first pass at DSL and at_exit running interface

* Need to make a better decision about exactly when we want to start the server, but maybe a convention for file names isn't terrible for now
* The signature of the 'on' method feels sloppy, and well the DSL itself I feel could be a lot better...probably need to think
  outside the Probot library's use of on to see if there's some interesting grammar of sorts that Ruby could do well in a way that
  JavaScript can't always do based on its syntactical limitations

examples/demo/.env

@@ -0,0 +1,28 @@
+PRUBOT_ID=1
+PRUBOT_KEY="-----BEGIN RSA PRIVATE KEY-----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+-----END RSA PRIVATE KEY-----"

examples/demo/app.rb

@@ -0,0 +1,9 @@
+require 'prubot'
+
+on 'test-event', 'say howdy' do
+  'howdy'
+end
+
+on 'test-action', 'test-event', 'say hello' do
+  'hello'
+end

examples/register/app.rb

@@ -0,0 +1,9 @@
+require 'prubot'
+
+on 'test-event', 'say howdy' do
+  'howdy'
+end
+
+on 'test-action', 'test-event', 'say hello' do
+  'hello'
+end

examples/welcomemat.rb

@@ -2,7 +2,7 @@
 
 require 'prubot'
 
-on 'issues', 'opened', 'add a welcome message' do
+on 'opened', 'issues', 'add a welcome message' do
   # `payload` is a hash of the event payload.
   discussions_link = payload['repository']['discussions_url']
   welcome_message = 'Thanks for stopping by :wave:. While we work on getting back to you '\

lib/prubot.rb

@@ -32,6 +32,14 @@ def configured?
       @config.configured?
     end
 
+    def run!
+      Rack::Handler::WEBrick.run(app)
+    end
+
+    def run?
+      $0 == 'app.rb' # HACK HACK HACK need to decide how we want to handle this.
+    end
+
     def register_event(name, event, action = nil, &block)
       raise Error 'block required' unless block
 
@@ -47,4 +55,27 @@ def setup_routing
       end
     end
   end
+
+  module DSL
+    @@app = Prubot::Application.new
+
+    ##
+    # Supports both +on 'event' 'description' do...+ and +on 'action', 'event', 'description' do...+
+    # based on the number of arguments passed. We are careful to flip the arguments around based
+    # on the signature of the event registration method.
+    def on(*args, &block)
+      case args.length
+      when 2
+        @@app.register_event(args[1], args[0], &block)
+      when 3
+        @@app.register_event(args[2], args[1], args[0], &block)
+      else
+        raise Prubot::Error 'on supports either "on <event> <description> do..." or "on <action> <event> <description> do..."'
+      end
+    end
+
+    at_exit { @@app.run! if @@app.run? }
+  end
 end
+
+extend Prubot::DSL