Expose comments on Noteables in GraphQL

This exposes `Note`s on Issues & MergeRequests using a
`Types::Notes::NoteableType` in GraphQL.

Exposing notes on a new type can be done by implementing the
`NoteableType` interface on the type. The presented object should
be a `Noteable`.

5 files changed, 145 insertions, 0 deletions

diff --git a/app/graphql/types/notes/diff_position_type.rb b/app/graphql/types/notes/diff_position_type.rb
new file mode 100644
index 00000000000..104ccb79bbb
--- /dev/null
+++ b/app/graphql/types/notes/diff_position_type.rb
@@ -0,0 +1,46 @@
+# frozen_string_literal: true
+
+module Types
+  module Notes
+    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 :file_path, GraphQL::STRING_TYPE, null: false,
+            description: "The path of the file that was changed"
+      field :old_path, GraphQL::STRING_TYPE, null: true,
+            description: "The path of the file on the start sha."
+      field :new_path, GraphQL::STRING_TYPE, null: true,
+            description: "The path of the file on the head sha."
+      field :position_type, Types::Notes::PositionTypeEnum, null: false
+
+      # Fields for text positions
+      field :old_line, GraphQL::INT_TYPE, null: true,
+            description: "The line on start sha that was changed",
+            resolve: -> (position, _args, _ctx) { position.old_line if position.on_text? }
+      field :new_line, GraphQL::INT_TYPE, null: true,
+            description: "The line on head sha that was changed",
+            resolve: -> (position, _args, _ctx) { position.new_line if position.on_text? }
+
+      # Fields for image positions
+      field :x, GraphQL::INT_TYPE, null: true,
+            description: "The X postion on which the comment was made",
+            resolve: -> (position, _args, _ctx) { position.x if position.on_image? }
+      field :y, GraphQL::INT_TYPE, null: true,
+            description: "The Y position on which the comment was made",
+            resolve: -> (position, _args, _ctx) { position.y if position.on_image? }
+      field :width, GraphQL::INT_TYPE, null: true,
+            description: "The total width of the image",
+            resolve: -> (position, _args, _ctx) { position.width if position.on_image? }
+      field :height, GraphQL::INT_TYPE, null: true,
+            description: "The total height of the image",
+            resolve: -> (position, _args, _ctx) { position.height if position.on_image? }
+    end
+  end
+end
diff --git a/app/graphql/types/notes/discussion_type.rb b/app/graphql/types/notes/discussion_type.rb
new file mode 100644
index 00000000000..c4691942f2d
--- /dev/null
+++ b/app/graphql/types/notes/discussion_type.rb
@@ -0,0 +1,15 @@
+# frozen_string_literal: true
+
+module Types
+  module Notes
+    class DiscussionType < BaseObject
+      graphql_name 'Discussion'
+
+      authorize :read_note
+
+      field :id, GraphQL::ID_TYPE, null: false
+      field :created_at, Types::TimeType, null: false
+      field :notes, Types::Notes::NoteType.connection_type, null: false, description: "All notes in the discussion"
+    end
+  end
+end
diff --git a/app/graphql/types/notes/note_type.rb b/app/graphql/types/notes/note_type.rb
new file mode 100644
index 00000000000..85c55d16ac2
--- /dev/null
+++ b/app/graphql/types/notes/note_type.rb
@@ -0,0 +1,46 @@
+# frozen_string_literal: true
+
+module Types
+  module Notes
+    class NoteType < BaseObject
+      graphql_name 'Note'
+
+      authorize :read_note
+
+      expose_permissions Types::PermissionTypes::Note
+
+      field :id, GraphQL::ID_TYPE, null: false
+
+      field :project, Types::ProjectType,
+            null: true,
+            description: "The project this note is associated to",
+            resolve: -> (note, args, context) { Gitlab::Graphql::Loaders::BatchModelLoader.new(Project, note.project_id).find }
+
+      field :author, Types::UserType,
+            null: false,
+            description: "The user who wrote this note",
+            resolve: -> (note, args, context) { Gitlab::Graphql::Loaders::BatchModelLoader.new(User, note.author_id).find }
+
+      field :resolved_by, Types::UserType,
+            null: true,
+            description: "The user that resolved the discussion",
+            resolve: -> (note, _args, _context) { Gitlab::Graphql::Loaders::BatchModelLoader.new(User, note.resolved_by_id).find }
+
+      field :system, GraphQL::BOOLEAN_TYPE,
+            null: false,
+            description: "Whether or not this note was created by the system or by a user"
+
+      field :body, GraphQL::STRING_TYPE,
+            null: false,
+            method: :note,
+            description: "The content note itself"
+
+      field :created_at, Types::TimeType, null: false
+      field :updated_at, Types::TimeType, null: false
+      field :discussion, Types::Notes::DiscussionType, null: true, description: "The discussion this note is a part of"
+      field :resolvable, GraphQL::BOOLEAN_TYPE, null: false, method: :resolvable?
+      field :resolved_at, Types::TimeType, null: true, description: "The time the discussion was resolved"
+      field :position, Types::Notes::DiffPositionType, null: true, description: "The position of this note on a diff"
+    end
+  end
+end
diff --git a/app/graphql/types/notes/noteable_type.rb b/app/graphql/types/notes/noteable_type.rb
new file mode 100644
index 00000000000..9f126d67b0d
--- /dev/null
+++ b/app/graphql/types/notes/noteable_type.rb
@@ -0,0 +1,25 @@
+# frozen_string_literal: true
+
+module Types
+  module Notes
+    module NoteableType
+      include Types::BaseInterface
+
+      field :notes, Types::Notes::NoteType.connection_type, null: false, description: "All notes on this noteable"
+      field :discussions, Types::Notes::DiscussionType.connection_type, null: false, description: "All discussions on this noteable"
+
+      definition_methods do
+        def resolve_type(object, context)
+          case object
+          when Issue
+            Types::IssueType
+          when MergeRequest
+            Types::MergeRequestType
+          else
+            raise "Unknown GraphQL type for #{object}"
+          end
+        end
+      end
+    end
+  end
+end
diff --git a/app/graphql/types/notes/position_type_enum.rb b/app/graphql/types/notes/position_type_enum.rb
new file mode 100644
index 00000000000..abdb2cfc804
--- /dev/null
+++ b/app/graphql/types/notes/position_type_enum.rb
@@ -0,0 +1,13 @@
+# frozen_string_literal: true
+
+module Types
+  module Notes
+    class PositionTypeEnum < BaseEnum
+      graphql_name 'DiffPositionType'
+      description 'Type of file the position refers to'
+
+      value 'text'
+      value 'image'
+    end
+  end
+end