Add a minimal GraphQL API

10 files changed, 256 insertions, 0 deletions

diff --git a/app/graphql/gitlab_schema.rb b/app/graphql/gitlab_schema.rb
new file mode 100644
index 00000000000..7392bf6f503
--- /dev/null
+++ b/app/graphql/gitlab_schema.rb
@@ -0,0 +1,11 @@
+Gitlab::Graphql::Authorize.register!
+
+GitlabSchema = GraphQL::Schema.define do
+  use GraphQL::Batch
+
+  enable_preloading
+  enable_authorization
+
+  mutation(Types::MutationType)
+  query(Types::QueryType)
+end
diff --git a/app/graphql/loaders/base_loader.rb b/app/graphql/loaders/base_loader.rb
new file mode 100644
index 00000000000..c32c4daa91a
--- /dev/null
+++ b/app/graphql/loaders/base_loader.rb
@@ -0,0 +1,24 @@
+# Helper methods for all loaders
+class Loaders::BaseLoader < GraphQL::Batch::Loader
+  # Convert a class method into a resolver proc. The method should follow the
+  # (obj, args, ctx) calling convention
+  class << self
+    def [](sym)
+      resolver = method(sym)
+      raise ArgumentError.new("#{self}.#{sym} is not a resolver") unless resolver.arity == 3
+
+      resolver
+    end
+  end
+
+  # Fulfill all keys. Pass a block that converts each result into a key.
+  # Any keys not in results will be fulfilled with nil.
+  def fulfill_all(results, keys, &key_blk)
+    results.each do |result|
+      key = yield result
+      fulfill(key, result)
+    end
+
+    keys.each { |key| fulfill(key, nil) unless fulfilled?(key) }
+  end
+end
diff --git a/app/graphql/loaders/full_path_loader.rb b/app/graphql/loaders/full_path_loader.rb
new file mode 100644
index 00000000000..f99b487ce5d
--- /dev/null
+++ b/app/graphql/loaders/full_path_loader.rb
@@ -0,0 +1,23 @@
+class Loaders::FullPathLoader < Loaders::BaseLoader
+  class << self
+    def project(obj, args, ctx)
+      project_by_full_path(args[:full_path])
+    end
+
+    def project_by_full_path(full_path)
+      self.for(Project).load(full_path)
+    end
+  end
+
+  attr_reader :model
+
+  def initialize(model)
+    @model = model
+  end
+
+  def perform(keys)
+    # `with_route` prevents relation.all.map(&:full_path)` from being N+1
+    relation = model.where_full_path_in(keys).with_route
+    fulfill_all(relation, keys, &:full_path)
+  end
+end
diff --git a/app/graphql/loaders/iid_loader.rb b/app/graphql/loaders/iid_loader.rb
new file mode 100644
index 00000000000..e89031da0c2
--- /dev/null
+++ b/app/graphql/loaders/iid_loader.rb
@@ -0,0 +1,35 @@
+class Loaders::IidLoader < Loaders::BaseLoader
+  class << self
+    def merge_request(obj, args, ctx)
+      iid = args[:iid]
+      promise = Loaders::FullPathLoader.project_by_full_path(args[:project])
+
+      promise.then do |project|
+        if project
+          merge_request_by_project_and_iid(project.id, iid)
+        else
+          nil
+        end
+      end
+    end
+
+    def merge_request_by_project_and_iid(project_id, iid)
+      self.for(MergeRequest, target_project_id: project_id.to_s).load(iid.to_s)
+    end
+  end
+
+  attr_reader :model, :restrictions
+
+  def initialize(model, restrictions = {})
+    @model = model
+    @restrictions = restrictions
+  end
+
+  def perform(keys)
+    relation = model.where(iid: keys)
+    relation = relation.where(restrictions) if restrictions.present?
+
+    # IIDs are represented as the GraphQL `id` type, which is a string
+    fulfill_all(relation, keys) { |instance| instance.iid.to_s }
+  end
+end
diff --git a/app/graphql/mutations/.keep b/app/graphql/mutations/.keep
new file mode 100644
index 00000000000..e69de29bb2d
--- /dev/null
+++ b/app/graphql/mutations/.keep
diff --git a/app/graphql/types/merge_request_type.rb b/app/graphql/types/merge_request_type.rb
new file mode 100644
index 00000000000..9b12f6f2bf3
--- /dev/null
+++ b/app/graphql/types/merge_request_type.rb
@@ -0,0 +1,50 @@
+Types::MergeRequestType = GraphQL::ObjectType.define do
+  name 'MergeRequest'
+
+  field :id, !types.ID
+  field :iid, !types.ID
+  field :title, types.String
+  field :description, types.String
+  field :state, types.String
+
+  field :created_at, Types::TimeType
+  field :updated_at, Types::TimeType
+
+  field :source_project, -> { Types::ProjectType }
+  field :target_project, -> { Types::ProjectType }
+
+  # Alias for target_project
+  field :project, -> { Types::ProjectType }
+
+  field :source_project_id, types.Int
+  field :target_project_id, types.Int
+  field :project_id, types.Int
+
+  field :source_branch, types.String
+  field :target_branch, types.String
+
+  field :work_in_progress, types.Boolean, property: :work_in_progress?
