Add the ability to block groups.

This also fixes the situation where we block group-leave messages,
preventing blocked contacts from leaving groups.

Fixes #7970

Also, this forced us to upgrade libsignal-service, which fixes the
websocket timeout issues. Thanks to @dpapavas!

Fixes #6644

src/org/thoughtcrime/securesms/ConversationActivity.java

@@ -51,6 +51,8 @@ import android.support.v7.app.AlertDialog;
 import android.text.Editable;
 import android.text.TextUtils;
 import android.text.TextWatcher;
+
+import org.thoughtcrime.securesms.database.GroupDatabase;
 import org.thoughtcrime.securesms.logging.Log;
 import android.util.Pair;
 import android.view.KeyEvent;
@@ -70,7 +72,6 @@ import android.widget.TextView;
 import android.widget.Toast;
 
 import com.google.android.gms.location.places.ui.PlacePicker;
-import com.google.protobuf.ByteString;
 
 import org.greenrobot.eventbus.EventBus;
 import org.greenrobot.eventbus.Subscribe;
@@ -192,7 +193,6 @@ import java.util.concurrent.atomic.AtomicInteger;
 import static org.thoughtcrime.securesms.TransportOption.Type;
 import static org.thoughtcrime.securesms.database.GroupDatabase.GroupRecord;
 import static org.whispersystems.libsignal.SessionCipher.SESSION_LOCK;
-import static org.whispersystems.signalservice.internal.push.SignalServiceProtos.GroupContext;
 
 /**
  * Activity for displaying a message thread, as well as
@@ -693,26 +693,34 @@ public class ConversationActivity extends PassphraseRequiredActionBarActivity
   }
 
   private void handleUnblock() {
+    int titleRes = R.string.ConversationActivity_unblock_this_contact_question;
+    int bodyRes  = R.string.ConversationActivity_you_will_once_again_be_able_to_receive_messages_and_calls_from_this_contact;
+
+    if (recipient.isGroupRecipient()) {
+      titleRes = R.string.ConversationActivity_unblock_this_group_question;
+      bodyRes  = R.string.ConversationActivity_unblock_this_group_description;
+    }
+
     //noinspection CodeBlock2Expr
     new AlertDialog.Builder(this)
-        .setTitle(R.string.ConversationActivity_unblock_this_contact_question)
-        .setMessage(R.string.ConversationActivity_you_will_once_again_be_able_to_receive_messages_and_calls_from_this_contact)
-        .setNegativeButton(android.R.string.cancel, null)
-        .setPositiveButton(R.string.ConversationActivity_unblock, (dialog, which) -> {
-          new AsyncTask<Void, Void, Void>() {
-            @Override
-            protected Void doInBackground(Void... params) {
-              DatabaseFactory.getRecipientDatabase(ConversationActivity.this)
+                   .setTitle(titleRes)
+                   .setMessage(bodyRes)
+                   .setNegativeButton(android.R.string.cancel, null)
+                   .setPositiveButton(R.string.ConversationActivity_unblock, (dialog, which) -> {
+                     new AsyncTask<Void, Void, Void>() {
+                       @Override
+                       protected Void doInBackground(Void... params) {
+                         DatabaseFactory.getRecipientDatabase(ConversationActivity.this)
                              .setBlocked(recipient, false);
 
-              ApplicationContext.getInstance(ConversationActivity.this)
-                                .getJobManager()
-                                .add(new MultiDeviceBlockedUpdateJob(ConversationActivity.this));
+                         ApplicationContext.getInstance(ConversationActivity.this)
+                             .getJobManager()
+                             .add(new MultiDeviceBlockedUpdateJob(ConversationActivity.this));
 
-              return null;
-            }
-          }.executeOnExecutor(AsyncTask.THREAD_POOL_EXECUTOR);
-        }).show();
+                         return null;
+                       }
+                     }.executeOnExecutor(AsyncTask.THREAD_POOL_EXECUTOR);
+                   }).show();
   }
 
   @TargetApi(Build.VERSION_CODES.KITKAT)
@@ -847,24 +855,21 @@ public class ConversationActivity extends PassphraseRequiredActionBarActivity
     builder.setCancelable(true);
     builder.setMessage(getString(R.string.ConversationActivity_are_you_sure_you_want_to_leave_this_group));
     builder.setPositiveButton(R.string.yes, (dialog, which) -> {
-      Context self = ConversationActivity.this;
+      Recipient                           groupRecipient = getRecipient();
+      long                                threadId       = DatabaseFactory.getThreadDatabase(this).getThreadIdFor(groupRecipient);
+      Optional<OutgoingGroupMediaMessage> leaveMessage   = GroupUtil.createGroupLeaveMessage(this, groupRecipient);
 
