Add help command

lib/gitlab/chat_commands/command.rb

@@ -18,13 +18,14 @@ module Gitlab
             Gitlab::ChatCommands::Presenters::Access.new.access_denied
           end
         else
-          help(help_messages)
+          Gitlab::ChatCommands::Help.new(project, current_user, params).execute(available_commands)
         end
       end
 
       def match_command
         match = nil
-        service = available_commands.find do |klass|
+        service =
+          available_commands.find do |klass|
             match = klass.match(params[:text])
           end
 
@@ -33,10 +34,6 @@ module Gitlab
 
       private
 
-      def help_messages
-        available_commands.map(&:help_message)
-      end
-
       def available_commands
         COMMANDS.select do |klass|
           klass.available?(project)

lib/gitlab/chat_commands/help.rb

@@ -0,0 +1,28 @@
+module Gitlab
+  module ChatCommands
+    class Help < BaseCommand
+      # This class has to be used last, as it always matches. It has to match
+      # because other commands were not triggered and we want to show the help
+      # command
+      def self.match(_text)
+        true
+      end
+
+      def self.help_message
+        'help'
+      end
+
+      def self.allowed?(_project, _user)
+        true
+      end
+
+      def execute(commands)
+        Gitlab::ChatCommands::Presenters::Help.new(commands).present(trigger)
+      end
+
+      def trigger
+        params[:command]
+      end
+    end
+  end
+end

lib/gitlab/chat_commands/presenters/help.rb

@@ -0,0 +1,20 @@
+module Gitlab::ChatCommands::Presenters
+  class Help < Gitlab::ChatCommands::Presenters::Base
+    def present(trigger)
+      message =
+        if @resource.none?
+          "No commands available :thinking_face:"
+        else
+          header_with_list("Available commands", full_commands(trigger))
+        end
+
+      ephemeral_response(text: message)
+    end
+
+    private
+
+    def full_commands(trigger)
+      @resource.map { |command| "#{trigger} #{command.help_message}" }
+    end
+  end
+end