new workaround for remove digital signature

src/main/resources/templates/convert/pdf-to-pdfa.html

@@ -21,15 +21,51 @@
               <form method="post" enctype="multipart/form-data" th:action="@{api/v1/convert/pdf/pdfa}">
                 <div th:replace="~{fragments/common :: fileSelector(name='fileInput', multiple=false, accept='application/pdf')}"></div>
                 <div class="mb-3">
-                  <label th:text="#{pdfToPDFA.outputFormat}"></label>
-                  <select class="form-control" name="outputFormat">
+                  <label for="outputFormat" th:text="#{pdfToPDFA.outputFormat}"></label>
+                  <select class="form-control" name="outputFormat" id="outputFormat">
                     <option value="pdfa-1">PDF/A-1b</option>
                     <option value="pdfa">PDF/A-2b</option>
                   </select>
                 </div>
-                <br>
+                <div id="result" class="alert-warning"></div>
                 <button type="submit" id="submitBtn" class="btn btn-primary" th:text="#{pdfToPDFA.submit}"></button>
               </form>
+              <script th:inline="javascript">
+                document.getElementById('fileInput-input').addEventListener('change', async () => {
+                  pdfjsLib.GlobalWorkerOptions.workerSrc = './pdfjs/pdf.worker.mjs';
+                  const fileInput = document.getElementById('fileInput-input');
+                  const resultDiv = document.getElementById('result');
+
+                  const file = fileInput.files[0];
+                  const arrayBuffer = await file.arrayBuffer();
+
+                  try {
+                    const pdf = await pdfjsLib.getDocument({ data: arrayBuffer }).promise;
+                    
+                    let hasSignature = false;
+
+                    for (let i = 1; i <= pdf.numPages; i++) {
+                      const page = await pdf.getPage(i);
+                      const annotations = await page.getAnnotations({ intent: 'display' });
+
+                      annotations.forEach(annotation => {
+                        console.log(annotation)
+                        if (annotation.subtype === 'Widget' && annotation.fieldType === 'Sig') {
+                          hasSignature = true;
+                        }
+                      });
+                    }
+
+                    if (hasSignature) {
+                      /*<![CDATA[*/
+                      resultDiv.textContent = /*[[#{pdfToPDFA.pdfWithDigitalSignature}]]*/ "The PDF contains a digital signature.";
+                      /*]]>*/
+                    }
+                  } catch (error) {
+                    resultDiv.textContent = 'Error reading the PDF: ' + error.message;
+                  }
+              });
+              </script>
               <p class="mt-3" th:text="#{pdfToPDFA.credit}"></p>
             </div>
           </div>