Rave: A Google Wave robot client framework for Ruby¶ ↑

Rave is a framework for building robot applications to participate in Google Wave conversations. See wave.google.com/ for Google Wave details. Or if you are interested in the ins-and-outs of the Google Wave protocol, check out www.waveprotocol.org/

Thanks to Spooner (Bil Bas) and Wijnand (Wijnand Wiersma) for their contributions!

Want to contribute? Just fork this project, make a branch, do some stuff and send me a merge request. There are several issues under the issue tracker at github.com/diminish7/rave/issues. If someone is actively working on an issue, it will be tagged with the developer’s name (one of the blue labels), but other than those, they’re all up for grabs. Just try to let me know what you’re planning on so we don’t overlap work.

Both Rave and Google Wave are super-alpha. There are a lot of things in the protocol that aren’t implemented in Rave yet. And the protocol is changing, so the things that are implemented are likely to break at some point. I will try to keep up, but if you notice anything broken, or if you have a need for something that isn’t implemented yet, shoot me an email: diminish7 at gmail dot com.

Okay. You’ve been warned.

Since Google currently requires that all robots run on App Engine, this tutorial assumes you are using JRuby. You should have JRuby already installed, and you should have the App Engine SDK installed. You can find more information on JRuby at jruby.org/, and you can find more information about the App Engine SDK at code.google.com/appengine/downloads.html

sudo jruby -S gem install rave

Rave comes with a “rave” executable that, among other things, sets up the project structure for you. Setting up a new project looks like this:

jruby -S rave create [robot_name] [options]

The options include profile_url and image_url, which will set the URL for the robot’s profile and avatar, respectively. Here’s how the example project “appropriate casey” was set up:

jruby -S rave create appropriate-casey profile_url=http://appropriate-casey.appspot.com/ image_url=http://appropriate-casey.appspot.com/image.png

This will stub out a project called “appropriate-casey”. It automatically creates a robot class AppropriateCasey, creates the config files for both Rack and Warbler, and creates the appengine-web.xml file that App Engine will need. For the App Engine file, it assumes that the App Engine project name is the same as the robot’s name. So in this case, the application name is appropriate-casey, which means I have to have the URL appropriate-casey.appspot.com. If you name your robot something different than the App Engine application ID, just change the <application> line in appengine-web.xml.

The robot.rb file that Rave created contains a class that extends Rave::Models::Robot. All of the logic needed for your robot to talk to App Engine is included in Rave::Models::Robot, so all you really need to do now is define your robot’s event listeners. Here is a list of the events that Google Wave can send your robot:

• WAVELET_BLIP_CREATED

• WAVELET_BLIP_REMOVED

• WAVELET_PARTICIPANTS_CHANGED

• WAVELET_TIMESTAMP_CHANGED

• WAVELET_TITLE_CHANGED

• WAVELET_VERSION_CHANGED

• BLIP_CONTRIBUTORS_CHANGED

• BLIP_DELETED

• BLIP_SUBMITTED

• BLIP_TIMESTAMP_CHANGED

• BLIP_VERSION_CHANGED

• DOCUMENT_CHANGED

• FORM_BUTTON_CLICKED

• WAVELET_CREATED

• OPERATION_ERROR

Note: Not all of these events are actually sent by Wave, even if you ask for them.

To add a listener to your robot that will respond to a given event, just define a method with the lower-case version of the event name, that accepts an event and a context. So, I want appropriate-casey to do something whenever a blip is submitted (the BLIP_SUBMITTED event), so I add the following method to my robot:

def blip_submitted(event, context)
   # Do some stuff
end

The Event object contains the following properties:

• type (The type of Event, “BLIP_SUBMITTED” in this case)

• timestamp (the timestamp that the event occurred)

• modified_by (the User who modified the document)

• blip (The Blip that the Event is associated with, otherwise the root Blip of the Wavelet that the Event is associated with)

• …other attributes, varying by Event type (see the rdoc documentation for details).

