From 882d50958059bb2a3ba5e1885e0d0ff76dbd4192 Mon Sep 17 00:00:00 2001
From: jstaerk <jstaerk@usegroup.de>
Date: Wed, 15 Oct 2025 12:41:24 +0200
Subject: [PATCH] If the interface is implemented correctly, ZF2EdgeTest now
 already writes a BT-17 incl Date

---
 .../ZUGFeRD/IDatedReference.java              | 10 ++++++++++
 .../ZUGFeRD/IExportableTransaction.java       |  9 +++++++++
 .../mustangproject/ZUGFeRD/ZF2EdgeTest.java   | 19 +++++++++++++++++++
 3 files changed, 38 insertions(+)
 create mode 100644 library/src/main/java/org/mustangproject/ZUGFeRD/IDatedReference.java

diff --git a/library/src/main/java/org/mustangproject/ZUGFeRD/IDatedReference.java b/library/src/main/java/org/mustangproject/ZUGFeRD/IDatedReference.java
new file mode 100644
index 00000000..af1adf38
--- /dev/null
+++ b/library/src/main/java/org/mustangproject/ZUGFeRD/IDatedReference.java
@@ -0,0 +1,10 @@
+package org.mustangproject.ZUGFeRD;
+
+import java.util.Date;
+
+public interface IDatedReference {
+	public String getID();
+	default Date getDate() {
+		return null;
+	}
+}
diff --git a/library/src/main/java/org/mustangproject/ZUGFeRD/IExportableTransaction.java b/library/src/main/java/org/mustangproject/ZUGFeRD/IExportableTransaction.java
index c7a6d903..72b61d83 100644
--- a/library/src/main/java/org/mustangproject/ZUGFeRD/IExportableTransaction.java
+++ b/library/src/main/java/org/mustangproject/ZUGFeRD/IExportableTransaction.java
@@ -214,6 +214,15 @@ public interface IExportableTransaction {
 		return null;
 	}
 
+	/**
+	 * BT-17 tender or lot reference
+	 *
+	 * @return mandatory ID, optional Date
+	 */
+	default IDatedReference getTenderReference() {
+		return null;
+	}
+
 	/**
 	 * own name
 	 *
diff --git a/library/src/test/java/org/mustangproject/ZUGFeRD/ZF2EdgeTest.java b/library/src/test/java/org/mustangproject/ZUGFeRD/ZF2EdgeTest.java
index f095372b..3178c321 100644
--- a/library/src/test/java/org/mustangproject/ZUGFeRD/ZF2EdgeTest.java
+++ b/library/src/test/java/org/mustangproject/ZUGFeRD/ZF2EdgeTest.java
@@ -144,6 +144,25 @@ public class ZF2EdgeTest extends MustangReaderTestCase {
 		return "DE";
 	}
 
+	@Override
+	public IDatedReference getTenderReference() {
+		return new IDatedReference() {
+			@Override
+			public String getID() {
+				return "983-jk-787 (obsolete)";
+			}
+			@Override
+			public Date getDate() {
+				SimpleDateFormat sdf=new SimpleDateFormat("YYYY-mm-dd");
+				try {
+					return sdf.parse("2025-10-12");
+				} catch (ParseException e) {
+					// wont happen, I promise :-)
+				}
+			}
+		};
+	}
+
 	@Override
 	public String getOwnLocation() {
 		return "Stadthausen";