-      try {
-        String groupId = getRecipient().getAddress().toGroupString();
-        DatabaseFactory.getGroupDatabase(self).setActive(groupId, false);
+      if (threadId != -1 && leaveMessage.isPresent()) {
+        MessageSender.send(this, leaveMessage.get(), threadId, false, null);
 
-        GroupContext context = GroupContext.newBuilder()
-                                           .setId(ByteString.copyFrom(GroupUtil.getDecodedId(groupId)))
-                                           .setType(GroupContext.Type.QUIT)
-                                           .build();
+        GroupDatabase groupDatabase = DatabaseFactory.getGroupDatabase(this);
+        String        groupId       = groupRecipient.getAddress().toGroupString();
+        groupDatabase.setActive(groupId, false);
+        groupDatabase.remove(groupId, Address.fromSerialized(TextSecurePreferences.getLocalNumber(this)));
 
-        OutgoingGroupMediaMessage outgoingMessage = new OutgoingGroupMediaMessage(getRecipient(), context, null, System.currentTimeMillis(), 0, null, Collections.emptyList());
-        MessageSender.send(self, outgoingMessage, threadId, false, null);
-        DatabaseFactory.getGroupDatabase(self).remove(groupId, Address.fromSerialized(TextSecurePreferences.getLocalNumber(self)));
         initializeEnabledCheck();
-      } catch (IOException e) {
-        Log.w(TAG, e);
-        Toast.makeText(self, R.string.ConversationActivity_error_leaving_group, Toast.LENGTH_LONG).show();
+      } else {
+        Toast.makeText(this, R.string.ConversationActivity_error_leaving_group, Toast.LENGTH_LONG).show();
       }
     });
 

src/org/thoughtcrime/securesms/RecipientPreferenceActivity.java

@@ -3,7 +3,6 @@ package org.thoughtcrime.securesms;
 import android.annotation.SuppressLint;
 import android.content.ActivityNotFoundException;
 import android.content.Context;
-import android.content.DialogInterface;
 import android.content.Intent;
 import android.database.Cursor;
 import android.graphics.Color;
@@ -30,6 +29,7 @@ import android.support.v7.widget.Toolbar;
 import android.telephony.PhoneNumberUtils;
 
 import org.thoughtcrime.securesms.components.SwitchPreferenceCompat;
+import org.thoughtcrime.securesms.database.GroupDatabase;
 import org.thoughtcrime.securesms.logging.Log;
 import android.util.Pair;
 import android.view.MenuItem;
@@ -37,6 +37,7 @@ import android.view.View;
 import android.view.WindowManager;
 import android.widget.ImageView;
 import android.widget.TextView;
+import android.widget.Toast;
 
 import com.bumptech.glide.load.engine.DiskCacheStrategy;
 
@@ -55,6 +56,7 @@ import org.thoughtcrime.securesms.jobs.MultiDeviceBlockedUpdateJob;
 import org.thoughtcrime.securesms.jobs.MultiDeviceContactUpdateJob;
 import org.thoughtcrime.securesms.mms.GlideApp;
 import org.thoughtcrime.securesms.mms.GlideRequests;
+import org.thoughtcrime.securesms.mms.OutgoingGroupMediaMessage;
 import org.thoughtcrime.securesms.notifications.NotificationChannels;
 import org.thoughtcrime.securesms.permissions.Permissions;
 import org.thoughtcrime.securesms.preferences.CorrectedPreferenceFragment;
@@ -62,11 +64,13 @@ import org.thoughtcrime.securesms.preferences.widgets.ColorPickerPreference;
 import org.thoughtcrime.securesms.preferences.widgets.ContactPreference;
 import org.thoughtcrime.securesms.recipients.Recipient;
 import org.thoughtcrime.securesms.recipients.RecipientModifiedListener;
+import org.thoughtcrime.securesms.sms.MessageSender;
 import org.thoughtcrime.securesms.util.CommunicationActions;
 import org.thoughtcrime.securesms.util.Dialogs;
 import org.thoughtcrime.securesms.util.DynamicLanguage;
 import org.thoughtcrime.securesms.util.DynamicNoActionBarTheme;
 import org.thoughtcrime.securesms.util.DynamicTheme;
+import org.thoughtcrime.securesms.util.GroupUtil;
 import org.thoughtcrime.securesms.util.IdentityUtil;
 import org.thoughtcrime.securesms.util.TextSecurePreferences;
 import org.thoughtcrime.securesms.util.Util;
@@ -378,10 +382,7 @@ public class RecipientPreferenceActivity extends PassphraseRequiredActionBarActi
 
