xmpp: Communicate stream closure from the buffer

lib/xmpp/buffer.dart

@@ -20,9 +20,11 @@ class XmlStreamBuffer extends StreamTransformerBase<String, XMLNode> {
       toParse = toParse + "</stream:stream>";
     } else {
       if (toParse.endsWith("</stream:stream>")) {
-        // TODO: Maybe prepend <stream:stream> so that we can detect it within
-        //       [XmppConnection]
         toParse = toParse.substring(0, toParse.length - 16);
+        // In order for this class to have as little logic as possible, replace the
+        // </stream:stream> with a <stream:stream /> such that we can parse it without
+        // issue and catch it in [XmppConnection].
+        toParse += "<stream:stream />";
       }
     } 
 

lib/xmpp/connection.dart

@@ -93,7 +93,6 @@ class XmppConnection {
 
     _socketStream = _socket.getDataStream();
     // TODO: Handle on done
-    // TODO: Handle the stream buffer in the socket
     _socketStream.transform(_streamBuffer).forEach(handleXmlStream);
     _socket.getErrorStream().listen(_handleError);
 
@@ -351,6 +350,11 @@ class XmppConnection {
   void handleXmlStream(XMLNode node) async {
     _log("(xml) <== " + node.toXml());
 
+    if (node.tag == "stream:stream" && node.children.isEmpty) {
+      _handleError(null);
+      return;
+    }
+    
     switch (_routingState) {
       case RoutingState.unauthenticated: {
         // We expect the stream header here