Initial setup GraphQL using graphql-ruby 1.8

- All definitions have been replaced by classes:
  http://graphql-ruby.org/schema/class_based_api.html
- Authorization & Presentation have been refactored to work in the
  class based system
- Loaders have been replaced by resolvers
- Times are now coersed as ISO 8601

4 files changed, 55 insertions, 0 deletions

diff --git a/app/graphql/resolvers/base_resolver.rb b/app/graphql/resolvers/base_resolver.rb
new file mode 100644
index 00000000000..89b7f9dad6f
--- /dev/null
+++ b/app/graphql/resolvers/base_resolver.rb
@@ -0,0 +1,4 @@
+module Resolvers
+  class BaseResolver < GraphQL::Schema::Resolver
+  end
+end
diff --git a/app/graphql/resolvers/full_path_resolver.rb b/app/graphql/resolvers/full_path_resolver.rb
new file mode 100644
index 00000000000..4eb28aaed6c
--- /dev/null
+++ b/app/graphql/resolvers/full_path_resolver.rb
@@ -0,0 +1,19 @@
+module Resolvers
+  module FullPathResolver
+    extend ActiveSupport::Concern
+
+    prepended do
+      argument :full_path, GraphQL::ID_TYPE,
+               required: true,
+               description: 'The full path of the project or namespace, e.g., "gitlab-org/gitlab-ce"'
+    end
+
+    def model_by_full_path(model, full_path)
+      BatchLoader.for(full_path).batch(key: "#{model.model_name.param_key}:full_path") do |full_paths, loader|
+        # `with_route` avoids an N+1 calculating full_path
+        results = model.where_full_path_in(full_paths).with_route
+        results.each { |project| loader.call(project.full_path, project) }
+      end
+    end
+  end
+end
diff --git a/app/graphql/resolvers/merge_request_resolver.rb b/app/graphql/resolvers/merge_request_resolver.rb
new file mode 100644
index 00000000000..b1857ab09f7
--- /dev/null
+++ b/app/graphql/resolvers/merge_request_resolver.rb
@@ -0,0 +1,21 @@
+module Resolvers
+  class MergeRequestResolver < BaseResolver
+    prepend FullPathResolver
+
+    type Types::ProjectType, null: true
+
+    argument :iid, GraphQL::ID_TYPE,
+             required: true,
+             description: 'The IID of the merge request, e.g., "1"'
+
+    def resolve(full_path:, iid:)
+      project = model_by_full_path(Project, full_path)
+      return unless project.present?
+
+      BatchLoader.for(iid.to_s).batch(key: project.id) do |iids, loader|
+        results = project.merge_requests.where(iid: iids)
+        results.each { |mr| loader.call(mr.iid.to_s, mr) }
+      end
+    end
+  end
+end
diff --git a/app/graphql/resolvers/project_resolver.rb b/app/graphql/resolvers/project_resolver.rb
new file mode 100644
index 00000000000..ec115bad896
--- /dev/null
+++ b/app/graphql/resolvers/project_resolver.rb
@@ -0,0 +1,11 @@
+module Resolvers
+  class ProjectResolver < BaseResolver
+    prepend FullPathResolver
+
+    type Types::ProjectType, null: true
+
+    def resolve(full_path:)
+      model_by_full_path(Project, full_path)
+    end
+  end
+end