moves delay element references to xmpp package

src/main/java/de/thedevstack/conversationsplus/generator/MessageGenerator.java

@@ -17,6 +17,7 @@ import de.thedevstack.conversationsplus.entities.Message;
 import de.thedevstack.conversationsplus.xml.Element;
 import de.thedevstack.conversationsplus.xmpp.carbons.Carbons;
 import de.thedevstack.conversationsplus.xmpp.chatstate.ChatState;
+import de.thedevstack.conversationsplus.xmpp.delay.Delay;
 import de.thedevstack.conversationsplus.xmpp.httpuploadim.HttpUploadHint;
 import de.thedevstack.conversationsplus.xmpp.jid.Jid;
 import de.thedevstack.conversationsplus.xmpp.openpgp.OpenPgpXep;
@@ -28,7 +29,7 @@ public class MessageGenerator extends AbstractGenerator {
 	/**
 	 * Moved to messaging.MessageGenerator
 	 */
-	private MessagePacket preparePacket(Message message) {
+	protected MessagePacket preparePacket(Message message) {
 		Conversation conversation = message.getConversation();
 		Account account = conversation.getAccount();
 		MessagePacket packet = new MessagePacket();
@@ -59,7 +60,7 @@ public class MessageGenerator extends AbstractGenerator {
 		final SimpleDateFormat mDateFormat = new SimpleDateFormat(
 				"yyyy-MM-dd'T'HH:mm:ss.SSS'Z'", Locale.US);
 		mDateFormat.setTimeZone(TimeZone.getTimeZone("UTC"));
-		Element delay = packet.addChild("delay", "urn:xmpp:delay");
+		Element delay = packet.addChild(Delay.DELAY.getXmlElement());
 		Date date = new Date(timestamp);
 		delay.setAttribute("stamp", mDateFormat.format(date));
 	}

src/main/java/de/thedevstack/conversationsplus/parser/AbstractParser.java

@@ -9,6 +9,7 @@ import de.thedevstack.conversationsplus.entities.Account;
 import de.thedevstack.conversationsplus.entities.Contact;
 import de.thedevstack.conversationsplus.services.XmppConnectionService;
 import de.thedevstack.conversationsplus.xml.Element;
+import de.thedevstack.conversationsplus.xmpp.delay.Delay;
 import de.thedevstack.conversationsplus.xmpp.jid.Jid;
 import de.thedevstack.conversationsplus.xmpp.stanzas.AbstractStanza;
 
@@ -30,7 +31,7 @@ public abstract class AbstractParser {
      *  attribute the current time is returned.
      */
 	public static Long getTimestamp(Element element, Long defaultValue) {
-		Element delay = element.findChild("delay","urn:xmpp:delay");
+		Element delay = element.findChild(Delay.DELAY);
 		if (delay != null) {
 			String stamp = delay.getAttribute("stamp");
 			if (stamp != null) {

src/main/java/de/thedevstack/conversationsplus/xml/Element.java

@@ -31,18 +31,18 @@ public class Element {
 	}
 
 	public Element addChild(String name) {
-		this.content = null;
-		Element child = new Element(name);
-		children.add(child);
-		return child;
+		return this.addChild(new Element(name));
 	}
 
 	public Element addChild(String name, String xmlns) {
-		this.content = null;
 		Element child = new Element(name);
 		child.setAttribute("xmlns", xmlns);
 		children.add(child);
-		return child;
+		return this.addChild(child);
+	}
+
+	public Element addChild(XmlElementContainer container) {
+		return this.addChild(container.getXmlElement());
 	}
 
 	public Element setContent(String content) {

src/main/java/de/thedevstack/conversationsplus/xmpp/delay/Delay.java

@@ -0,0 +1,27 @@
+package de.thedevstack.conversationsplus.xmpp.delay;
+
+import de.thedevstack.conversationsplus.xml.Element;
+import de.thedevstack.conversationsplus.xml.XmlElementContainer;
+
+/**
+ */
+public enum Delay implements XmlElementContainer {
+    DELAY("delay");
+
+    private Element xmlElement;
+
+    Delay(String elementName) {
+        this.xmlElement = new Element(elementName, NAMESPACE);
+    }
+
+    @Override
+    public Element getXmlElement() {
+        return xmlElement;
+    }
+
+    /**
+     * The namespace of the delay timestamp as defined in XEP-0203.
+     * @see <a href="https://xmpp.org/extensions/xep-0203.html">https://xmpp.org/extensions/xep-0203.html</a>
+     */
+    public static final String NAMESPACE = "urn:xmpp:delay";
+}