be able to parse minimal invoices

library/src/main/java/org/mustangproject/CalculatedInvoice.java

@@ -0,0 +1,30 @@
+// Copyright (c) 2023 Jochen Stärk, see LICENSE file
+package org.mustangproject;
+
+
+import org.mustangproject.ZUGFeRD.TransactionCalculator;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.io.Serializable;
+import java.math.BigDecimal;
+
+public class CalculatedInvoice extends Invoice implements Serializable {
+
+    protected BigDecimal grandTotal=null;
+
+    public void calculate() {
+        TransactionCalculator tc=new TransactionCalculator(this);
+        grandTotal=tc.getGrandTotal();
+    }
+	public BigDecimal getGrandTotal() {
+		if (grandTotal==null) {
+			calculate();
+		}
+		return grandTotal;
+	}
+	public CalculatedInvoice setGrandTotal(BigDecimal grand) {
+		grandTotal=grand;
+		return this;
+	}
+}

library/src/main/java/org/mustangproject/ZUGFeRD/ZUGFeRDImporter.java

@@ -394,9 +394,7 @@ public class ZUGFeRDImporter extends ZUGFeRDInvoiceImporter {
 	 */
 	public String getAmount() {
 
-		TransactionCalculator ic=new TransactionCalculator(importedInvoice);
-
-		return ic.getGrandTotal().toPlainString();
+		return importedInvoice.getGrandTotal().toPlainString();
 	}
 
 

library/src/main/java/org/mustangproject/ZUGFeRD/ZUGFeRDInvoiceImporter.java

@@ -67,7 +67,7 @@ public class ZUGFeRDInvoiceImporter {
 	 */
 	protected boolean parseAutomatically = true;
 	protected Integer version;
-	protected Invoice importedInvoice = null;
+	protected CalculatedInvoice importedInvoice = null;
 	protected boolean recalcPrice = false;
 	protected boolean ignoreCalculationErrors = false;
 	protected ArrayList<FileAttachment> fileAttachments = new ArrayList<>();
@@ -239,7 +239,7 @@ public class ZUGFeRDInvoiceImporter {
 		document = builder.parse(is);
 		if (parseAutomatically) {
 			try {
-				importedInvoice = new Invoice();
+				importedInvoice = new CalculatedInvoice();
 				extractInto(importedInvoice);
 			} catch (XPathExpressionException e) {
 				throw new RuntimeException(e);
@@ -281,6 +281,12 @@ public class ZUGFeRDInvoiceImporter {
 		NodeList totalNodes = (NodeList) xpr.evaluate(getDocument(), XPathConstants.NODESET);
 		if (totalNodes.getLength() > 0) {
 			expectedGrandTotal = new BigDecimal(totalNodes.item(0).getTextContent());
+			if (zpp instanceof CalculatedInvoice) {
+				// usually we would re-calculate the invoice to get expectedGrandTotal
+				// however, for "minimal" invoices or other invoices without lines
+				// this will not work
+				((CalculatedInvoice) zpp).setGrandTotal(expectedGrandTotal);
+			}
 		}
 
 		Date issueDate = null;

library/src/test/java/org/mustangproject/ZUGFeRD/ProfilesMinimumBasicWLTest.java

@@ -136,7 +136,7 @@ public class ProfilesMinimumBasicWLTest extends TestCase {
 		ZUGFeRDImporter zi = new ZUGFeRDImporter(TARGET_PDF_FX_MINIMUM);
 
 		// Reading ZUGFeRD
-		assertEquals("145.37",zi.getAmount());
+		assertEquals("146.37",zi.getAmount());
 //		assertEquals(zi.getBIC(), ownBIC);
 //		assertEquals(zi.getIBAN(), ownIBAN);
 		assertEquals(ownOrgName, zi.getHolder());