10 files changed, 100 insertions, 6 deletions
diff --git a/app/graphql/types/base_input_object.rb b/app/graphql/types/base_input_object.rb
index aebed035d3b..90a29b0cfb8 100644
--- a/app/graphql/types/base_input_object.rb
+++ b/app/graphql/types/base_input_object.rb
@@ -2,5 +2,6 @@
 
 module Types
   class BaseInputObject < GraphQL::Schema::InputObject
+    prepend Gitlab::Graphql::CopyFieldDescription
   end
 end
diff --git a/app/graphql/types/diff_paths_input_type.rb b/app/graphql/types/diff_paths_input_type.rb
new file mode 100644
index 00000000000..43feddd9827
--- /dev/null
+++ b/app/graphql/types/diff_paths_input_type.rb
@@ -0,0 +1,12 @@
+# frozen_string_literal: true
+
+module Types
+  # rubocop: disable Graphql/AuthorizeTypes
+  class DiffPathsInputType < BaseInputObject
+    argument :old_path, GraphQL::STRING_TYPE, required: false,
+              description: 'The path of the file on the start sha'
+    argument :new_path, GraphQL::STRING_TYPE, required: false,
+              description: 'The path of the file on the head sha'
+  end
+  # rubocop: enable Graphql/AuthorizeTypes
+end
diff --git a/app/graphql/types/diff_refs_type.rb b/app/graphql/types/diff_refs_type.rb
new file mode 100644
index 00000000000..33a5780cd68
--- /dev/null
+++ b/app/graphql/types/diff_refs_type.rb
@@ -0,0 +1,14 @@
+# frozen_string_literal: true
+
+module Types
+  # rubocop: disable Graphql/AuthorizeTypes
+  # Types that use DiffRefsType should have their own authorization
+  class DiffRefsType < BaseObject
+    graphql_name 'DiffRefs'
+
+    field :head_sha, GraphQL::STRING_TYPE, null: false, description: 'The sha of the head at the time the comment was made'
+    field :base_sha, GraphQL::STRING_TYPE, null: false, description: 'The merge base of the branch the comment was made on'
+    field :start_sha, GraphQL::STRING_TYPE, null: false, description: 'The sha of the branch being compared against'
+  end
+  # rubocop: enable Graphql/AuthorizeTypes
+end
diff --git a/app/graphql/types/merge_request_type.rb b/app/graphql/types/merge_request_type.rb
index 6734d4761c2..b8f63a750c5 100644
--- a/app/graphql/types/merge_request_type.rb
+++ b/app/graphql/types/merge_request_type.rb
@@ -23,6 +23,7 @@ module Types
     field :updated_at, Types::TimeType, null: false
     field :source_project, Types::ProjectType, null: true
     field :target_project, Types::ProjectType, null: false
+    field :diff_refs, Types::DiffRefsType, null: true
     # Alias for target_project
     field :project, Types::ProjectType, null: false
     field :project_id, GraphQL::INT_TYPE, null: false, method: :target_project_id
diff --git a/app/graphql/types/mutation_type.rb b/app/graphql/types/mutation_type.rb
index bc5fb709522..f843d6ad86f 100644
--- a/app/graphql/types/mutation_type.rb
+++ b/app/graphql/types/mutation_type.rb
@@ -10,5 +10,10 @@ module Types
     mount_mutation Mutations::AwardEmojis::Remove
     mount_mutation Mutations::AwardEmojis::Toggle
     mount_mutation Mutations::MergeRequests::SetWip, calls_gitaly: true
+    mount_mutation Mutations::Notes::Create::Note, calls_gitaly: true
+    mount_mutation Mutations::Notes::Create::DiffNote, calls_gitaly: true
+    mount_mutation Mutations::Notes::Create::ImageDiffNote, calls_gitaly: true
+    mount_mutation Mutations::Notes::Update
+    mount_mutation Mutations::Notes::Destroy
   end
 end
diff --git a/app/graphql/types/notes/diff_image_position_input_type.rb b/app/graphql/types/notes/diff_image_position_input_type.rb
new file mode 100644
index 00000000000..23b53b20815
--- /dev/null
+++ b/app/graphql/types/notes/diff_image_position_input_type.rb
@@ -0,0 +1,20 @@
+# frozen_string_literal: true
+
+module Types
+  module Notes
+    # rubocop: disable Graphql/AuthorizeTypes
+    class DiffImagePositionInputType < DiffPositionBaseInputType
+      graphql_name 'DiffImagePositionInput'
+
+      argument :x, GraphQL::INT_TYPE, required: true,
+               description: copy_field_description(Types::Notes::DiffPositionType, :x)
+      argument :y, GraphQL::INT_TYPE, required: true,
+               description: copy_field_description(Types::Notes::DiffPositionType, :y)
+      argument :width, GraphQL::INT_TYPE, required: true,
+               description: copy_field_description(Types::Notes::DiffPositionType, :width)
+      argument :height, GraphQL::INT_TYPE, required: true,
+               description: copy_field_description(Types::Notes::DiffPositionType, :height)
+    end
+    # rubocop: enable Graphql/AuthorizeTypes
+  end
+end
diff --git a/app/graphql/types/notes/diff_position_base_input_type.rb b/app/graphql/types/notes/diff_position_base_input_type.rb
new file mode 100644
index 00000000000..a9b4e1a8948
--- /dev/null
+++ b/app/graphql/types/notes/diff_position_base_input_type.rb
@@ -0,0 +1,22 @@
+# frozen_string_literal: true
+
+module Types
+  module Notes
+    # rubocop: disable Graphql/AuthorizeTypes
+    class DiffPositionBaseInputType < BaseInputObject
+      argument :head_sha, GraphQL::STRING_TYPE, required: true,
+               description: copy_field_description(Types::DiffRefsType, :head_sha)
+      argument :base_sha,  GraphQL::STRING_TYPE, required: false,
+               description: copy_field_description(Types::DiffRefsType, :base_sha)
+      argument :start_sha, GraphQL::STRING_TYPE, required: true,
+               description: copy_field_description(Types::DiffRefsType, :start_sha)
+
+      argument :paths,
+               Types::DiffPathsInputType,
+               required: true,
+               description: 'The paths of the file that was changed. ' \
+                            'Both of the properties of this input are optional, but at least one of them is required'
+    end
+    # rubocop: enable Graphql/AuthorizeTypes
+  end
+end
diff --git a/app/graphql/types/notes/diff_position_input_type.rb b/app/graphql/types/notes/diff_position_input_type.rb
new file mode 100644
index 00000000000..02c91e173cb
--- /dev/null
+++ b/app/graphql/types/notes/diff_position_input_type.rb
@@ -0,0 +1,16 @@
+# frozen_string_literal: true
+
+module Types
+  module Notes
+    # rubocop: disable Graphql/AuthorizeTypes
+    class DiffPositionInputType < DiffPositionBaseInputType
+      graphql_name 'DiffPositionInput'
+
+      argument :old_line, GraphQL::INT_TYPE, required: false,
+               description: copy_field_description(Types::Notes::DiffPositionType, :old_line)
+      argument :new_line, GraphQL::INT_TYPE, required: true,
+               description: copy_field_description(Types::Notes::DiffPositionType, :new_line)
+    end
+    # rubocop: enable Graphql/AuthorizeTypes
+  end
+end
diff --git a/app/graphql/types/notes/diff_position_type.rb b/app/graphql/types/notes/diff_position_type.rb
index ebc24451715..6a0377fbfdf 100644
--- a/app/graphql/types/notes/diff_position_type.rb
+++ b/app/graphql/types/notes/diff_position_type.rb
@@ -7,12 +7,7 @@ module Types
     class DiffPositionType < BaseObject
       graphql_name 'DiffPosition'
 