The Context object contains the following properties:

• waves (A hash - the keys are the wave IDs, and the values are the Waves)

• wavelets (A hash - the keys are the wavelet IDs, and the values are the Wavelets)

• blips (A hash - the keys are the blip IDs, and the values are the Blips)

• users (A hash - the keys are the IDs, such as bot@appspot.com, and the values are the Users)

See the Google Wave documentation for definitions of each of these things…

So, with Appropriate Casey, I want to create a robot that looks for people “shouting” in Waves (i.e. writing in all caps with a lot of exclamation points) and convert the text into a more appropriate case. So “I’M NOT YELLING!!!!” would get converted to “I’m not yelling.” To do this, I just create a blip_submitted method in my robot that looks like this:

def blip_submitted(event, context)
  blip = event.blip # Blip that was submitted.
  text = blip.content
  text.gsub!(/(\s*)([^!\.\?]+)/) { $1 + $2.capitalize } # Capitalize sentances.
  text.gsub!(/\.*!+/, '.') # Calm down exclaimations.
  text.gsub!(/\?+/, '?') # Calm down question marks.
  blip.set_text(text) if text != blip.content
end

Here’s what’s going on: First, I grab the blip that’s been modified (event.blip) and check it’s content. Any character that is capital that isn’t the start of a sentence gets downcased, any character that is lower case and DOES start a sentence gets upper cased. Exclamations get turned into a period (and additional exclamation points get dropped). There is one API method being called: Blip#set_text. This methods updates the content of the blip locally (so the changes happen optimistically) and then sends an operation request back to the server so that all users can see the changes.

So that’s it. Pretty simple, really. You can take a look under the examples/ folder for all the code.

I’m assuming that you have an application set up on App Engine already. Again, for the time being, all robots have to be on App Engine to work with Google Wave.

First of all, we need to turn our project into the correct format for App Engine. There is a utility in the “rave” executable for this, so from your robot’s top-level folder, run:

jruby -S rave war

This is basically just a wrapper around the warbler gem, but with some additional cleanup to get things in the right format for App Engine. For example, the complete JRuby jar is too large for App Engine, so Rave replaces it with two jars. Once you’ve run “rave war”, you’ll see a tmp/ folder, and a .war file. You can ignore the .war file, as App Engine needs the unpacked version. The tmp/war folder is what will get deployed.

The worst part about App Engine is testing…

Rave includes a “server” command that starts up Rack for your application, but that is of limited use, since App Engine has many App Engine-specific issues. Better to use the App Engine SDK (which is still not a perfect match to the deployed environment, but it’s better). The App Engine SDK comes with a dev_server command.

From your project directory run:

path/to/appengine_sdk/bin/dev_server tmp/war

This will start the development server on port 8080. You can now hit the following three URLs:

• localhost:8080/_wave/capabilities.xml

• localhost:8080/_wave/robot/profile

• localhost:8080/_wave/robot/jsonrpc

The first two are GETs, but the last one requires a POST. See the Google Wave protocol for the expected body of the POST if you want to test locally.

Rave includes a command for deploying to appengine. You can run:

jruby -S rave appengine_deploy

For this to work, you’ll need to have downloaded the Google Appengine Java SDK, and have it

1) on your path
2) defined in an environment variable called APPENGINE_JAVA_SDK, or
3) defined in config.yaml as appcfg['sdk]

Note that running appengine_deploy will also run the “war” command if needed, so there is no need run “war” first.

Note: Whenever you deploy a new version of your robot and try to use it, it will appear to not do anything because it takes a long time to start up the system on appengine. You probably won’t get anything happening for about 30 seconds after the bot first receives a Wave event, but after that it should work fine.

From a Google Wave client, start a new wave, and invite your robot as a participant. Your robot’s user name will be [robot_name]@appspot.com. So Casey is at appropriate-casey@appspot.com.

That’s it. Enjoy!