Methods for PeppolBillingApi to find country identifier of supplier a…

…nd customer party

These values can be useful for mandatory header property COUNTRY_C1 and corresponding
PEPPOL End User and Transmission report

api/src/main/java/peppol/bis/invoice3/api/PeppolBillingApi.java

@@ -71,6 +71,14 @@ public boolean isInvoice() {
         return false;
     }
 
+    public String getSupplierCountryIdentifier() {
+        return (String) ((Document) this.object).find("AccountingSupplierParty", "Party", "PostalAddress", "Country", "IdentificationCode").single().children().get(0).text();
+    }
+
+    public String getCustomerCountryIdentifier() {
+        return (String) ((Document) this.object).find("AccountingCustomerParty", "Party", "PostalAddress", "Country", "IdentificationCode").single().children().get(0).text();
+    }
+
     public String prettyPrint() {
         return XML_FIRST_LINE + (this.object instanceof BillingCommon ? ((BillingCommon) this.object).xmlRoot() : ((Document) this.object).getRootElement()).toIndentedXML();
     }

api/src/test/java/peppol/bis/invoice3/api/PeppolBillingApiTest.java

@@ -0,0 +1,41 @@
+/**
+ * Copyright (C) Posten Norge AS
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *         http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package peppol.bis.invoice3.api;
+
+import org.eaxy.Document;
+import org.eaxy.Xml;
+import org.junit.jupiter.api.Test;
+
+import java.io.IOException;
+import java.io.InputStream;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertNotNull;
+
+class PeppolBillingApiTest {
+
+    @Test
+    public void test() throws IOException {
+        try (InputStream inputStream = PeppolBillingApiTest.class.getResourceAsStream("/norwegian-example.xml")) {
+            assertNotNull(inputStream);
+            Document document = Xml.xml(new String(inputStream.readAllBytes()));
+            PeppolBillingApi<Document> peppolBillingApi = new PeppolBillingApi<>(document);
+            assertEquals("NO", peppolBillingApi.getCustomerCountryIdentifier());
+            assertEquals("NO", peppolBillingApi.getSupplierCountryIdentifier());
+        }
+    }
+
+}