remove case-insensitive duplicates for notification destination

Author: leoclee

src/main/java/org/nhindirect/stagent/mail/notifications/NotificationHelper.java

@@ -25,6 +25,8 @@ STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 import java.util.ArrayList;
 import java.util.Collection;
 import java.util.Collections;
+import java.util.List;
+import java.util.TreeSet;
 import java.util.Arrays;
 
 import javax.mail.MessagingException;
@@ -107,11 +109,23 @@ public static String getNotificationDestination(Message message)
 
     	try
     	{
-    		retVal = message.getHeader(MDNStandard.Headers.DispositionNotificationTo, ",");
-    		
-    		if (retVal == null || retVal.isEmpty())
-    		{
-    			retVal = message.getHeader(MDNStandard.Headers.From, ",");
+    		String[] destinations = message.getHeader(MDNStandard.Headers.DispositionNotificationTo);
+
+    		if (destinations == null || destinations.length == 0) {
+    			destinations = message.getHeader(MDNStandard.Headers.From);
+    		}
+
+    		if (destinations == null || destinations.length == 0) {
+    			retVal = "";
+    		} else if (destinations.length == 1) {
+    			retVal = destinations[0];
+    		} else if (destinations.length > 1) {
+    			// remove (case-insensitive) duplicates
+    			List<String> uniqueDestinations = new ArrayList<>();
+    			Collections.addAll(uniqueDestinations, destinations);
+    			TreeSet<String> seen = new TreeSet<>(String.CASE_INSENSITIVE_ORDER);
+    			uniqueDestinations.removeIf(s -> !seen.add(s));
+    			retVal = String.join(",", uniqueDestinations);
     		}
     	}
     	catch (MessagingException e) {/* no-op */}

src/test/java/org/nhindirect/stagent/mail/notifications/NotificationHelperTest.java

@@ -0,0 +1,96 @@
+package org.nhindirect.stagent.mail.notifications;
+
+import static org.junit.Assert.assertEquals;
+import static org.mockito.Mockito.when;
+
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.mockito.Mock;
+import org.mockito.junit.MockitoJUnitRunner;
+import org.nhindirect.stagent.mail.Message;
+
+@RunWith(MockitoJUnitRunner.class)
+public class NotificationHelperTest {
+	@Mock
+	private Message mockMessage;
+	private static final String DISPOSITION_NOTIFICATION_TO = "a@test.com";
+	private static final String FROM = "b@test.com";
+
+	@Test
+	public void testNoDestination() throws Exception {
+		String destination = NotificationHelper.getNotificationDestination(mockMessage);
+
+		assertEquals("", destination);
+	}
+
+	@Test
+	public void testDispositionNotification() throws Exception {
+		when(mockMessage.getHeader(MDNStandard.Headers.DispositionNotificationTo))
+				.thenReturn(new String[] { DISPOSITION_NOTIFICATION_TO });
+
+		String destination = NotificationHelper.getNotificationDestination(mockMessage);
+
+		assertEquals(DISPOSITION_NOTIFICATION_TO, destination);
+	}
+
+	@Test
+	public void testDispositionNotificationTo() throws Exception {
+		when(mockMessage.getHeader(MDNStandard.Headers.DispositionNotificationTo))
+				.thenReturn(new String[] { DISPOSITION_NOTIFICATION_TO });
+
+		String destination = NotificationHelper.getNotificationDestination(mockMessage);
+
+		assertEquals(DISPOSITION_NOTIFICATION_TO, destination);
+	}
+
+	@Test
+	public void testMultipleDispositionNotificationTo() throws Exception {
+		String anotherAddress = "anotheraddress@test.com";
+		when(mockMessage.getHeader(MDNStandard.Headers.DispositionNotificationTo))
+				.thenReturn(new String[] { DISPOSITION_NOTIFICATION_TO, anotherAddress });
+
+		String destination = NotificationHelper.getNotificationDestination(mockMessage);
+
+		assertEquals(DISPOSITION_NOTIFICATION_TO + "," + anotherAddress, destination);
+	}
+
+	@Test
+	public void testNullDispositionNotificationTo_FromAsFallback() throws Exception {
+		when(mockMessage.getHeader(MDNStandard.Headers.DispositionNotificationTo)).thenReturn(null);
+		when(mockMessage.getHeader(MDNStandard.Headers.From)).thenReturn(new String[] { FROM });
+
+		String destination = NotificationHelper.getNotificationDestination(mockMessage);
+
+		assertEquals(FROM, destination);
+	}
+
+	@Test
+	public void testEmptyDispositionNotificationTo_FromAsFallback() throws Exception {
+		when(mockMessage.getHeader(MDNStandard.Headers.DispositionNotificationTo)).thenReturn(new String[] {});
+		when(mockMessage.getHeader(MDNStandard.Headers.From)).thenReturn(new String[] { FROM });
+
+		String destination = NotificationHelper.getNotificationDestination(mockMessage);
+
+		assertEquals(FROM, destination);
+	}
+
+	@Test
+	public void testDispositionNotificationToDuplicatesAreRemoved() throws Exception {
+		when(mockMessage.getHeader(MDNStandard.Headers.DispositionNotificationTo))
+				.thenReturn(new String[] { DISPOSITION_NOTIFICATION_TO, DISPOSITION_NOTIFICATION_TO.toUpperCase() });
+
+		String destination = NotificationHelper.getNotificationDestination(mockMessage);
+
+		assertEquals(DISPOSITION_NOTIFICATION_TO, destination);
+	}
+
+	@Test
+	public void testFromDuplicatesAreRemoved() throws Exception {
+		when(mockMessage.getHeader(MDNStandard.Headers.DispositionNotificationTo)).thenReturn(null);
+		when(mockMessage.getHeader(MDNStandard.Headers.From)).thenReturn(new String[] { FROM, FROM.toUpperCase() });
+
+		String destination = NotificationHelper.getNotificationDestination(mockMessage);
+
+		assertEquals(FROM, destination);
+	}
+}