show commands command WIP

lib/slack-ruby-bot/commands.rb

@@ -2,4 +2,5 @@
 require 'slack-ruby-bot/commands/about'
 require 'slack-ruby-bot/commands/help'
 require 'slack-ruby-bot/commands/hi'
+require 'slack-ruby-bot/commands/commands'
 require 'slack-ruby-bot/commands/unknown'

lib/slack-ruby-bot/commands/commands.rb

@@ -0,0 +1,27 @@
+module SlackRubyBot
+  module Commands
+    class Commands < Base
+      BUILTIN_COMMAND_CLASSES = [SlackRubyBot::Commands::Help, SlackRubyBot::Commands::Hi].freeze
+
+      class << self
+        def call(client, data, _match)
+          commands = (BUILTIN_COMMAND_CLASSES + external_command_classes).map { |c| c.routes.keys }.flatten
+          client.say(channel: data.channel, text: "*Possible commands:*\n#{commands.join("\n")}")
+        end
+
+        private
+
+        def command_classes
+          SlackRubyBot::Commands::Base.descendants
+        end
+
+        def external_command_classes
+          command_classes.reject do |k|
+            k.name && k.name.start_with?('SlackRubyBot::Commands') || k == SlackRubyBot::Bot
+          end
+        end
+      end
+
+    end
+  end
+end