       if (recipient.isGroupRecipient()) {
         if (colorPreference    != null) colorPreference.setVisible(false);
-        if (blockPreference    != null) blockPreference.setVisible(false);
         if (identityPreference != null) identityPreference.setVisible(false);
-        if (privacyCategory    != null) privacyCategory.setVisible(false);
-        if (divider            != null) divider.setVisible(false);
         if (aboutCategory      != null) getPreferenceScreen().removePreference(aboutCategory);
         if (aboutDivider       != null) getPreferenceScreen().removePreference(aboutDivider);
       } else {
@@ -659,31 +660,55 @@ public class RecipientPreferenceActivity extends PassphraseRequiredActionBarActi
       }
 
       private void handleBlock() {
-        new AlertDialog.Builder(getActivity())
-            .setTitle(R.string.RecipientPreferenceActivity_block_this_contact_question)
-            .setMessage(R.string.RecipientPreferenceActivity_you_will_no_longer_receive_messages_and_calls_from_this_contact)
-            .setCancelable(true)
-            .setNegativeButton(android.R.string.cancel, null)
-            .setPositiveButton(R.string.RecipientPreferenceActivity_block, new DialogInterface.OnClickListener() {
-              @Override
-              public void onClick(DialogInterface dialog, int which) {
-                setBlocked(recipient, true);
+        new AsyncTask<Void, Void, Pair<Integer, Integer>>() {
+
+          @Override
+          protected Pair<Integer, Integer> doInBackground(Void... voids) {
+            int titleRes = R.string.RecipientPreferenceActivity_block_this_contact_question;
+            int bodyRes  = R.string.RecipientPreferenceActivity_you_will_no_longer_receive_messages_and_calls_from_this_contact;
+
+            if (recipient.isGroupRecipient()) {
+              bodyRes = R.string.RecipientPreferenceActivity_block_and_leave_group_description;
+
+              if (recipient.isGroupRecipient() && DatabaseFactory.getGroupDatabase(getContext()).isActive(recipient.getAddress().toGroupString())) {
+                titleRes = R.string.RecipientPreferenceActivity_block_and_leave_group;
+              } else {
+                titleRes = R.string.RecipientPreferenceActivity_block_group;
               }
-            }).show();
+            }
+
+            return new Pair<>(titleRes, bodyRes);
+          }
+
+          @Override
+          protected void onPostExecute(Pair<Integer, Integer> titleAndBody) {
+            new AlertDialog.Builder(getActivity())
+                           .setTitle(titleAndBody.first)
+                           .setMessage(titleAndBody.second)
+                           .setCancelable(true)
+                           .setNegativeButton(android.R.string.cancel, null)
+                           .setPositiveButton(R.string.RecipientPreferenceActivity_block, (dialog, which) -> {
+                             setBlocked(recipient, true);
+                           }).show();
+          }
+        }.execute();
       }
 
       private void handleUnblock() {
+        int titleRes = R.string.RecipientPreferenceActivity_unblock_this_contact_question;
+        int bodyRes  = R.string.RecipientPreferenceActivity_you_will_once_again_be_able_to_receive_messages_and_calls_from_this_contact;
+
+        if (recipient.isGroupRecipient()) {
+          titleRes = R.string.RecipientPreferenceActivity_unblock_this_group_question;
+          bodyRes  = R.string.RecipientPreferenceActivity_unblock_this_group_description;
+        }
+
         new AlertDialog.Builder(getActivity())
-            .setTitle(R.string.RecipientPreferenceActivity_unblock_this_contact_question)
-            .setMessage(R.string.RecipientPreferenceActivity_you_will_once_again_be_able_to_receive_messages_and_calls_from_this_contact)
-            .setCancelable(true)
-            .setNegativeButton(android.R.string.cancel, null)
-            .setPositiveButton(R.string.RecipientPreferenceActivity_unblock, new DialogInterface.OnClickListener() {
-              @Override
-              public void onClick(DialogInterface dialog, int which) {
-                setBlocked(recipient, false);
-              }
-            }).show();
+                       .setTitle(titleRes)
+                       .setMessage(bodyRes)
+                       .setCancelable(true)
+                       .setNegativeButton(android.R.string.cancel, null)
+                       .setPositiveButton(R.string.RecipientPreferenceActivity_unblock, (dialog, which) -> setBlocked(recipient, false)).show();
       }
 
       private void setBlocked(final Recipient recipient, final boolean blocked) {
@@ -695,6 +720,23 @@ public class RecipientPreferenceActivity extends PassphraseRequiredActionBarActi
             DatabaseFactory.getRecipientDatabase(context)
                            .setBlocked(recipient, blocked);
 
