1 files changed, 131 insertions, 0 deletions
diff --git a/lib/mattermost/presenter.rb b/lib/mattermost/presenter.rb
new file mode 100644
index 00000000000..67eda983a74
--- /dev/null
+++ b/lib/mattermost/presenter.rb
@@ -0,0 +1,131 @@
+module Mattermost
+  class Presenter
+    class << self
+      include Gitlab::Routing.url_helpers
+
+      def authorize_chat_name(url)
+        message = if url
+                    ":wave: Hi there! Before I do anything for you, please [connect your GitLab account](#{url})."
+                  else
+                    ":sweat_smile: Couldn't identify you, nor can I autorize you!"
+                  end
+
+        ephemeral_response(message)
+      end
+
+      def help(commands, trigger)
+        if commands.none?
+          ephemeral_response("No commands configured")
+        else
+          commands.map! { |command| "#{trigger} #{command}" }
+          message = header_with_list("Available commands", commands)
+
+          ephemeral_response(message)
+        end
+      end
+
+      def present(subject)
+        return not_found unless subject
+
+        if subject.is_a?(Gitlab::ChatCommands::Result)
+          show_result(subject)
+        elsif subject.respond_to?(:count)
+          if subject.many?
+            multiple_resources(subject)
+          elsif subject.none?
+            not_found
+          else
+            single_resource(subject)
+          end
+        else
+          single_resource(subject)
+        end
+      end
+
+      def access_denied
+        ephemeral_response("Whoops! That action is not allowed. This incident will be [reported](https://xkcd.com/838/).")
+      end
+
+      private
+
+      def show_result(result)
+        case result.type
+        when :success
+          in_channel_response(result.message)
+        else
+          ephemeral_response(result.message)
+        end
+      end
+
+      def not_found
+        ephemeral_response("404 not found! GitLab couldn't find what you were looking for! :boom:")
+      end
+
+      def single_resource(resource)
+        return error(resource) if resource.errors.any? || !resource.persisted?
+
+        message = "### #{title(resource)}"
+        message << "\n\n#{resource.description}" if resource.try(:description)
+
+        in_channel_response(message)
+      end
+
+      def multiple_resources(resources)
+        resources.map! { |resource| title(resource) }
+
+        message = header_with_list("Multiple results were found:", resources)
+
+        ephemeral_response(message)
+      end
+
+      def error(resource)
+        message = header_with_list("The action was not successful, because:", resource.errors.messages)
+
+        ephemeral_response(message)
+      end
+
+      def title(resource)
+        reference = resource.try(:to_reference) || resource.try(:id)
+        title = resource.try(:title) || resource.try(:name)
+
+        "[#{reference} #{title}](#{url(resource)})"
+      end
+
+      def header_with_list(header, items)
+        message = [header]
+
+        items.each do |item|
+          message << "- #{item}"
+        end
+
+        message.join("\n")
+      end
+
+      def url(resource)
+        url_for(
+          [
+            resource.project.namespace.becomes(Namespace),
+            resource.project,
+            resource
+          ]
+        )
+      end
+
+      def ephemeral_response(message)
+        {
+          response_type: :ephemeral,
+          text: message,
+          status: 200
+        }
+      end
+
+      def in_channel_response(message)
+        {
+          response_type: :in_channel,
+          text: message,
+          status: 200
+        }
+      end
+    end
+  end
+end