportLoadedSource} />
+
           <div className="reader-workspace">
             {state.source.kind === 'one' ? (
               <SingleSectionNavigation
@@ -486,6 +510,22 @@ function safeDownloadFilename(value: string): string {
   return (cleaned || 'onenote-resource.bin').slice(0, 180);
 }
 
+function downloadBrowserFile(
+  bytes: ArrayBuffer,
+  mediaType: string,
+  filename: string
+): void {
+  const url = URL.createObjectURL(new Blob([bytes], { type: mediaType }));
+  const anchor = document.createElement('a');
+  anchor.href = url;
+  anchor.download = filename;
+  anchor.rel = 'noopener';
+  document.body.append(anchor);
+  anchor.click();
+  anchor.remove();
+  window.setTimeout(() => URL.revokeObjectURL(url), 1_000);
+}
+
 export function App() {
   const [helpOpen, setHelpOpen] = useState(false);