+            if (recipient.isGroupRecipient() && DatabaseFactory.getGroupDatabase(context).isActive(recipient.getAddress().toGroupString())) {
+              long                                threadId     = DatabaseFactory.getThreadDatabase(context).getThreadIdFor(recipient);
+              Optional<OutgoingGroupMediaMessage> leaveMessage = GroupUtil.createGroupLeaveMessage(context, recipient);
+
+              if (threadId != -1 && leaveMessage.isPresent()) {
+                MessageSender.send(context, leaveMessage.get(), threadId, false, null);
+
+                GroupDatabase groupDatabase = DatabaseFactory.getGroupDatabase(context);
+                String        groupId       = recipient.getAddress().toGroupString();
+                groupDatabase.setActive(groupId, false);
+                groupDatabase.remove(groupId, Address.fromSerialized(TextSecurePreferences.getLocalNumber(context)));
+              } else {
+                Log.w(TAG, "Failed to leave group. Can't block.");
+                Toast.makeText(context, R.string.RecipientPreferenceActivity_error_leaving_group, Toast.LENGTH_LONG).show();
+              }
+            }
+
             ApplicationContext.getInstance(context)
                               .getJobManager()
                               .add(new MultiDeviceBlockedUpdateJob(context));

src/org/thoughtcrime/securesms/dependencies/SignalCommunicationModule.java

@@ -44,6 +44,9 @@ import org.whispersystems.signalservice.api.SignalServiceAccountManager;
 import org.whispersystems.signalservice.api.SignalServiceMessageReceiver;
 import org.whispersystems.signalservice.api.SignalServiceMessageSender;
 import org.whispersystems.signalservice.api.util.CredentialsProvider;
+import org.whispersystems.signalservice.api.util.RealtimeSleepTimer;
+import org.whispersystems.signalservice.api.util.SleepTimer;
+import org.whispersystems.signalservice.api.util.UptimeSleepTimer;
 import org.whispersystems.signalservice.api.websocket.ConnectivityListener;
 
 import dagger.Module;
@@ -124,10 +127,13 @@ public class SignalCommunicationModule {
   @Provides
   synchronized SignalServiceMessageReceiver provideSignalMessageReceiver() {
     if (this.messageReceiver == null) {
+      SleepTimer sleepTimer =  TextSecurePreferences.isGcmDisabled(context) ? new RealtimeSleepTimer(context) : new UptimeSleepTimer();
+
       this.messageReceiver = new SignalServiceMessageReceiver(networkAccess.getConfiguration(context),
                                                               new DynamicCredentialsProvider(context),
                                                               BuildConfig.USER_AGENT,
-                                                              new PipeConnectivityListener());
+                                                              new PipeConnectivityListener(),
+                                                              sleepTimer);
     }
 
     return this.messageReceiver;

src/org/thoughtcrime/securesms/jobs/MultiDeviceBlockedUpdateJob.java

@@ -11,6 +11,7 @@ import org.thoughtcrime.securesms.jobmanager.JobParameters;
 import org.thoughtcrime.securesms.jobmanager.requirements.NetworkRequirement;
 import org.thoughtcrime.securesms.jobs.requirements.MasterSecretRequirement;
 import org.thoughtcrime.securesms.recipients.Recipient;
+import org.thoughtcrime.securesms.util.GroupUtil;
 import org.whispersystems.signalservice.api.SignalServiceMessageSender;
 import org.whispersystems.signalservice.api.crypto.UntrustedIdentityException;
 import org.whispersystems.signalservice.api.messages.multidevice.BlockedListMessage;
@@ -47,17 +48,20 @@ public class MultiDeviceBlockedUpdateJob extends MasterSecretJob implements Inje
     RecipientDatabase database = DatabaseFactory.getRecipientDatabase(context);
 
     try (RecipientReader reader = database.readerForBlocked(database.getBlocked())) {
-      List<String> blocked = new LinkedList<>();
+      List<String> blockedIndividuals = new LinkedList<>();
+      List<byte[]> blockedGroups      = new LinkedList<>();
 
