refactor(qpdf): move initialization logic to helpers module

Consolidate qpdf initialization code into helpers.ts to avoid duplication
Improve error message for password protected PDFs
Fortify encryption logic by auto-filling owner password when empty

src/js/logic/change-permissions.ts

@@ -1,31 +1,6 @@
 import { showLoader, hideLoader, showAlert } from '../ui.js';
-import { downloadFile, readFileAsArrayBuffer } from '../utils/helpers.js';
+import { downloadFile, initializeQpdf, readFileAsArrayBuffer } from '../utils/helpers.js';
 import { state } from '../state.js';
-import createModule from '@neslinesli93/qpdf-wasm';
-
-let qpdfInstance: any = null;
-
-async function initializeQpdf() {
-  if (qpdfInstance) {
-    return qpdfInstance;
-  }
-  showLoader('Initializing PDF engine...');
-  try {
-    qpdfInstance = await createModule({
-      locateFile: () => '/qpdf.wasm',
-    });
-  } catch (error) {
-    console.error('Failed to initialize qpdf-wasm:', error);
-    showAlert(
-      'Initialization Error',
-      'Could not load the PDF engine. Please refresh the page and try again.'
-    );
-    throw error;
-  } finally {
-    hideLoader();
-  }
-  return qpdfInstance;
-}
 
 export async function changePermissions() {
   const file = state.files[0];
@@ -156,7 +131,7 @@ export async function changePermissions() {
     } else {
       showAlert(
         'Processing Failed',
-        `An error occurred: ${error.message || 'The PDF might be corrupted.'}`
+        `An error occurred: ${error.message || 'The PDF might be corrupted or password protected.'}`
       );
     }
   } finally {

src/js/logic/decrypt.ts

@@ -1,31 +1,6 @@
 import { showLoader, hideLoader, showAlert } from '../ui.js';
-import { downloadFile, readFileAsArrayBuffer } from '../utils/helpers.js';
+import { downloadFile, initializeQpdf, readFileAsArrayBuffer } from '../utils/helpers.js';
 import { state } from '../state.js';
-import createModule from '@neslinesli93/qpdf-wasm';
-
-let qpdfInstance: any = null;
-
-async function initializeQpdf() {
-  if (qpdfInstance) {
-    return qpdfInstance;
-  }
-  showLoader('Initializing decryption engine...');
-  try {
-    qpdfInstance = await createModule({
-      locateFile: () => '/qpdf.wasm',
-    });
-  } catch (error) {
-    console.error('Failed to initialize qpdf-wasm:', error);
-    showAlert(
-      'Initialization Error',
-      'Could not load the decryption engine. Please refresh the page and try again.'
-    );
-    throw error;
-  } finally {
-    hideLoader();
-  }
-  return qpdfInstance;
-}
 
 export async function decrypt() {
   const file = state.files[0];

src/js/logic/encrypt.ts

@@ -1,38 +1,13 @@
 import { showLoader, hideLoader, showAlert } from '../ui.js';
-import { downloadFile, readFileAsArrayBuffer } from '../utils/helpers.js';
+import { downloadFile, initializeQpdf, readFileAsArrayBuffer } from '../utils/helpers.js';
 import { state } from '../state.js';
-import createModule from '@neslinesli93/qpdf-wasm';
-
-let qpdfInstance: any = null;
-
-async function initializeQpdf() {
-  if (qpdfInstance) {
-    return qpdfInstance;
-  }
-  showLoader('Initializing encryption engine...');
-  try {
-    qpdfInstance = await createModule({
-      locateFile: () => '/qpdf.wasm',
-    });
-  } catch (error) {
-    console.error('Failed to initialize qpdf-wasm:', error);
-    showAlert(
-      'Initialization Error',
-      'Could not load the encryption engine. Please refresh the page and try again.'
-    );
-    throw error;
-  } finally {
-    hideLoader();
-  }
-  return qpdfInstance;
-}
 
 export async function encrypt() {
   const file = state.files[0];
   const userPassword =
     (document.getElementById('user-password-input') as HTMLInputElement)
       ?.value || '';
-  const ownerPassword =
+  const ownerPasswordInput =
     (document.getElementById('owner-password-input') as HTMLInputElement)
       ?.value || '';
 
@@ -41,6 +16,9 @@ export async function encrypt() {
     return;
   }
 
+  const ownerPassword = ownerPasswordInput || userPassword;
+  const hasDistinctOwnerPassword = ownerPasswordInput !== '';
+
   const inputPath = '/input.pdf';
   const outputPath = '/output.pdf';
   let qpdf: any;
@@ -61,11 +39,12 @@ export async function encrypt() {
       inputPath,
       '--encrypt',
       userPassword,
-      ownerPassword, // Can be empty
+      ownerPassword, 
       '256',
     ];
 
-    if (ownerPassword) {
+    // Only add restrictions if a distinct owner password was provided
+    if (hasDistinctOwnerPassword) {
       args.push(
         '--modify=none',
         '--extract=n', 
@@ -78,12 +57,10 @@ export async function encrypt() {
       );
     }
 
-    if (!ownerPassword) {
-      args.push('--allow-insecure');
-    }
-
     args.push('--', outputPath);
 
+    console.log(args);
+
     try {
       qpdf.callMain(args);
     } catch (qpdfError: any) {
@@ -106,9 +83,9 @@ export async function encrypt() {
     hideLoader();
 
     let successMessage = 'PDF encrypted successfully with 256-bit AES!';
-    if (!ownerPassword) {
+    if (!hasDistinctOwnerPassword) {
       successMessage +=
-        ' Note: Without an owner password, the PDF has no usage restrictions.';
+        ' Note: Without a separate owner password, the PDF has no usage restrictions.';
     }
 
     showAlert('Success', successMessage);

src/js/utils/helpers.ts

@@ -1,3 +1,6 @@
+import createModule from '@neslinesli93/qpdf-wasm';
+import { showLoader, hideLoader, showAlert } from '../ui';
+
 const STANDARD_SIZES = {
   A4: { width: 595.28, height: 841.89 },
   Letter: { width: 612, height: 792 },
@@ -146,3 +149,31 @@ export function formatIsoDate(isoDateString) {
     return isoDateString; // Return original string on any error
   }
 }
+
+let qpdfInstance: any = null;
+
+/**
+ * Initialize qpdf-wasm singleton.
+ * Subsequent calls return the same instance.
+ */
+export async function initializeQpdf() {
+  if (qpdfInstance) return qpdfInstance;
+
+  showLoader('Initializing PDF engine...');
+  try {
+    qpdfInstance = await createModule({
+      locateFile: () => '/qpdf.wasm',
+    });
+  } catch (error) {
+    console.error('Failed to initialize qpdf-wasm:', error);
+    showAlert(
+      'Initialization Error',
+      'Could not load the PDF engine. Please refresh the page and try again.'
+    );
+    throw error;
+  } finally {
+    hideLoader();
+  }
+
+  return qpdfInstance;
+}