-      field :head_sha, GraphQL::STRING_TYPE, null: false,
-            description: "The sha of the head at the time the comment was made"
-      field :base_sha,  GraphQL::STRING_TYPE, null: true,
-            description: "The merge base of the branch the comment was made on"
-      field :start_sha, GraphQL::STRING_TYPE, null: false,
-            description: "The sha of the branch being compared against"
+      field :diff_refs, Types::DiffRefsType, null: false
 
       field :file_path, GraphQL::STRING_TYPE, null: false,
             description: "The path of the file that was changed"
diff --git a/app/graphql/types/notes/discussion_type.rb b/app/graphql/types/notes/discussion_type.rb
index c4691942f2d..a3fb28298f6 100644
--- a/app/graphql/types/notes/discussion_type.rb
+++ b/app/graphql/types/notes/discussion_type.rb
@@ -8,8 +8,16 @@ module Types
       authorize :read_note
 
       field :id, GraphQL::ID_TYPE, null: false
+      field :reply_id, GraphQL::ID_TYPE, null: false, description: 'The ID used to reply to this discussion'
       field :created_at, Types::TimeType, null: false
       field :notes, Types::Notes::NoteType.connection_type, null: false, description: "All notes in the discussion"
+
+      # The gem we use to generate Global IDs is hard-coded to work with
+      # `id` properties. To generate a GID for the `reply_id` property,
+      # we must use the ::Gitlab::GlobalId module.
+      def reply_id
+        ::Gitlab::GlobalId.build(object, id: object.reply_id)
+      end
     end
   end
 end