       Recipient recipient;
 
       while ((recipient = reader.getNext()) != null) {
-        if (!recipient.isGroupRecipient()) {
-          blocked.add(recipient.getAddress().serialize());
+        if (recipient.isGroupRecipient()) {
+          blockedGroups.add(GroupUtil.getDecodedId(recipient.getAddress().toGroupString()));
+        } else {
+          blockedIndividuals.add(recipient.getAddress().serialize());
         }
       }
 
-      messageSender.sendMessage(SignalServiceSyncMessage.forBlocked(new BlockedListMessage(blocked)));
+      messageSender.sendMessage(SignalServiceSyncMessage.forBlocked(new BlockedListMessage(blockedIndividuals, blockedGroups)));
     }
   }
 

src/org/thoughtcrime/securesms/jobs/MultiDeviceGroupUpdateJob.java

@@ -75,7 +75,9 @@ public class MultiDeviceGroupUpdateJob extends MasterSecretJob implements Inject
 
           out.write(new DeviceGroup(record.getId(), Optional.fromNullable(record.getTitle()),
                                     members, getAvatar(record.getAvatar()),
-                                    record.isActive(), expirationTimer));
+                                    record.isActive(), expirationTimer,
+                                    Optional.of(recipient.getColor().serialize()),
+                                    recipient.isBlocked()));
         }
       }
 

src/org/thoughtcrime/securesms/jobs/PushDecryptJob.java

@@ -175,6 +175,11 @@ public class PushDecryptJob extends ContextJob {
 
       SignalServiceContent content = cipher.decrypt(envelope);
 
+      if (shouldIgnore(envelope, content)) {
+        Log.i(TAG, "Ignoring message.");
+        return;
+      }
+
       if (content.getDataMessage().isPresent()) {
         SignalServiceDataMessage message        = content.getDataMessage().get();
         boolean                  isMediaMessage = message.getAttachments().isPresent() || message.getQuote().isPresent() || message.getSharedContacts().isPresent();
@@ -941,4 +946,36 @@ public class PushDecryptJob extends ContextJob {
       return Recipient.from(context, Address.fromExternal(context, envelope.getSource()), false);
     }
   }
+
+  private boolean shouldIgnore(@NonNull SignalServiceEnvelope envelope, @NonNull SignalServiceContent content) {
+    Recipient sender = Recipient.from(context, Address.fromExternal(context, envelope.getSource()), false);
+
+    if (content.getDataMessage().isPresent()) {
+      SignalServiceDataMessage message      = content.getDataMessage().get();
+      Recipient                conversation = getMessageDestination(envelope, message);
+
+      if (conversation.isGroupRecipient() && conversation.isBlocked()) {
+        return true;
+      } else if (conversation.isGroupRecipient()) {
+        GroupDatabase    groupDatabase = DatabaseFactory.getGroupDatabase(context);
+        Optional<String> groupId       = message.getGroupInfo().isPresent() ? Optional.of(GroupUtil.getEncodedId(message.getGroupInfo().get().getGroupId(), false))
+                                                                            : Optional.absent();
+
+        boolean isTextMessage    = message.getBody().isPresent();
+        boolean isMediaMessage   = message.getAttachments().isPresent() || message.getQuote().isPresent() || message.getSharedContacts().isPresent();
+        boolean isExpireMessage  = message.isExpirationUpdate();
+        boolean isContentMessage = !message.isGroupUpdate() && (isTextMessage || isMediaMessage || isExpireMessage);
+        boolean isGroupActive    = groupId.isPresent() && groupDatabase.isActive(groupId.get());
+        boolean isLeaveMessage   = message.getGroupInfo().isPresent() && message.getGroupInfo().get().getType() == SignalServiceGroup.Type.QUIT;
+
+        return (isContentMessage && !isGroupActive) || (sender.isBlocked() && !isLeaveMessage);
+      } else {
+        return sender.isBlocked();
+      }
+    } else if (content.getCallMessage().isPresent()) {
+      return sender.isBlocked();
+    }
+
+    return false;
+  }
 }

src/org/thoughtcrime/securesms/jobs/PushReceivedJob.java

@@ -34,22 +34,17 @@ public abstract class PushReceivedJob extends ContextJob {
     if (envelope.isReceipt()) {
       handleReceipt(envelope);
     } else if (envelope.isPreKeySignalMessage() || envelope.isSignalMessage()) {
-      handleMessage(envelope, source);
+      handleMessage(envelope);
     } else {
       Log.w(TAG, "Received envelope of unknown type: " + envelope.getType());
     }
   }
 
