feat: implement checksum-based duplicate detection for split email attachments

paperless-backend/src/email/email-import.controller.ts

@@ -67,6 +67,17 @@ export class EmailImportController {
     return { success: true };
   }
 
+  // --- Split Checksum Check ---
+  @Post('attachments/:attachmentId/check-split-checksum')
+  @RequirePermissions(Permission.VIEW_MAIL)
+  async checkSplitChecksum(
+    @Param('attachmentId') attachmentId: number,
+    @Body() body: { pages: { start: number; end: number } },
+  ) {
+    const isDuplicate = await this.importService.checkSplitChecksum(attachmentId, body.pages);
+    return { isDuplicate };
+  }
+
   // --- Print Preview ---
   @Post('attachments/:attachmentId/print-preview')
   @RequirePermissions(Permission.VIEW_MAIL)

paperless-backend/src/email/email-import.service.ts

@@ -16,6 +16,7 @@ import { PdfService } from '../preprocessing/pdf.service';
 import * as path from 'path';
 import * as os from 'os';
 import * as fs from 'fs/promises';
+import * as crypto from 'crypto';
 
 @Injectable()
 export class EmailImportService {
@@ -154,6 +155,25 @@ export class EmailImportService {
     }
   }
 
+  // --- Checksum Check for Split Documents ---
+  async checkSplitChecksum(attachmentId: number, pages: { start: number; end: number }): Promise<boolean> {
+    const content = await this.contentRepo.findOne({ where: { AttachmentEntityId: attachmentId } });
+    if (!content) return false;
+
+    const pdfDoc = await PDFDocument.load(content.Content1, { ignoreEncryption: true });
+    const total = pdfDoc.getPageCount();
+    const startIdx = Math.max(1, pages.start) - 1;
+    const endIdx = Math.min(pages.end === 999 ? total : pages.end, total) - 1;
+
+    const sliced = await PDFDocument.create();
+    const indices = Array.from({ length: endIdx - startIdx + 1 }, (_, i) => startIdx + i);
+    const copied = await sliced.copyPages(pdfDoc, indices);
+    copied.forEach(p => sliced.addPage(p));
+
+    const checksum = crypto.createHash('md5').update(Buffer.from(await sliced.save())).digest('hex');
+    return this.paperlessService.checksumExists(checksum);
+  }
+
   // --- Print Preview ---
   async generatePrintPdf(attachmentId: number, barcodeData: any): Promise<Buffer> {
     const content = await this.contentRepo.findOne({ where: { AttachmentEntityId: attachmentId } });

paperless-frontend/src/api/email-import.ts

@@ -57,6 +57,11 @@ export const emailImportApi = {
     return res.data;
   },
 
+  checkSplitChecksum: async (attachmentId: number, pages: { start: number; end: number }): Promise<boolean> => {
+    const res = await api.post<{ isDuplicate: boolean }>(`/api/email-import/attachments/${attachmentId}/check-split-checksum`, { pages });
+    return res.data.isDuplicate;
+  },
+
   executeImport: async (emailDate: string, attachments: AttachmentImportData[]): Promise<{ success: boolean; results: any[] }> => {
     const res = await api.post('/api/email-import/execute', { emailDate, attachments });
     return res.data;

paperless-frontend/src/components/MailImportWizard.tsx

@@ -131,19 +131,20 @@ export default function MailImportWizard({ visible, onClose, email, attachments
     setImportData(prev => prev.map(item => item.virtualId === virtualId ? { ...item, [key]: value } : item));
   };
 
-  const handleSplit = (virtualId: string, splitPage: number) => {
+  const handleSplit = async (virtualId: string, splitPage: number) => {
-    setImportData(prev => {
+    const idx = importData.findIndex(i => i.virtualId === virtualId);
-      const idx = prev.findIndex(i => i.virtualId === virtualId);
+    if (idx === -1) return;
-      if (idx === -1) return prev;
 
-      const itemToSplit = prev[idx];
+    const itemToSplit = importData[idx];
     const start = itemToSplit.pages?.start || 1;
-      const end = itemToSplit.pages?.end || 999; // 999 means to the end
+    const end = itemToSplit.pages?.end || 999;
 
-      const part1 = { ...itemToSplit, virtualId: `${itemToSplit.attachmentId}_${start}_${splitPage}`, pages: { start, end: splitPage }, fileName: `${itemToSplit.fileName} (Teil 1)` };
+    const part1Pages = { start, end: splitPage };
-      const part2 = { ...itemToSplit, virtualId: `${itemToSplit.attachmentId}_${splitPage+1}_${end}`, pages: { start: splitPage + 1, end }, fileName: `${itemToSplit.fileName} (Teil 2)` };
+    const part2Pages = { start: splitPage + 1, end };
+
+    const part1 = { ...itemToSplit, virtualId: `${itemToSplit.attachmentId}_${start}_${splitPage}`, pages: part1Pages, fileName: `${itemToSplit.fileName} (Teil 1)` };
+    const part2 = { ...itemToSplit, virtualId: `${itemToSplit.attachmentId}_${splitPage+1}_${end}`, pages: part2Pages, fileName: `${itemToSplit.fileName} (Teil 2)` };
 
-      // Propagate date and barcode
     const parentDate = eingangsdaten[virtualId] || dayjs(email.Date);
     const parentBarcode = barcodes[virtualId];
 
@@ -161,10 +162,28 @@ export default function MailImportWizard({ visible, onClose, email, attachments
       }));
     }
 
+    setImportData(prev => {
       const newArray = [...prev];
       newArray.splice(idx, 1, part1, part2);
       return newArray;
     });
+
+    // Checksumme der geteilten Teile prüfen
+    try {
+      const [dup1, dup2] = await Promise.all([
+        emailImportApi.checkSplitChecksum(itemToSplit.attachmentId, part1Pages),
+        emailImportApi.checkSplitChecksum(itemToSplit.attachmentId, part2Pages),
+      ]);
+      if (dup1 || dup2) {
+        setImportData(prev => prev.map(item => {
+          if (item.virtualId === part1.virtualId && dup1) return { ...item, isDuplicate: true, type: 'IGNORE' as const };
+          if (item.virtualId === part2.virtualId && dup2) return { ...item, isDuplicate: true, type: 'IGNORE' as const };
+          return item;
+        }));
+      }
+    } catch (e) {
+      console.error('Fehler bei Checksummen-Prüfung nach Split', e);
+    }
   };
 
   const loadBelegnummern = async () => {