Simplify internal post receive messages

Instead of sending varied data to Gitaly, and making Gitaly construct
various messages, build the messages first and have Gitaly print
either basic messages or alert messages, in the order they come.

Depends on https://gitlab.com/gitlab-org/gitaly/merge_requests/1410

4 files changed, 77 insertions, 17 deletions

diff --git a/lib/api/entities.rb b/lib/api/entities.rb
index 6f86adf6a5c..88be76d3c78 100644
--- a/lib/api/entities.rb
+++ b/lib/api/entities.rb
@@ -1705,6 +1705,18 @@ module API
     class ClusterGroup < Cluster
       expose :group, using: Entities::BasicGroupDetails
     end
+
+    module InternalPostReceive
+      class Message < Grape::Entity
+        expose :message
+        expose :type
+      end
+
+      class Response < Grape::Entity
+        expose :messages, using: Message
+        expose :reference_counter_decreased
+      end
+    end
   end
 end
 
diff --git a/lib/api/helpers/internal_helpers.rb b/lib/api/helpers/internal_helpers.rb
index 9afe6c5b027..6b438235258 100644
--- a/lib/api/helpers/internal_helpers.rb
+++ b/lib/api/helpers/internal_helpers.rb
@@ -44,8 +44,6 @@ module API
       end
 
       def process_mr_push_options(push_options, project, user, changes)
-        output = {}
-
         Gitlab::QueryLimiting.whitelist('https://gitlab.com/gitlab-org/gitlab-ce/issues/61359')
 
         service = ::MergeRequests::PushOptionsHandlerService.new(
@@ -56,15 +54,13 @@ module API
         ).execute
 
         if service.errors.present?
-          output[:warnings] = push_options_warning(service.errors.join("\n\n"))
+          push_options_warning(service.errors.join("\n\n"))
         end
-
-        output
       end
 
       def push_options_warning(warning)
         options = Array.wrap(params[:push_options]).map { |p| "'#{p}'" }.join(' ')
-        "Error encountered with push options #{options}: #{warning}"
+        "WARNINGS:\nError encountered with push options #{options}: #{warning}"
       end
 
       def redis_ping
diff --git a/lib/api/internal.rb b/lib/api/internal.rb
index 224aaaaf006..088ea5bd79a 100644
--- a/lib/api/internal.rb
+++ b/lib/api/internal.rb
@@ -256,25 +256,26 @@ module API
       post '/post_receive' do
         status 200
 
-        output = {} # Messages to gitlab-shell
+        response = Gitlab::InternalPostReceive::Response.new
         user = identify(params[:identifier])
         project = Gitlab::GlRepository.parse(params[:gl_repository]).first
         push_options = Gitlab::PushOptions.new(params[:push_options])
 
+        response.reference_counter_decreased = Gitlab::ReferenceCounter.new(params[:gl_repository]).decrease
+
         PostReceive.perform_async(params[:gl_repository], params[:identifier],
           params[:changes], push_options.as_json)
 
         mr_options = push_options.get(:merge_request)
-        output.merge!(process_mr_push_options(mr_options, project, user, params[:changes])) if mr_options.present?
+        if mr_options.present?
+          message = process_mr_push_options(mr_options, project, user, params[:changes])
+          response.add_alert_message(message)
+        end
 
         broadcast_message = BroadcastMessage.current&.last&.message
-        reference_counter_decreased = Gitlab::ReferenceCounter.new(params[:gl_repository]).decrease
+        response.add_alert_message(broadcast_message)
 
-        output.merge!(
-          broadcast_message: broadcast_message,
-          reference_counter_decreased: reference_counter_decreased,
-          merge_request_urls: merge_request_urls
-        )
+        response.add_merge_request_urls(merge_request_urls)
 
         # A user is not guaranteed to be returned; an orphaned write deploy
         # key could be used
@@ -282,11 +283,11 @@ module API
           redirect_message = Gitlab::Checks::ProjectMoved.fetch_message(user.id, project.id)
           project_created_message = Gitlab::Checks::ProjectCreated.fetch_message(user.id, project.id)
 
-          output[:redirected_message] = redirect_message if redirect_message
-          output[:project_created_message] = project_created_message if project_created_message
+          response.add_basic_message(redirect_message)
+          response.add_basic_message(project_created_message)
         end
 
-        output
+        present response, with: Entities::InternalPostReceive::Response
       end
     end
   end
diff --git a/lib/gitlab/internal_post_receive/response.rb b/lib/gitlab/internal_post_receive/response.rb
new file mode 100644
index 00000000000..7e7ec2aa45c
--- /dev/null
+++ b/lib/gitlab/internal_post_receive/response.rb
@@ -0,0 +1,51 @@
+# frozen_string_literal: true
+
+module Gitlab
+  module InternalPostReceive
+    class Response
+      attr_accessor :reference_counter_decreased
+      attr_reader :messages
+
+      Message = Struct.new(:message, :type) do
+        def self.basic(text)
+          new(text, :basic)
+        end
+
+        def self.alert(text)
+          new(text, :alert)
+        end
+      end
+
+      def initialize
+        @messages = []
+        @reference_counter_decreased = false
+      end
+
+      def add_merge_request_urls(urls_data)
+        urls_data.each do |url_data|
+          add_merge_request_url(url_data)
+        end
+      end
+
+      def add_merge_request_url(url_data)
+        message = if url_data[:new_merge_request]
+                    "To create a merge request for #{url_data[:branch_name]}, visit:"
+                  else
+                    "View merge request for #{url_data[:branch_name]}:"
+                  end
+
+        message += "\n  #{url_data[:url]}"
+
+        add_basic_message(message)
+      end
+
+      def add_basic_message(text)
+        @messages << Message.basic(text) if text.present?
+      end
+
+      def add_alert_message(text)
+        @messages.unshift(Message.alert(text)) if text.present?
+      end
+    end
+  end
+end