feat(multi-layout): implement form field copying and transformation for multi-page PDF to keep form data (#4314)

app/core/src/main/java/stirling/software/SPDF/controller/api/MultiPageLayoutController.java

@@ -1,6 +1,6 @@
 package stirling.software.SPDF.controller.api;
 
-import java.awt.*;
+import java.awt.Color;
 import java.io.ByteArrayOutputStream;
 import java.io.IOException;
 
@@ -24,15 +24,18 @@ import io.swagger.v3.oas.annotations.Operation;
 import io.swagger.v3.oas.annotations.tags.Tag;
 
 import lombok.RequiredArgsConstructor;
+import lombok.extern.slf4j.Slf4j;
 
 import stirling.software.SPDF.model.api.general.MergeMultiplePagesRequest;
 import stirling.software.common.service.CustomPDFDocumentFactory;
+import stirling.software.common.util.FormUtils;
 import stirling.software.common.util.WebResponseUtils;
 
 @RestController
 @RequestMapping("/api/v1/general")
 @Tag(name = "General", description = "General APIs")
 @RequiredArgsConstructor
+@Slf4j
 public class MultiPageLayoutController {
 
     private final CustomPDFDocumentFactory pdfDocumentFactory;
@@ -103,7 +106,8 @@ public class MultiPageLayoutController {
             float scale = Math.min(scaleWidth, scaleHeight);
 
             int adjustedPageIndex =
-                    i % pagesPerSheet; // This will reset the index for every new page
+                    i % pagesPerSheet; // Close the current content stream and create a new
+            // page and content stream
             int rowIndex = adjustedPageIndex / cols;
             int colIndex = adjustedPageIndex % cols;
 
@@ -131,7 +135,28 @@ public class MultiPageLayoutController {
             }
         }
 
-        contentStream.close(); // Close the final content stream
+        contentStream.close();
+
+        // If any source page is rotated, skip form copying/transformation entirely
+        boolean hasRotation = FormUtils.hasAnyRotatedPage(sourceDocument);
+        if (hasRotation) {
+            log.info("Source document has rotated pages; skipping form field copying.");
+        } else {
+            try {
+                FormUtils.copyAndTransformFormFields(
+                        sourceDocument,
+                        newDocument,
+                        totalPages,
+                        pagesPerSheet,
+                        cols,
+                        rows,
+                        cellWidth,
+                        cellHeight);
+            } catch (Exception e) {
+                log.warn("Failed to copy and transform form fields: {}", e.getMessage(), e);
+            }
+        }
+
         sourceDocument.close();
 
         ByteArrayOutputStream baos = new ByteArrayOutputStream();

app/core/src/test/java/stirling/software/SPDF/controller/api/MultiPageLayoutControllerTest.java

