Add support for passing a Proc to routes

Add support for passing a Proc to routes instead of a regular
expression for matching - this proc will then be called with the message
in the context of the handler object and should return a boolean
indicating whether the route matches or not.

This allows for dynamically defined routing, plus support for
configuring things like command names and prefixes, which is useful as
plugin configuration is only available on a handler instance, not the
singleton.

Probably addresses most of what #100 is asking for

lib/lita/handler/chat_router.rb

@@ -31,7 +31,9 @@ class Route
 
       # @overload route(pattern, method_name, **options)
       #   Creates a chat route.
-      #   @param pattern [Regexp] A regular expression to match incoming messages against.
+      #   @param pattern [Regexp, Proc] Either a regular expression to match incoming messages against, or a
+      #     Proc that will be called in the context of the handler with the message, and should return a
+      #     boolean indicating whether that message matches the route
       #   @param method_name [Symbol, String] The name of the instance method to trigger.
       #   @param command [Boolean] Whether or not the message must be directed at the robot.
       #   @param restrict_to [Array<Symbol, String>, nil] An optional list of authorization
@@ -41,7 +43,9 @@ class Route
       #   @return [void]
       # @overload route(pattern, **options)
       #   Creates a chat route.
-      #   @param pattern [Regexp] A regular expression to match incoming messages against.
+      #   @param pattern [Regexp, Proc] Either a regular expression to match incoming messages against, or a
+      #     Proc that will be called in the context of the handler with the message, and should return a
+      #     boolean indicating whether that message matches the route
       #   @param command [Boolean] Whether or not the message must be directed at the robot.
       #   @param restrict_to [Array<Symbol, String>, nil] An optional list of authorization
       #     groups the user must be in to trigger the route.

lib/lita/route_validator.rb

@@ -59,7 +59,11 @@ def from_self?(message, robot)
 
     # Message must match the pattern
     def matches_pattern?(route, message)
-      route.pattern === message.body
+      if route.pattern.is_a?(Regexp)
+        route.pattern === message.body
+      else
+        handler.instance_exec(message, &route.pattern)
+      end
     end
 
     # Allow custom route hooks to reject the route

spec/lita/handler/chat_router_spec.rb

@@ -11,6 +11,7 @@ def self.name
   route(/command/, :command, command: true)
   route(/admin/, :admin, restrict_to: :admins)
   route(/error/, :error)
+  route(:proc_route?, :trigger_proc_route)
   route(/validate route hook/, :validate_route_hook, code_word: true)
   route(/trigger route hook/, :trigger_route_hook, custom_data: "trigger route hook")
 
@@ -30,6 +31,14 @@ def error(_response)
     raise
   end
 
+  def proc_route?(message)
+    message == "proc route"
+  end
+
+  def trigger_proc_route
+    response.reply("trigger proc route")
+  end
+
   def validate_route_hook(response)
     response.reply("validate route hook")
   end
@@ -50,6 +59,11 @@ def trigger_route_hook(response)
       expect(replies.last).to eq("message")
     end
 
+    it "routes messages satisfying a proc to the supplied method" do
+      send_message("proc route")
+      expect(replies.last).to eq("proc route")
+    end
+
     it "routes a matching message even if addressed to the robot" do
       send_command("message")
       expect(replies.last).to eq("message")