This addresses two types of introduction corner cases:

* force decline when two of our own identities are introduced to each
  other
* throw away introduction requests to the same identity
  (impossible to trigger from UI)

Closes #284

briar-android/res/layout/list_item_introduction_in.xml

@@ -36,7 +36,7 @@
 			android:layout_marginTop="@dimen/message_bubble_timestamp_margin"
 			android:layout_alignEnd="@+id/introductionText"
 			android:layout_alignRight="@+id/introductionText"
-			android:layout_below="@+id/acceptButton"
+			android:layout_below="@+id/declineButton"
 			android:textColor="@color/private_message_date"
 			android:textSize="@dimen/text_size_tiny"
 			tools:text="Dec 24, 13:37"/>
@@ -46,7 +46,6 @@
 			style="@style/BriarButtonFlat.Positive"
 			android:layout_width="wrap_content"
 			android:layout_height="wrap_content"
-			android:layout_marginBottom="-15dp"
 			android:layout_alignEnd="@+id/introductionText"
 			android:layout_alignRight="@+id/introductionText"
 			android:layout_below="@+id/introductionText"
@@ -57,6 +56,7 @@
 			style="@style/BriarButtonFlat.Negative"
 			android:layout_width="wrap_content"
 			android:layout_height="wrap_content"
+			android:layout_marginBottom="-15dp"
 			android:layout_below="@+id/introductionText"
 			android:layout_toLeftOf="@+id/acceptButton"
 			android:layout_toStartOf="@+id/acceptButton"

briar-android/res/values/strings.xml

@@ -155,6 +155,7 @@
 	<string name="introduction_request_sent">You have asked to introduce %1$s to %2$s.</string>
 	<string name="introduction_request_received">%1$s has asked to introduce you to %2$s. Do you want to add %2$s to your contact list?</string>
 	<string name="introduction_request_exists_received">%1$s has asked to introduce you to %2$s, but %2$s is already in your contact list. Since %1$s might not know that, you can still respond:</string>
+	<string name="introduction_request_for_our_identity_received">%1$s has asked to introduce you to %2$s, but %2$s is one of your other identities. For that reason you cannot accept the introduction:</string>
 	<string name="introduction_request_answered_received">%1$s has asked to introduce you to %2$s.</string>
 	<string name="introduction_response_accepted_sent">You accepted the introduction to %1$s.</string>
 	<string name="introduction_response_declined_sent">You declined the introduction to %1$s.</string>

briar-android/src/org/briarproject/android/contact/ConversationAdapter.java

@@ -261,15 +261,23 @@ class ConversationAdapter extends RecyclerView.Adapter {
 								contactName, ir.getName()));
 			}
 
-			ui.acceptButton.setVisibility(View.VISIBLE);
-			ui.acceptButton.setOnClickListener(new View.OnClickListener() {
-				@Override
-				public void onClick(View v) {
-					intro.respondToIntroduction(ir.getSessionId(), true);
-					item.setAnswered(true);
-					notifyItemChanged(position);
-				}
-			});
+			if (item.getIntroductionRequest().doesIntroduceOtherIdentity()) {
+				// don't allow accept when one of our identities is introduced
+				ui.acceptButton.setVisibility(View.GONE);
+				ui.text.setText(ctx.getString(
+						R.string.introduction_request_for_our_identity_received,
+						contactName, ir.getName()));
+			} else {
+				ui.acceptButton.setVisibility(View.VISIBLE);
+				ui.acceptButton.setOnClickListener(new View.OnClickListener() {
+					@Override
+					public void onClick(View v) {
+						intro.respondToIntroduction(ir.getSessionId(), true);
+						item.setAnswered(true);
+						notifyItemChanged(position);
+					}
+				});
+			}
 			ui.declineButton.setVisibility(View.VISIBLE);
 			ui.declineButton.setOnClickListener(new View.OnClickListener() {
 				@Override

briar-api/src/org/briarproject/api/db/DatabaseComponent.java

@@ -102,6 +102,12 @@ public interface DatabaseComponent {
 	 */
 	boolean containsGroup(Transaction txn, GroupId g) throws DbException;
 
+	/**
+	 * Returns true if the database contains the given local author.
+	 */
+	boolean containsLocalAuthor(Transaction txn, AuthorId local)
+			throws DbException;
+
 	/**
 	 * Deletes the message with the given ID. The message ID and any other
 	 * associated data are not deleted.

briar-api/src/org/briarproject/api/introduction/IntroductionConstants.java

@@ -57,6 +57,7 @@ public interface IntroductionConstants {
 	String ADDED_CONTACT_ID = "addedContactId";
 	String NOT_OUR_RESPONSE = "notOurResponse";
 	String EXISTS = "contactExists";
+	String REMOTE_AUTHOR_IS_US = "remoteAuthorIsUs";
 	String ANSWERED = "answered";
 