@@ -0,0 +1,116 @@
+package stirling.software.SPDF.controller.api;
+
+import org.apache.pdfbox.pdmodel.PDDocument;
+import org.apache.pdfbox.pdmodel.PDPage;
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.DisplayName;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.extension.ExtendWith;
+import org.mockito.InjectMocks;
+import org.mockito.Mock;
+import org.mockito.Mockito;
+import org.mockito.junit.jupiter.MockitoExtension;
+import org.springframework.http.HttpStatus;
+import org.springframework.http.MediaType;
+import org.springframework.http.ResponseEntity;
+import org.springframework.mock.web.MockMultipartFile;
+
+import stirling.software.SPDF.model.api.general.MergeMultiplePagesRequest;
+import stirling.software.common.service.CustomPDFDocumentFactory;
+
+@ExtendWith(MockitoExtension.class)
+class MultiPageLayoutControllerTest {
+
+    @Mock private CustomPDFDocumentFactory pdfDocumentFactory;
+
+    @InjectMocks private MultiPageLayoutController controller;
+
+    private MockMultipartFile fileWithExt;
+    private MockMultipartFile fileNoExt;
+
+    @BeforeEach
+    void setup() {
+        fileWithExt =
+                new MockMultipartFile(
+                        "fileInput", "test.pdf", "application/pdf", new byte[] {1, 2, 3});
+        fileNoExt =
+                new MockMultipartFile("fileInput", "name", "application/pdf", new byte[] {4, 5, 6});
+    }
+
+    @Test
+    @DisplayName("Rejects non-2/3 and non-perfect-square pagesPerSheet")
+    void invalidPagesPerSheetThrows() {
+        MergeMultiplePagesRequest req = new MergeMultiplePagesRequest();
+        req.setPagesPerSheet(5);
+        req.setAddBorder(Boolean.TRUE);
+        req.setFileInput(fileWithExt);
+
+        Assertions.assertThrows(
+                IllegalArgumentException.class, () -> controller.mergeMultiplePagesIntoOne(req));
+    }
+
+    @Test
+    @DisplayName("Generates PDF and filename suffix for perfect-square layout with no source pages")
+    void perfectSquareNoPages() throws Exception {
+        PDDocument source = new PDDocument();
+        PDDocument target = new PDDocument();
+        Mockito.when(pdfDocumentFactory.load(fileWithExt)).thenReturn(source);
+        Mockito.when(pdfDocumentFactory.createNewDocumentBasedOnOldDocument(source))
+                .thenReturn(target);
+
+        MergeMultiplePagesRequest req = new MergeMultiplePagesRequest();
+        req.setPagesPerSheet(4);
+        req.setAddBorder(Boolean.FALSE);
+        req.setFileInput(fileWithExt);
+
+        ResponseEntity<byte[]> resp = controller.mergeMultiplePagesIntoOne(req);
+        Assertions.assertEquals(HttpStatus.OK, resp.getStatusCode());
+        Assertions.assertEquals(MediaType.APPLICATION_PDF, resp.getHeaders().getContentType());
+        Assertions.assertNotNull(resp.getBody());
+        Assertions.assertTrue(resp.getBody().length > 0);
+        Assertions.assertEquals(
+                "test_layoutChanged.pdf", resp.getHeaders().getContentDisposition().getFilename());
+    }
+
+    @Test
+    @DisplayName("Merges single source page into 2-up layout and returns PDF")
+    void twoUpWithSinglePage() throws Exception {
+        PDDocument source = new PDDocument();
+        source.addPage(new PDPage());
+        PDDocument target = new PDDocument();
+        Mockito.when(pdfDocumentFactory.load(fileWithExt)).thenReturn(source);
+        Mockito.when(pdfDocumentFactory.createNewDocumentBasedOnOldDocument(source))
+                .thenReturn(target);
+
+        MergeMultiplePagesRequest req = new MergeMultiplePagesRequest();
+        req.setPagesPerSheet(2);
+        req.setAddBorder(Boolean.TRUE);
+        req.setFileInput(fileWithExt);
+
+        ResponseEntity<byte[]> resp = controller.mergeMultiplePagesIntoOne(req);
+        Assertions.assertEquals(HttpStatus.OK, resp.getStatusCode());
+        Assertions.assertEquals(MediaType.APPLICATION_PDF, resp.getHeaders().getContentType());
+        Assertions.assertNotNull(resp.getBody());
+        Assertions.assertTrue(resp.getBody().length > 0);
+    }
+
+    @Test
+    @DisplayName("Uses input name without extension and appends suffix for 3-up")
+    void threeUpWithNameNoExtension() throws Exception {
+        PDDocument source = new PDDocument();
+        PDDocument target = new PDDocument();
+        Mockito.when(pdfDocumentFactory.load(fileNoExt)).thenReturn(source);
+        Mockito.when(pdfDocumentFactory.createNewDocumentBasedOnOldDocument(source))
+                .thenReturn(target);
+
+        MergeMultiplePagesRequest req = new MergeMultiplePagesRequest();
+        req.setPagesPerSheet(3);
+        req.setAddBorder(Boolean.TRUE);
+        req.setFileInput(fileNoExt);
+
+        ResponseEntity<byte[]> resp = controller.mergeMultiplePagesIntoOne(req);
+        Assertions.assertEquals(
+                "name_layoutChanged.pdf", resp.getHeaders().getContentDisposition().getFilename());
+    }
+}