From fd39cab8458fd442831051b5d816be554f5ac2e4 Mon Sep 17 00:00:00 2001
From: Carlos Valente <carlosvalente@pm.me>
Date: Sun, 15 Mar 2026 20:58:08 +0100
Subject: [PATCH] fix: prevent sheet name too long in excel export

---
 .../excel/__tests__/excel.service.test.ts     | 37 +++++++++++++++++++
 .../src/api-data/excel/excel.service.ts       | 15 +++++++-
 2 files changed, 51 insertions(+), 1 deletion(-)
 create mode 100644 apps/server/src/api-data/excel/__tests__/excel.service.test.ts

diff --git a/apps/server/src/api-data/excel/__tests__/excel.service.test.ts b/apps/server/src/api-data/excel/__tests__/excel.service.test.ts
new file mode 100644
index 000000000..b8e0e18fc
--- /dev/null
+++ b/apps/server/src/api-data/excel/__tests__/excel.service.test.ts
@@ -0,0 +1,37 @@
+import xlsx from 'xlsx';
+
+import { demoDb } from '../../../models/demoProject.js';
+import { generateExcelFile } from '../excel.service.js';
+
+describe('generateExcelFile()', () => {
+  it('sanitises long worksheet names to an Excel-compatible value', () => {
+    const buffer = generateExcelFile(
+      {
+        ...demoDb.rundowns.default,
+        title: 'This is a very long name with many characters and weird things: like [Main]/?*',
+      },
+      demoDb.customFields,
+    );
+
+    const workbook = xlsx.read(buffer, { type: 'buffer' });
+    const worksheetName = workbook.SheetNames[0];
+
+    expect(worksheetName).toBeDefined();
+    expect(worksheetName.length).toBeLessThanOrEqual(31);
+    expect(worksheetName).not.toMatch(/[:\\/?*3[\]]/);
+  });
+
+  it('falls back to default worksheet name when title is fully invalid', () => {
+    const buffer = generateExcelFile(
+      {
+        ...demoDb.rundowns.default,
+        title: '[]:*?/\\',
+      },
+      demoDb.customFields,
+    );
+
+    const workbook = xlsx.read(buffer, { type: 'buffer' });
+
+    expect(workbook.SheetNames[0]).toBe('Rundown');
+  });
+});
diff --git a/apps/server/src/api-data/excel/excel.service.ts b/apps/server/src/api-data/excel/excel.service.ts
index b0085a150..4333c738e 100644
--- a/apps/server/src/api-data/excel/excel.service.ts
+++ b/apps/server/src/api-data/excel/excel.service.ts
@@ -21,6 +21,18 @@ import { rundownToTabular } from './excel.utils.js';
 // we keep the excel data in memory to allow the flow upload -> preview
 let excelData: WorkBook = xlsx.utils.book_new();
 
+const maxWorksheetNameLength = 31;
+const invalidWorksheetCharsRegex = /[:\\/?*[\]]/g;
+
+function getValidWorksheetName(title: string): string {
+  const sanitisedTitle = title.replaceAll(invalidWorksheetCharsRegex, ' ').trim().replace(/\s+/g, ' ');
+
+  const withFallback = sanitisedTitle.length > 0 ? sanitisedTitle : 'Rundown';
+  const truncatedTitle = withFallback.slice(0, maxWorksheetNameLength).trim();
+
+  return truncatedTitle.length > 0 ? truncatedTitle : 'Rundown';
+}
+
 /**
  * Receives and parses an excel file
  * The file is deleted after being read
@@ -93,7 +105,8 @@ export function generateExcelFile(rundown: Rundown, customFields: CustomFields):
 
   const workbook = xlsx.utils.book_new();
   const worksheet = xlsx.utils.aoa_to_sheet(rundownToTabular(rundown, customFields));
-  xlsx.utils.book_append_sheet(workbook, worksheet, rundown.title || 'Rundown');
+  const worksheetName = getValidWorksheetName(rundown.title || 'Rundown');
+  xlsx.utils.book_append_sheet(workbook, worksheet, worksheetName);
 
   return xlsx.write(workbook, { type: 'buffer', bookType: 'xlsx' });
 }