documents preview

server/src/index.ts

@@ -2,7 +2,7 @@ import crypto from 'node:crypto';
 import fs from 'node:fs';
 import path from 'node:path';
 import { fileURLToPath } from 'node:url';
-import { TextEncoder } from 'node:util';
+import { promisify, TextEncoder } from 'node:util';
 import { DatabaseSync } from 'node:sqlite';
 
 import cors from '@fastify/cors';
@@ -10,6 +10,7 @@ import jwt from '@fastify/jwt';
 import fastifyStatic from '@fastify/static';
 import websocket from '@fastify/websocket';
 import dotenv from 'dotenv';
+import libreOffice from 'libreoffice-convert';
 import {
   generateAuthenticationOptions,
   generateRegistrationOptions,
@@ -271,6 +272,12 @@ const webBundleFileParamsSchema = z.object({
   '*': z.string().min(1),
 });
 
+const officePreviewSchema = z.object({
+  fileName: z.string().trim().min(1).max(256),
+  mimeType: z.string().trim().min(1).max(256),
+  fileBase64: z.string().min(1).max(96_000_000),
+});
+
 const wsQuerySchema = z.object({
   token: z.string().min(1),
 });
@@ -346,6 +353,7 @@ const webAuthnUserVerification = resolveWebAuthnUserVerification(
 );
 const frontendIndexPath = path.join(frontendDistPath, 'index.html');
 const hasFrontendBuild = fs.existsSync(frontendIndexPath);
+const convertOfficeDocument = promisify(libreOffice.convertWithOptions);
 
 const speechTranscriber = new SpeechTranscriber(
   {
@@ -795,6 +803,41 @@ app.get('/api/auth/session', async (request, reply) => {
   };
 });
 
+app.post('/api/files/office-preview', { bodyLimit: 64 * 1024 * 1024 }, async (request, reply) => {
+  const authContext = await authenticateRequest(request, reply);
+
+  if (!authContext) {
+    return;
+  }
+
+  const parsed = officePreviewSchema.safeParse(request.body);
+
+  if (!parsed.success) {
+    return reply.code(400).send({
+      message: 'Invalid office preview payload.',
+      issues: parsed.error.flatten(),
+    });
+  }
+
+  if (!isSupportedOfficeDocument(parsed.data.fileName, parsed.data.mimeType)) {
+    return reply.code(400).send({ message: 'Only DOCX, XLSX, and PPTX files can be previewed.' });
+  }
+
+  try {
+    const pdfBuffer = await convertOfficeDocumentToPdf(parsed.data.fileName, parsed.data.fileBase64);
+
+    return {
+      mimeType: 'application/pdf',
+      pdfBase64: pdfBuffer.toString('base64'),
+    };
+  } catch (error) {
+    app.log.warn({ err: error, userId: authContext.user.id }, 'Office preview generation failed');
+    return reply.code(422).send({
+      message: describeOfficePreviewFailure(error),
+    });
+  }
+});
+
 app.get('/api/admin/pending-users', async (request, reply) => {
   const authContext = await authenticateRequest(request, reply);
 
@@ -1294,6 +1337,48 @@ async function authenticateTokenFromSession(
   };
 }
 
+async function convertOfficeDocumentToPdf(fileName: string, fileBase64: string): Promise<Buffer> {
+  const inputBuffer = Buffer.from(fileBase64, 'base64');
+
+  if (inputBuffer.byteLength === 0) {
+    throw new Error('The uploaded office document is empty.');
+  }
+
+  const normalizedFileName = normalizeOfficeDocumentFileName(fileName);
+  return convertOfficeDocument(inputBuffer, '.pdf', undefined, { fileName: normalizedFileName });
+}
+
+function isSupportedOfficeDocument(fileName: string, mimeType: string): boolean {
+  const normalizedFileName = fileName.trim().toLowerCase();
+  const normalizedMimeType = mimeType.trim().toLowerCase();
+
+  if (
+    normalizedMimeType === 'application/vnd.openxmlformats-officedocument.wordprocessingml.document'
+    || normalizedMimeType === 'application/vnd.openxmlformats-officedocument.spreadsheetml.sheet'
+    || normalizedMimeType === 'application/vnd.openxmlformats-officedocument.presentationml.presentation'
+  ) {
+    return true;
+  }
+
+  return /\.(docx|xlsx|xslx|pptx)$/i.test(normalizedFileName);
+}
+
+function normalizeOfficeDocumentFileName(fileName: string): string {
+  return fileName.trim().replace(/\.xslx$/i, '.xlsx');
+}
+
+function describeOfficePreviewFailure(error: unknown): string {
+  if (error && typeof error === 'object' && 'code' in error && error.code === 'ENOENT') {
+    return 'Office preview generation failed because LibreOffice is not installed on the server.';
+  }
+
+  if (error instanceof Error && error.message.trim()) {
+    return `Office preview generation failed: ${error.message}`;
+  }
+
+  return 'Office preview generation failed.';
+}
+
 function createUser(input: {
   username: string;
   displayName: string;