-  private void handleMessage(SignalServiceEnvelope envelope, Address source) {
-    Recipient  recipients = Recipient.from(context, source, false);
-    JobManager jobManager = ApplicationContext.getInstance(context).getJobManager();
-
-    if (!recipients.isBlocked()) {
-      long messageId = DatabaseFactory.getPushDatabase(context).insert(envelope);
-      jobManager.add(new PushDecryptJob(context, messageId));
-    } else {
-      Log.w(TAG, "*** Received blocked push message, ignoring...");
-    }
+  private void handleMessage(SignalServiceEnvelope envelope) {
+    long messageId = DatabaseFactory.getPushDatabase(context).insert(envelope);
+    ApplicationContext.getInstance(context)
+                      .getJobManager()
+                      .add(new PushDecryptJob(context, messageId));
   }
 
   private void handleReceipt(SignalServiceEnvelope envelope) {

src/org/thoughtcrime/securesms/util/GroupUtil.java

@@ -3,14 +3,23 @@ package org.thoughtcrime.securesms.util;
 import android.content.Context;
 import android.support.annotation.NonNull;
 import android.support.annotation.Nullable;
+import android.support.annotation.WorkerThread;
+
+import com.google.protobuf.ByteString;
 
 import org.thoughtcrime.securesms.R;
 import org.thoughtcrime.securesms.database.Address;
+import org.thoughtcrime.securesms.database.DatabaseFactory;
+import org.thoughtcrime.securesms.database.GroupDatabase;
 import org.thoughtcrime.securesms.logging.Log;
+import org.thoughtcrime.securesms.mms.OutgoingGroupMediaMessage;
 import org.thoughtcrime.securesms.recipients.Recipient;
 import org.thoughtcrime.securesms.recipients.RecipientModifiedListener;
+import org.thoughtcrime.securesms.sms.MessageSender;
+import org.whispersystems.libsignal.util.guava.Optional;
 
 import java.io.IOException;
+import java.util.Collections;
 import java.util.LinkedList;
 import java.util.List;
 
@@ -20,7 +29,7 @@ public class GroupUtil {
 
   private static final String ENCODED_SIGNAL_GROUP_PREFIX = "__textsecure_group__!";
   private static final String ENCODED_MMS_GROUP_PREFIX    = "__signal_mms_group__!";
-  private static final String TAG                  = GroupUtil.class.getSimpleName();
+  private static final String TAG                         = GroupUtil.class.getSimpleName();
 
   public static String getEncodedId(byte[] groupId, boolean mms) {
     return (mms ? ENCODED_MMS_GROUP_PREFIX  : ENCODED_SIGNAL_GROUP_PREFIX) + Hex.toStringCondensed(groupId);
@@ -42,6 +51,33 @@ public class GroupUtil {
     return groupId.startsWith(ENCODED_MMS_GROUP_PREFIX);
   }
 
+  @WorkerThread
+  public static Optional<OutgoingGroupMediaMessage> createGroupLeaveMessage(@NonNull Context context, @NonNull Recipient groupRecipient) {
+    String        encodedGroupId = groupRecipient.getAddress().toGroupString();
+    GroupDatabase groupDatabase  = DatabaseFactory.getGroupDatabase(context);
+
+    if (!groupDatabase.isActive(encodedGroupId)) {
+      Log.w(TAG, "Group has already been left.");
+      return Optional.absent();
+    }
+
+    ByteString decodedGroupId;
+    try {
+      decodedGroupId = ByteString.copyFrom(getDecodedId(encodedGroupId));
+    } catch (IOException e) {
+      Log.w(TAG, "Failed to decode group ID.", e);
+      return Optional.absent();
+    }
+
+    GroupContext groupContext = GroupContext.newBuilder()
+                                            .setId(decodedGroupId)
+                                            .setType(GroupContext.Type.QUIT)
+                                            .build();
+
+    return Optional.of(new OutgoingGroupMediaMessage(groupRecipient, groupContext, null, System.currentTimeMillis(), 0, null, Collections.emptyList()));
+  }
+
+
   public static @NonNull GroupDescription getDescription(@NonNull Context context, @Nullable String encodedGroup) {
     if (encodedGroup == null) {
       return new GroupDescription(context, null);