Rework XMPP Error class design

Introduce AbstractError, change 'Conditions' to enums. Because of
AbstractError, it was necessary that PlainStreamElement and
TopLevelStreamElement becomes an interface. Thus the implementation of
TopLevelStreamElement.toString() had to be removed.

This adds

- policy-violation
- unexpected-request

to XMPPError.Condition, and removes the

- payment-required
- remote-server-error
- unexpected-condition
- request-timeout

Conditions

The file transfer code does now no longer throw XMPPErrorExceptions, but
SmackExceptions.

Fixes SMACK-608. Makes it possible to resolves SMACK-386.

smack-tcp/src/main/java/org/jivesoftware/smack/tcp/XMPPTCPConnection.java

@@ -1101,7 +1101,7 @@ public class XMPPTCPConnection extends AbstractXMPPConnection {
                             break;
                         case Failed.ELEMENT:
                             Failed failed = ParseStreamManagement.failed(parser);
-                            XMPPError xmppError = failed.getXMPPError();
+                            XMPPError xmppError = new XMPPError(failed.getXMPPErrorCondition());
                             XMPPException xmppException = new XMPPErrorException("Stream Management failed", xmppError);
                             // If only XEP-198 would specify different failure elements for the SM
                             // enable and SM resume failure case. But this is not the case, so we

smack-tcp/src/main/java/org/jivesoftware/smack/tcp/sm/packet/StreamManagement.java

@@ -189,25 +189,26 @@ public class StreamManagement {
     public static class Failed extends FullStreamElement {
         public static final String ELEMENT = "failed";
 
-        private XMPPError error;
+        private XMPPError.Condition condition;
 
         public Failed() {
         }
 
-        public Failed(XMPPError error) {
-            this.error = error;
+        public Failed(XMPPError.Condition condition) {
+            this.condition = condition;
         }
 
-        public XMPPError getXMPPError() {
-            return error;
+        public XMPPError.Condition getXMPPErrorCondition() {
+            return condition;
         }
 
         @Override
         public CharSequence toXML() {
             XmlStringBuilder xml = new XmlStringBuilder(this);
-            if (error != null) {
+            if (condition != null) {
                 xml.rightAngleBracket();
-                xml.append(error.toXML());
+                xml.append(condition.toString());
+                xml.xmlnsAttribute(XMPPError.NAMESPACE);
                 xml.closeElement(ELEMENT);
             }
             else {

smack-tcp/src/main/java/org/jivesoftware/smack/tcp/sm/provider/ParseStreamManagement.java

@@ -44,7 +44,7 @@ public class ParseStreamManagement {
     public static Failed failed(XmlPullParser parser) throws XmlPullParserException, IOException {
         ParserUtils.assertAtStartTag(parser);
         String name;
-        String condition = "unknown";
+        XMPPError.Condition condition = null;
         outerloop:
         while(true) {
             int event = parser.next();
@@ -53,7 +53,7 @@ public class ParseStreamManagement {
                 name = parser.getName();
                 String namespace = parser.getNamespace();
                 if (XMPPError.NAMESPACE.equals(namespace)) {
-                    condition = name;
+                    condition = XMPPError.Condition.fromString(name);
                 }
                 break;
             case XmlPullParser.END_TAG:
@@ -65,8 +65,7 @@ public class ParseStreamManagement {
             }
         }
         ParserUtils.assertAtEndTag(parser);
-        XMPPError error = new XMPPError(condition);
-        return new Failed(error);
+        return new Failed(condition);
     }
 
     public static Resumed resumed(XmlPullParser parser) throws XmlPullParserException, IOException {

smack-tcp/src/test/java/org/jivesoftware/smack/tcp/sm/provider/ParseStreamManagementTest.java

@@ -19,6 +19,7 @@
 package org.jivesoftware.smack.tcp.sm.provider;
 
 import com.jamesmurty.utils.XMLBuilder;
+
 import org.jivesoftware.smack.packet.XMPPError;
 import org.jivesoftware.smack.tcp.sm.packet.StreamManagement;
 import org.jivesoftware.smack.util.PacketParserUtils;
@@ -34,6 +35,7 @@ import static org.hamcrest.CoreMatchers.is;
 import static org.hamcrest.CoreMatchers.notNullValue;
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertThat;
+import static org.junit.Assert.assertTrue;
 
 public class ParseStreamManagementTest {
     private static final Properties outputProperties = initOutputProperties();
@@ -83,19 +85,16 @@ public class ParseStreamManagementTest {
                 PacketParserUtils.getParserFor(failedStanza));
 
         assertThat(failedPacket, is(notNullValue()));
-        XMPPError error = failedPacket.getXMPPError();
-
-        assertThat(error, is(notNullValue()));
-        assertThat(error.getCondition(), equalTo("unknown"));
+        assertTrue(failedPacket.getXMPPErrorCondition() == null);
     }
 
     @Test
     public void testParseFailedError() throws Exception {
-        String errorCondition = "failure";
+        XMPPError.Condition errorCondition = XMPPError.Condition.unexpected_request;
 
         String failedStanza = XMLBuilder.create("failed")
                 .a("xmlns", "urn:xmpp:sm:3")
-                .element(errorCondition, XMPPError.NAMESPACE)
+                .element(errorCondition.toString(), XMPPError.NAMESPACE)
                 .asString(outputProperties);
 
         System.err.println(failedStanza);
@@ -104,10 +103,7 @@ public class ParseStreamManagementTest {
                 PacketParserUtils.getParserFor(failedStanza));
 
         assertThat(failedPacket, is(notNullValue()));
-        XMPPError error = failedPacket.getXMPPError();
-
-        assertThat(error, is(notNullValue()));
-        assertThat(error.getCondition(), equalTo(errorCondition));
+        assertTrue(failedPacket.getXMPPErrorCondition() == errorCondition);
     }
 
     @Test