 	String TASK = "task";

briar-api/src/org/briarproject/api/introduction/IntroductionRequest.java

@@ -6,12 +6,12 @@ import org.briarproject.api.sync.MessageId;
 public class IntroductionRequest extends IntroductionResponse {
 
 	private final String message;
-	private final boolean answered, exists;
+	private final boolean answered, exists, introducesOtherIdentity;
 
 	public IntroductionRequest(SessionId sessionId, MessageId messageId,
 			long time, boolean local, boolean sent, boolean seen, boolean read,
 			AuthorId authorId, String name, boolean accepted, String message,
-			boolean answered, boolean exists) {
+			boolean answered, boolean exists, boolean introducesOtherIdentity) {
 
 		super(sessionId, messageId, time, local, sent, seen, read, authorId,
 				name, accepted);
@@ -19,6 +19,7 @@ public class IntroductionRequest extends IntroductionResponse {
 		this.message = message;
 		this.answered = answered;
 		this.exists = exists;
+		this.introducesOtherIdentity = introducesOtherIdentity;
 	}
 
 	public String getMessage() {
@@ -33,4 +34,7 @@ public class IntroductionRequest extends IntroductionResponse {
 		return exists;
 	}
 
+	public boolean doesIntroduceOtherIdentity() {
+		return introducesOtherIdentity;
+	}
 }

briar-core/src/org/briarproject/db/DatabaseComponentImpl.java

@@ -243,6 +243,13 @@ class DatabaseComponentImpl<T> implements DatabaseComponent {
 		return db.containsGroup(txn, g);
 	}
 
+	@Override
+	public boolean containsLocalAuthor(Transaction transaction, AuthorId local)
+			throws DbException {
+		T txn = unbox(transaction);
+		return db.containsLocalAuthor(txn, local);
+	}
+
 	public void deleteMessage(Transaction transaction, MessageId m)
 			throws DbException {
 		if (transaction.isReadOnly()) throw new IllegalArgumentException();

briar-core/src/org/briarproject/introduction/IntroduceeEngine.java

@@ -47,6 +47,7 @@ import static org.briarproject.api.introduction.IntroductionConstants.OUR_PUBLIC
 import static org.briarproject.api.introduction.IntroductionConstants.OUR_TIME;
 import static org.briarproject.api.introduction.IntroductionConstants.PUBLIC_KEY;
 import static org.briarproject.api.introduction.IntroductionConstants.REMOTE_AUTHOR_ID;
+import static org.briarproject.api.introduction.IntroductionConstants.REMOTE_AUTHOR_IS_US;
 import static org.briarproject.api.introduction.IntroductionConstants.SESSION_ID;
 import static org.briarproject.api.introduction.IntroductionConstants.STATE;
 import static org.briarproject.api.introduction.IntroductionConstants.TASK;
@@ -328,10 +329,12 @@ public class IntroduceeEngine
 		String name = msg.getString(NAME);
 		String message = msg.getOptionalString(MSG);
 		boolean exists = localState.getBoolean(EXISTS);
+		boolean introducesOtherIdentity =
+				localState.getBoolean(REMOTE_AUTHOR_IS_US);
 
 		IntroductionRequest ir = new IntroductionRequest(sessionId, messageId,
 				time, false, false, false, false, authorId, name, false,
-				message, false, exists);
+				message, false, exists, introducesOtherIdentity);
 		return new IntroductionRequestReceivedEvent(contactId, ir);
 	}
 

briar-core/src/org/briarproject/introduction/IntroduceeManager.java

@@ -59,6 +59,7 @@ import static org.briarproject.api.introduction.IntroductionConstants.OUR_PUBLIC
 import static org.briarproject.api.introduction.IntroductionConstants.OUR_TIME;
 import static org.briarproject.api.introduction.IntroductionConstants.PUBLIC_KEY;
 import static org.briarproject.api.introduction.IntroductionConstants.REMOTE_AUTHOR_ID;
+import static org.briarproject.api.introduction.IntroductionConstants.REMOTE_AUTHOR_IS_US;
 import static org.briarproject.api.introduction.IntroductionConstants.ROLE;
 import static org.briarproject.api.introduction.IntroductionConstants.ROLE_INTRODUCEE;
 import static org.briarproject.api.introduction.IntroductionConstants.STATE;
@@ -147,6 +148,17 @@ class IntroduceeManager {
 		d.put(EXISTS, exists);
 		d.put(REMOTE_AUTHOR_ID, remoteAuthorId);
 
