feat: implement PDF attachment editing functionality with web worker support

- Added a new worker script to handle editing of embedded attachments in PDF files.
- Created TypeScript definitions for message structures and response types related to attachment editing.
- Updated the main logic to utilize the worker for improved performance and responsiveness during attachment management.
- Integrated the editing feature into the UI, allowing users to view, remove, or replace attachments in their PDFs.
- Enhanced error handling and user feedback during the editing process.

public/workers/edit-attachments.worker.d.ts

@@ -0,0 +1,42 @@
+declare const coherentpdf: typeof import('../../src/types/coherentpdf.global').coherentpdf;
+
+interface GetAttachmentsMessage {
+  command: 'get-attachments';
+  fileBuffer: ArrayBuffer;
+  fileName: string;
+}
+
+interface EditAttachmentsMessage {
+  command: 'edit-attachments';
+  fileBuffer: ArrayBuffer;
+  fileName: string;
+  attachmentsToRemove: number[];
+}
+
+type EditAttachmentsWorkerMessage = GetAttachmentsMessage | EditAttachmentsMessage;
+
+interface GetAttachmentsSuccessResponse {
+  status: 'success';
+  attachments: Array<{ index: number; name: string; page: number; data: ArrayBuffer }>;
+  fileName: string;
+}
+
+interface GetAttachmentsErrorResponse {
+  status: 'error';
+  message: string;
+}
+
+interface EditAttachmentsSuccessResponse {
+  status: 'success';
+  modifiedPDF: ArrayBuffer;
+  fileName: string;
+}
+
+interface EditAttachmentsErrorResponse {
+  status: 'error';
+  message: string;
+}
+
+type GetAttachmentsResponse = GetAttachmentsSuccessResponse | GetAttachmentsErrorResponse;
+type EditAttachmentsResponse = EditAttachmentsSuccessResponse | EditAttachmentsErrorResponse;
+type EditAttachmentsWorkerResponse = GetAttachmentsResponse | EditAttachmentsResponse;

public/workers/edit-attachments.worker.js

@@ -0,0 +1,151 @@
+self.importScripts('/coherentpdf.browser.min.js');
+
+function getAttachmentsFromPDFInWorker(fileBuffer, fileName) {
+  try {
+    const uint8Array = new Uint8Array(fileBuffer);
+    
+    let pdf;
+    try {
+      pdf = coherentpdf.fromMemory(uint8Array, '');
+    } catch (error) {
+      self.postMessage({
+        status: 'error',
+        message: `Failed to load PDF: ${fileName}. Error: ${error.message || error}`
+      });
+      return;
+    }
+
+    coherentpdf.startGetAttachments(pdf);
+    const attachmentCount = coherentpdf.numberGetAttachments();
+
+    if (attachmentCount === 0) {
+      self.postMessage({
+        status: 'success',
+        attachments: [],
+        fileName: fileName
+      });
+      coherentpdf.deletePdf(pdf);
+      return;
+    }
+
+    const attachments = [];
+    for (let i = 0; i < attachmentCount; i++) {
+      try {
+        const name = coherentpdf.getAttachmentName(i);
+        const page = coherentpdf.getAttachmentPage(i);
+        const attachmentData = coherentpdf.getAttachmentData(i);
+
+        const dataArray = new Uint8Array(attachmentData);
+        const buffer = dataArray.buffer.slice(dataArray.byteOffset, dataArray.byteOffset + dataArray.byteLength);
+
+        attachments.push({
+          index: i,
+          name: String(name),  
+          page: Number(page), 
+          data: buffer
+        });
+      } catch (error) {
+        console.warn(`Failed to get attachment ${i} from ${fileName}:`, error);
+      }
+    }
+
+    coherentpdf.endGetAttachments();
+    coherentpdf.deletePdf(pdf);
+
+    const response = {
+      status: 'success',
+      attachments: attachments,
+      fileName: fileName
+    };
+
+    const transferBuffers = attachments.map(att => att.data);
+    self.postMessage(response, transferBuffers);
+  } catch (error) {
+    self.postMessage({
+      status: 'error',
+      message: error instanceof Error
+        ? error.message
+        : 'Unknown error occurred during attachment listing.'
+    });
+  }
+}
+
+function editAttachmentsInPDFInWorker(fileBuffer, fileName, attachmentsToRemove) {
+  try {
+    const uint8Array = new Uint8Array(fileBuffer);
+    
+    let pdf;
+    try {
+      pdf = coherentpdf.fromMemory(uint8Array, '');
+    } catch (error) {
+      self.postMessage({
+        status: 'error',
+        message: `Failed to load PDF: ${fileName}. Error: ${error.message || error}`
+      });
+      return;
+    }
+
+    if (attachmentsToRemove && attachmentsToRemove.length > 0) {
+      coherentpdf.startGetAttachments(pdf);
+      const attachmentCount = coherentpdf.numberGetAttachments();
+      const attachmentsToKeep = [];
+      
+      for (let i = 0; i < attachmentCount; i++) {
+        if (!attachmentsToRemove.includes(i)) {
+          const name = coherentpdf.getAttachmentName(i);
+          const page = coherentpdf.getAttachmentPage(i);
+          const data = coherentpdf.getAttachmentData(i);
+          
+          const dataCopy = new Uint8Array(data.length);
+          dataCopy.set(new Uint8Array(data));
+          
+          attachmentsToKeep.push({ 
+            name: String(name), 
+            page: Number(page),  
+            data: dataCopy 
+          });
+        }
+      }
+      
+      coherentpdf.endGetAttachments();
+
+      coherentpdf.removeAttachedFiles(pdf);
+      
+      for (const attachment of attachmentsToKeep) {
+        if (attachment.page === 0) {
+          coherentpdf.attachFileFromMemory(attachment.data, attachment.name, pdf);
+        } else {
+          coherentpdf.attachFileToPageFromMemory(attachment.data, attachment.name, pdf, attachment.page);
+        }
+      }
+    }
+    
+    const modifiedBytes = coherentpdf.toMemory(pdf, false, true);
+    coherentpdf.deletePdf(pdf);
+
+    const buffer = modifiedBytes.buffer.slice(modifiedBytes.byteOffset, modifiedBytes.byteOffset + modifiedBytes.byteLength);
+
+    const response = {
+      status: 'success',
+      modifiedPDF: buffer,
+      fileName: fileName
+    };
+
+    self.postMessage(response, [response.modifiedPDF]);
+  } catch (error) {
+    self.postMessage({
+      status: 'error',
+      message: error instanceof Error
+        ? error.message
+        : 'Unknown error occurred during attachment editing.'
+    });
+  }
+}
+
+self.onmessage = (e) => {
+  if (e.data.command === 'get-attachments') {
+    getAttachmentsFromPDFInWorker(e.data.fileBuffer, e.data.fileName);
+  } else if (e.data.command === 'edit-attachments') {
+    editAttachmentsInPDFInWorker(e.data.fileBuffer, e.data.fileName, e.data.attachmentsToRemove);
+  }
+};