Only allow new introductions in START state

When the user attempts an introduction, instead of the introduction
message input field, an explanatory text will be shown and the
introduction can not be made until the last one has been finished.

briar-android/src/main/java/org/briarproject/briar/android/introduction/IntroductionMessageFragment.java

@@ -2,6 +2,7 @@ package org.briarproject.briar.android.introduction;
 
 import android.content.Context;
 import android.os.Bundle;
+import android.support.annotation.Nullable;
 import android.support.v7.app.ActionBar;
 import android.view.LayoutInflater;
 import android.view.MenuItem;
@@ -32,6 +33,7 @@ import im.delight.android.identicons.IdenticonDrawable;
 
 import static android.app.Activity.RESULT_OK;
 import static android.view.View.GONE;
+import static android.view.View.VISIBLE;
 import static android.widget.Toast.LENGTH_SHORT;
 import static java.util.logging.Level.WARNING;
 import static org.briarproject.briar.api.introduction.IntroductionConstants.MAX_REQUEST_MESSAGE_LENGTH;
@@ -124,14 +126,15 @@ public class IntroductionMessageFragment extends BaseFragment
 						new ContactId(contactId1));
 				Contact c2 = contactManager.getContact(
 						new ContactId(contactId2));
-				setUpViews(c1, c2);
+				boolean possible = introductionManager.canIntroduce(c1, c2);
+				setUpViews(c1, c2, possible);
 			} catch (DbException e) {
 				if (LOG.isLoggable(WARNING)) LOG.log(WARNING, e.toString(), e);
 			}
 		});
 	}
 
-	private void setUpViews(Contact c1, Contact c2) {
+	private void setUpViews(Contact c1, Contact c2, boolean possible) {
 		introductionActivity.runOnUiThreadUnlessDestroyed(() -> {
 			contact1 = c1;
 			contact2 = c2;
@@ -146,13 +149,22 @@ public class IntroductionMessageFragment extends BaseFragment
 			ui.contactName1.setText(c1.getAuthor().getName());
 			ui.contactName2.setText(c2.getAuthor().getName());
 
-			// set button action
-			ui.message.setListener(IntroductionMessageFragment.this);
-
-			// hide progress bar and show views
+			// hide progress bar
 			ui.progressBar.setVisibility(GONE);
-			ui.message.setSendButtonEnabled(true);
-			ui.message.showSoftKeyboard();
+
+			if (possible) {
+				// set button action
+				ui.message.setListener(IntroductionMessageFragment.this);
+
+				// show views
+				ui.notPossible.setVisibility(GONE);
+				ui.message.setVisibility(VISIBLE);
+				ui.message.setSendButtonEnabled(true);
+				ui.message.showSoftKeyboard();
+			} else {
+				ui.notPossible.setVisibility(VISIBLE);
+				ui.message.setVisibility(GONE);
+			}
 		});
 	}
 
@@ -174,7 +186,8 @@ public class IntroductionMessageFragment extends BaseFragment
 		ui.message.setSendButtonEnabled(false);
 
 		String msg = ui.message.getText().toString();
-		msg = StringUtils.truncateUtf8(msg, MAX_REQUEST_MESSAGE_LENGTH);
+		if (msg.equals("")) msg = null;
+		else msg = StringUtils.truncateUtf8(msg, MAX_REQUEST_MESSAGE_LENGTH);
 		makeIntroduction(contact1, contact2, msg);
 
 		// don't wait for the introduction to be made before finishing activity
@@ -183,7 +196,8 @@ public class IntroductionMessageFragment extends BaseFragment
 		introductionActivity.supportFinishAfterTransition();
 	}
 
-	private void makeIntroduction(Contact c1, Contact c2, String msg) {
+	private void makeIntroduction(Contact c1, Contact c2,
+			@Nullable String msg) {
 		introductionActivity.runOnDbThread(() -> {
 			// actually make the introduction
 			try {
@@ -207,6 +221,7 @@ public class IntroductionMessageFragment extends BaseFragment
 		private final ProgressBar progressBar;
 		private final CircleImageView avatar1, avatar2;
 		private final TextView contactName1, contactName2;
+		private final TextView notPossible;
 		private final TextInputView message;
 
 		private ViewHolder(View v) {
@@ -215,6 +230,7 @@ public class IntroductionMessageFragment extends BaseFragment
 			avatar2 = v.findViewById(R.id.avatarContact2);
 			contactName1 = v.findViewById(R.id.nameContact1);
 			contactName2 = v.findViewById(R.id.nameContact2);
+			notPossible = v.findViewById(R.id.introductionNotPossibleView);
 			message = v.findViewById(R.id.introductionMessageView);
 		}
 	}

briar-android/src/main/res/layout/introduction_message.xml

@@ -94,13 +94,25 @@
 			android:layout_gravity="center"
 			tools:visibility="gone"/>
 
+		<TextView
+			android:id="@+id/introductionNotPossibleView"
+			android:layout_width="match_parent"
+			android:layout_height="wrap_content"
+			android:layout_margin="@dimen/margin_activity_horizontal"
+			android:text="@string/introduction_not_possible"
+			android:textSize="@dimen/text_size_large"
+			android:visibility="gone"
+			tools:visibility="visible"/>
+
 		<org.briarproject.briar.android.view.LargeTextInputView
 			android:id="@+id/introductionMessageView"
 			android:layout_width="match_parent"
 			android:layout_height="wrap_content"
+			android:visibility="gone"
 			app:buttonText="@string/introduction_button"
 			app:hint="@string/introduction_message_hint"
-			app:maxLines="5"/>
+			app:maxLines="5"
+			tools:visibility="visible"/>
 