+		// check if someone is trying to introduce us to ourselves
+		if(remoteAuthorId.equals(introducer.getLocalAuthorId())) {
+			LOG.warning("Received Introduction Request to Ourselves");
+			throw new FormatException();
+		}
+
+		// check if remote author is actually one of our other identities
+		boolean introducesOtherIdentity =
+				db.containsLocalAuthor(txn, remoteAuthorId);
+		d.put(REMOTE_AUTHOR_IS_US, introducesOtherIdentity);
+
 		// save local state to database
 		clientHelper.addLocalMessage(txn, localMsg,
 				IntroductionManagerImpl.CLIENT_ID, d, false);

briar-core/src/org/briarproject/introduction/IntroductionManagerImpl.java

@@ -60,6 +60,7 @@ import static org.briarproject.api.introduction.IntroductionConstants.NAME;
 import static org.briarproject.api.introduction.IntroductionConstants.NOT_OUR_RESPONSE;
 import static org.briarproject.api.introduction.IntroductionConstants.READ;
 import static org.briarproject.api.introduction.IntroductionConstants.REMOTE_AUTHOR_ID;
+import static org.briarproject.api.introduction.IntroductionConstants.REMOTE_AUTHOR_IS_US;
 import static org.briarproject.api.introduction.IntroductionConstants.RESPONSE_1;
 import static org.briarproject.api.introduction.IntroductionConstants.RESPONSE_2;
 import static org.briarproject.api.introduction.IntroductionConstants.ROLE;
@@ -186,9 +187,11 @@ class IntroductionManagerImpl extends BdfIncomingMessageHook
 				state = introduceeManager.initialize(txn, groupId, message);
 			} catch (FormatException e) {
 				if (LOG.isLoggable(WARNING)) {
-					LOG.warning("Could not initialize introducee state");
+					LOG.warning(
+							"Could not initialize introducee state, deleting...");
 					LOG.log(WARNING, e.toString(), e);
 				}
+				deleteMessage(txn, m.getId());
 				return;
 			}
 			try {
@@ -361,7 +364,7 @@ class IntroductionManagerImpl extends BdfIncomingMessageHook
 						list.add(ir);
 					} else if (type == TYPE_REQUEST) {
 						String message;
-						boolean answered, exists;
+						boolean answered, exists, introducesOtherIdentity;
 						if (state.getLong(ROLE) == ROLE_INTRODUCER) {
 							local = true;
 							authorId =
@@ -370,6 +373,7 @@ class IntroductionManagerImpl extends BdfIncomingMessageHook
 							message = msg.getOptionalString(MSG);
 							answered = false;
 							exists = false;
+							introducesOtherIdentity = false;
 						} else {
 							local = false;
 							authorId = new AuthorId(
@@ -378,11 +382,14 @@ class IntroductionManagerImpl extends BdfIncomingMessageHook
 							message = state.getOptionalString(MSG);
 							answered = state.getBoolean(ANSWERED);
 							exists = state.getBoolean(EXISTS);
+							introducesOtherIdentity =
+									state.getBoolean(REMOTE_AUTHOR_IS_US);
 						}
 						IntroductionRequest ir = new IntroductionRequest(
 								sessionId, messageId, time, local, s.isSent(),
 								s.isSeen(), read, authorId, name, accepted,
-								message, answered, exists);
+								message, answered, exists,
+								introducesOtherIdentity);
 						list.add(ir);
 					}
 				} catch (FormatException e) {

briar-tests/src/org/briarproject/introduction/IntroduceeManagerTest.java

@@ -51,6 +51,7 @@ import static org.briarproject.api.introduction.IntroductionConstants.NAME;
 import static org.briarproject.api.introduction.IntroductionConstants.NOT_OUR_RESPONSE;
 import static org.briarproject.api.introduction.IntroductionConstants.PUBLIC_KEY;
 import static org.briarproject.api.introduction.IntroductionConstants.REMOTE_AUTHOR_ID;
+import static org.briarproject.api.introduction.IntroductionConstants.REMOTE_AUTHOR_IS_US;
 import static org.briarproject.api.introduction.IntroductionConstants.ROLE;
 import static org.briarproject.api.introduction.IntroductionConstants.ROLE_INTRODUCEE;
 import static org.briarproject.api.introduction.IntroductionConstants.SESSION_ID;
@@ -239,6 +240,7 @@ public class IntroduceeManagerTest extends BriarTestCase {
 		state.put(ANSWERED, false);
 		state.put(EXISTS, true);
 		state.put(REMOTE_AUTHOR_ID, introducee2.getAuthor().getId());
+		state.put(REMOTE_AUTHOR_IS_US, false);
 
 		context.checking(new Expectations() {{
 			oneOf(clock).currentTimeMillis();
@@ -268,6 +270,10 @@ public class IntroduceeManagerTest extends BriarTestCase {
 							introducer.getLocalAuthorId());
 			will(returnValue(contactExists));
 
+			// checks if remote author is one of our identities
+			oneOf(db).containsLocalAuthor(txn, introducee2.getAuthor().getId());
+			will(returnValue(false));
+
 			// store session state
 			oneOf(clientHelper)
 					.addLocalMessage(txn, localStateMessage, clientId, state,