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Make it fucking Delightful! - Michael Ducy

Ya, we really like this quote, so today we start implementing it.

It felt like we were able to delete 2 tons of code without losing features. We feel that the backend is really lean now. When start reading the code I think there are just two concepts you need to know. The Plugin-Classes and the VotesApp/WhatsApp-Classes. And for those you can have a look to this two chapters:


To understand the WhatsApp part you just need to know that we abstracted the communication behind the WhatsAppClient interface. We provide the two implementations YowsupRestClient and ConsoleClient to make the code run on production using WhatsApp (via Yowsup) and run on development via the ConsoleClient. As we mentioned already in a previous post, the selection is done by utilizing Springs @Profile.

Image of our Solution

To receive and forward the messages, we created the WhatsAppClientToReactorBridge. This classes uses the interfaces to Poll new messages (that part would be nicer with Websockets) and sends new messages. When a message is polled, it will be given to Reactor where it get caught up by the GroupMessageListener. And from there the magic with our PluginApi starts.


The PluginApi becomes really easy now. To register a plugin that listens for "Ping" and then answer "Pong!", you just need to put this lines:

public class PingCommandPlugin extends TextEqualsWordPlugin implements Describable {

  public PingCommandPlugin() {
    // varargs for the text comparsion
    super("ping", "ping?");

  public Optional<Answer> matches(final GroupMessage message, final Group group) {
    // this answer will be returned "into the group"
    return Optional.of(Answer.intoGroup(group, "Pong!"));

  public Description describe() {
    // that is the construction of the help
    return DescriptionBuilder.describe("Ping Command")
    .withTrigger("ping") // This is also a vararg
    .withDescription("Returns \"Pong!\"")

If you like to understand the already existing plugins and the hierachy of them, you can have look to this diagram:

Image of our Solution

Today we had also the Idea that it should be possible to register own plugins from inside the Chat. With this a message like "load" could import the plugin provide its service. But I gues we will not have time for this.

O damn, two days left before the deadline arrives.

Need to hurry up, bye bye :)