 	</LinearLayout>
 </ScrollView>

briar-android/src/main/res/values/strings.xml

@@ -144,6 +144,7 @@
 	<string name="introduction_onboarding_title">Introduce your contacts</string>
 	<string name="introduction_onboarding_text">You can introduce your contacts to each other, so they don\'t need to meet in person to connect on Briar.</string>
 	<string name="introduction_activity_title">Select Contact</string>
+	<string name="introduction_not_possible">You already have one introduction in progress with these contacts. Please allow for this to finish first. If you or your contacts are rarely online, this can take some time.</string>
 	<string name="introduction_message_title">Introduce Contacts</string>
 	<string name="introduction_message_hint">Add a message (optional)</string>
 	<string name="introduction_button">Make Introduction</string>

briar-api/src/main/java/org/briarproject/briar/api/introduction/IntroductionManager.java

@@ -25,6 +25,8 @@ public interface IntroductionManager extends ConversationClient {
 	 */
 	int CLIENT_VERSION = 1;
 
+	boolean canIntroduce(Contact c1, Contact c2) throws DbException;
+
 	/**
 	 * Sends two initial introduction messages.
 	 */

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

@@ -47,6 +47,7 @@ import javax.inject.Inject;
 import static org.briarproject.bramble.api.sync.Group.Visibility.SHARED;
 import static org.briarproject.briar.api.introduction.Role.INTRODUCEE;
 import static org.briarproject.briar.api.introduction.Role.INTRODUCER;
+import static org.briarproject.briar.introduction.IntroducerState.START;
 import static org.briarproject.briar.introduction.IntroductionConstants.GROUP_KEY_CONTACT_ID;
 import static org.briarproject.briar.introduction.MessageType.ABORT;
 import static org.briarproject.briar.introduction.MessageType.ACCEPT;
@@ -267,6 +268,28 @@ class IntroductionManagerImpl extends ConversationClientImpl
 		}
 	}
 
+	@Override
+	public boolean canIntroduce(Contact c1, Contact c2) throws DbException {
+		Transaction txn = db.startTransaction(true);
+		try {
+			// Look up the session, if there is one
+			Author introducer = identityManager.getLocalAuthor(txn);
+			SessionId sessionId =
+					crypto.getSessionId(introducer, c1.getAuthor(),
+							c2.getAuthor());
+			StoredSession ss = getSession(txn, sessionId);
+			if (ss == null) return true;
+			IntroducerSession session =
+					sessionParser.parseIntroducerSession(ss.bdfSession);
+			if (session.getState() == START) return true;
+		} catch (FormatException e) {
+			throw new DbException(e);
+		} finally {
+			db.endTransaction(txn);
+		}
+		return false;
+	}
+
 	@Override
 	public void makeIntroduction(Contact c1, Contact c2, @Nullable String msg,
 			long timestamp) throws DbException {
@@ -398,12 +421,11 @@ class IntroductionManagerImpl extends ConversationClientImpl
 		Role role = sessionParser.getRole(bdfSession);
 		SessionId sessionId;
 		Author author;
-		LocalAuthor localAuthor = identityManager.getLocalAuthor(txn);
 		if (role == INTRODUCER) {
 			IntroducerSession session =
 					sessionParser.parseIntroducerSession(bdfSession);
 			sessionId = session.getSessionId();
-			if (localAuthor.equals(session.getIntroducee1().author)) {
+			if (contactGroupId.equals(session.getIntroducee1().groupId)) {
 				author = session.getIntroducee2().author;
 			} else {
 				author = session.getIntroducee1().author;
@@ -419,6 +441,7 @@ class IntroductionManagerImpl extends ConversationClientImpl
 		if (msg == null || body == null) throw new AssertionError();
 		RequestMessage rm = messageParser.parseRequestMessage(msg, body);
 		String message = rm.getMessage();
+		LocalAuthor localAuthor = identityManager.getLocalAuthor(txn);
 		boolean contactExists = contactManager
 				.contactExists(txn, rm.getAuthor().getId(),
 						localAuthor.getId());

briar-core/src/test/java/org/briarproject/briar/introduction/IntroductionIntegrationTest.java

@@ -23,6 +23,7 @@ import org.briarproject.bramble.api.sync.Group;
 import org.briarproject.bramble.api.sync.Message;
 import org.briarproject.bramble.api.sync.MessageId;
 import org.briarproject.bramble.test.TestDatabaseModule;
+import org.briarproject.briar.api.client.ProtocolStateException;
 import org.briarproject.briar.api.client.SessionId;
 import org.briarproject.briar.api.introduction.IntroductionManager;
 import org.briarproject.briar.api.introduction.IntroductionMessage;
@@ -446,6 +447,26 @@ public class IntroductionIntegrationTest
 		assertFalse(listener2.aborted);
 	}
 
+	@Test(expected = ProtocolStateException.class)
+	public void testDoubleIntroduction() throws Exception {
+		// we can make an introduction
+		assertTrue(introductionManager0
+				.canIntroduce(contact1From0, contact2From0));
+
+		// make the introduction
+		long time = clock.currentTimeMillis();
+		introductionManager0
+				.makeIntroduction(contact1From0, contact2From0, null, time);
+
+		// no more introduction allowed while the existing one is in progress
+		assertFalse(introductionManager0
+				.canIntroduce(contact1From0, contact2From0));
+
+		// try it anyway and fail
+		introductionManager0
+				.makeIntroduction(contact1From0, contact2From0, null, time);
+	}
+
 	@Test
 	public void testIntroducerRemovedCleanup() throws Exception {
 		addListeners(true, true);