PDFBOX-6009: recalculate ParentTreeNextKey because it might be missing

git-svn-id: https://svn.apache.org/repos/asf/pdfbox/trunk@1925629 13f79535-47bb-0310-9956-ffa450edef68

Author: THausherr

pdfbox/src/main/java/org/apache/pdfbox/multipdf/Splitter.java

@@ -23,6 +23,7 @@
 import java.util.LinkedHashMap;
 import java.util.List;
 import java.util.Map;
+import java.util.Optional;
 import java.util.Set;
 
 import org.apache.logging.log4j.Logger;
@@ -236,7 +237,13 @@ private void cloneStructureTree(PDDocument destinationDocument) throws IOExcepti
         dstNumberTreeNode.setNumbers(dstNumberTreeAsMap);
         dstStructureTreeRoot.setParentTree(dstNumberTreeNode);
 
-        dstStructureTreeRoot.setParentTreeNextKey(srcStructureTreeRoot.getParentTreeNextKey());
+        // get highest key + 1
+        Optional<Integer> max = dstNumberTreeAsMap.keySet().stream().max(Integer::compareTo);
+        if (max.isPresent())
+        {
+            dstStructureTreeRoot.setParentTreeNextKey(max.get() + 1);
+        }
+
         dstStructureTreeRoot.setClassMap(srcStructureTreeRoot.getClassMap());
         cloneRoleMap(srcStructureTreeRoot, dstStructureTreeRoot);
         cloneIDTree(srcStructureTreeRoot, dstStructureTreeRoot);

pdfbox/src/test/java/org/apache/pdfbox/multipdf/PDFMergerUtilityTest.java

@@ -663,6 +663,7 @@ void checkWithNumberTree(PDDocument document) throws IOException
     {
         PDDocumentCatalog documentCatalog = document.getDocumentCatalog();
         PDNumberTreeNode parentTree = documentCatalog.getStructureTreeRoot().getParentTree();
+        assertNotEquals(-1, documentCatalog.getStructureTreeRoot().getParentTreeNextKey());
         Map<Integer, COSObjectable> numberTreeAsMap = PDFMergerUtility.getNumberTreeAsMap(parentTree);
         Set<Integer> keySet = numberTreeAsMap.keySet();
         PDAcroForm acroForm = documentCatalog.getAcroForm();