message computation

messages.java

// All lists are immutable
public ComputedMessage computeAll(@Nullable Message parent) {
  Message self = null;

  if (parent == null) {
    self = this;
  } else {
    self = Messages.compute(parent, self);
  }

  List<ComputedMessage> newChildren = new ArrayList<Message>();

  for(Message message: getChildren()) {
    newChildren.add(message.computeAll(self));
  }

  return new ComputedMessage(self, newChildren);
}

// compute Message{color = blue, children = [Message{}]} = ComputedMessage{color = blue, children = [ComputedMessage{color_computed=blue}]

// Done so we can cache the original Message
class ComputedMessage implements Message {
  
  private Message handle;
  private List<Message> children;
  
  public ComputedMessage(Message handle, List<Message> children) {
    this.handle = handle;
  }
  
  // also likely will have constructor if there is a parent message
  
  // this and other proxies
  public TextColor getColor() {
    return this.handle.getColor();
  }
  
}