Attach group visibility to MessageSharedEvent.

This allows listeners to decide whether to act on the event.

bramble-core/src/main/java/org/briarproject/bramble/db/Database.java

@@ -320,6 +320,13 @@ interface Database<T> {
 	 */
 	Group getGroup(T txn, GroupId g) throws DbException;
 
+	/**
+	 * Returns the ID of the group containing the given message.
+	 * <p/>
+	 * Read-only.
+	 */
+	GroupId getGroupId(T txn, MessageId m) throws DbException;
+
 	/**
 	 * Returns the metadata for the given group.
 	 * <p/>

bramble-core/src/main/java/org/briarproject/bramble/db/DatabaseComponentImpl.java

@@ -287,7 +287,12 @@ class DatabaseComponentImpl<T> implements DatabaseComponent {
 			transaction.attach(new MessageAddedEvent(m, null));
 			transaction.attach(new MessageStateChangedEvent(m.getId(), true,
 					DELIVERED));
-			if (shared) transaction.attach(new MessageSharedEvent(m.getId()));
+			if (shared) {
+				Map<ContactId, Boolean> visibility =
+						db.getGroupVisibility(txn, m.getGroupId());
+				transaction.attach(new MessageSharedEvent(m.getId(),
+						m.getGroupId(), visibility));
+			}
 		}
 		db.mergeMessageMetadata(txn, m.getId(), meta);
 	}
@@ -550,6 +555,15 @@ class DatabaseComponentImpl<T> implements DatabaseComponent {
 		return db.getGroup(txn, g);
 	}
 
+	@Override
+	public GroupId getGroupId(Transaction transaction, MessageId m)
+			throws DbException {
+		T txn = unbox(transaction);
+		if (!db.containsMessage(txn, m))
+			throw new NoSuchMessageException();
+		return db.getGroupId(txn, m);
+	}
+
 	@Override
 	public Metadata getGroupMetadata(Transaction transaction, GroupId g)
 			throws DbException {
@@ -1184,7 +1198,9 @@ class DatabaseComponentImpl<T> implements DatabaseComponent {
 		if (db.getMessageState(txn, m) != DELIVERED)
 			throw new IllegalArgumentException("Shared undelivered message");
 		db.setMessageShared(txn, m, true);
-		transaction.attach(new MessageSharedEvent(m));
+		GroupId g = db.getGroupId(txn, m);
+		Map<ContactId, Boolean> visibility = db.getGroupVisibility(txn, g);
+		transaction.attach(new MessageSharedEvent(m, g, visibility));
 	}
 
 	@Override

bramble-core/src/main/java/org/briarproject/bramble/db/JdbcDatabase.java

@@ -1683,6 +1683,27 @@ abstract class JdbcDatabase implements Database<Connection> {
 		}
 	}
 
+	@Override
+	public GroupId getGroupId(Connection txn, MessageId m) throws DbException {
+		PreparedStatement ps = null;
+		ResultSet rs = null;
+		try {
+			String sql = "SELECT groupId FROM messages WHERE messageId = ?";
+			ps = txn.prepareStatement(sql);
+			ps.setBytes(1, m.getBytes());
+			rs = ps.executeQuery();
+			if (!rs.next()) throw new DbStateException();
+			GroupId g = new GroupId(rs.getBytes(1));
+			rs.close();
+			ps.close();
+			return g;
+		} catch (SQLException e) {
+			tryToClose(rs, LOG, WARNING);
+			tryToClose(ps, LOG, WARNING);
+			throw new DbException(e);
+		}
+	}
+
 	@Override
 	public Collection<Group> getGroups(Connection txn, ClientId c,
 			int majorVersion) throws DbException {

bramble-core/src/main/java/org/briarproject/bramble/sync/DuplexOutgoingSession.java

@@ -44,6 +44,7 @@ import java.util.logging.Logger;
 import javax.annotation.Nullable;
 import javax.annotation.concurrent.ThreadSafe;
 
+import static java.lang.Boolean.TRUE;
 import static java.util.concurrent.TimeUnit.MILLISECONDS;
 import static java.util.logging.Level.INFO;
 import static java.util.logging.Level.WARNING;
@@ -233,7 +234,10 @@ class DuplexOutgoingSession implements SyncSession, EventListener {
 			ContactRemovedEvent c = (ContactRemovedEvent) e;
 			if (c.getContactId().equals(contactId)) interrupt();
 		} else if (e instanceof MessageSharedEvent) {
-			generateOffer();
+			MessageSharedEvent m = (MessageSharedEvent) e;
+			if (m.getGroupVisibility().get(contactId) == TRUE) {
+				generateOffer();
+			}
 		} else if (e instanceof GroupVisibilityUpdatedEvent) {
 			GroupVisibilityUpdatedEvent g = (GroupVisibilityUpdatedEvent) e;
 			if (g.getVisibility() == SHARED &&