+  field :merge_when_pipeline_succeeds, types.Boolean
+
+  field :sha, types.String, property: :diff_head_sha
+  field :merge_commit_sha, types.String
+
+  field :user_notes_count, types.Int
+  field :should_remove_source_branch, types.Boolean, property: :should_remove_source_branch?
+  field :force_remove_source_branch, types.Boolean, property: :force_remove_source_branch?
+
+  field :merge_status, types.String
+
+  field :web_url, types.String do
+    resolve ->(merge_request, args, ctx) { Gitlab::UrlBuilder.build(merge_request) }
+  end
+
+  field :upvotes, types.Int
+  field :downvotes, types.Int
+
+  field :subscribed, types.Boolean do
+    resolve ->(merge_request, args, ctx) do
+      merge_request.subscribed?(ctx[:current_user], merge_request.target_project)
+    end
+  end
+end
diff --git a/app/graphql/types/mutation_type.rb b/app/graphql/types/mutation_type.rb
new file mode 100644
index 00000000000..c5061f10239
--- /dev/null
+++ b/app/graphql/types/mutation_type.rb
@@ -0,0 +1,5 @@
+Types::MutationType = GraphQL::ObjectType.define do
+  name "Mutation"
+
+  # TODO: Add Mutations as fields
+end
diff --git a/app/graphql/types/project_type.rb b/app/graphql/types/project_type.rb
new file mode 100644
index 00000000000..bfefc594896
--- /dev/null
+++ b/app/graphql/types/project_type.rb
@@ -0,0 +1,62 @@
+Types::ProjectType = GraphQL::ObjectType.define do
+  name 'Project'
+
+  field :id, !types.ID
+
+  field :full_path, !types.ID
+  field :path, !types.String
+
+  field :name_with_namespace, !types.String
+  field :name, !types.String
+
+  field :description, types.String
+
+  field :default_branch, types.String
+  field :tag_list, types.String
+
+  field :ssh_url_to_repo, types.String
+  field :http_url_to_repo, types.String
+  field :web_url, types.String
+
+  field :star_count, !types.Int
+  field :forks_count, !types.Int
+
+  field :created_at, Types::TimeType
+  field :last_activity_at, Types::TimeType
+
+  field :archived, types.Boolean
+
+  field :visibility, types.String
+
+  field :container_registry_enabled, types.Boolean
+  field :shared_runners_enabled, types.Boolean
+  field :lfs_enabled, types.Boolean
+
+  field :avatar_url, types.String do
+    resolve ->(project, args, ctx) { project.avatar_url(only_path: false) }
+  end
+
+  %i[issues merge_requests wiki snippets].each do |feature|
+    field "#{feature}_enabled", types.Boolean do
+      resolve ->(project, args, ctx) { project.feature_available?(feature, ctx[:current_user]) }
+    end
+  end
+
+  field :jobs_enabled, types.Boolean do
+    resolve ->(project, args, ctx) { project.feature_available?(:builds, ctx[:current_user]) }
+  end
+
+  field :public_jobs, types.Boolean, property: :public_builds
+
+  field :open_issues_count, types.Int do
+    resolve ->(project, args, ctx) { project.open_issues_count if project.feature_available?(:issues, ctx[:current_user]) }
+  end
+
+  field :import_status, types.String
+  field :ci_config_path, types.String
+
+  field :only_allow_merge_if_pipeline_succeeds, types.Boolean
+  field :request_access_enabled, types.Boolean
+  field :only_allow_merge_if_all_discussions_are_resolved, types.Boolean
+  field :printing_merge_request_link_enabled, types.Boolean
+end
diff --git a/app/graphql/types/query_type.rb b/app/graphql/types/query_type.rb
new file mode 100644
index 00000000000..029bbd098ad
--- /dev/null
+++ b/app/graphql/types/query_type.rb
@@ -0,0 +1,38 @@
+Types::QueryType = GraphQL::ObjectType.define do
+  name 'Query'
+
+  field :project, Types::ProjectType do
+    argument :full_path, !types.ID do
+      description 'The full path of the project, e.g., "gitlab-org/gitlab-ce"'
+    end
+
+    authorize :read_project
+
+    resolve Loaders::FullPathLoader[:project]
+  end
+
+  field :merge_request, Types::MergeRequestType do
+    argument :project, !types.ID do
+      description 'The full path of the target project, e.g., "gitlab-org/gitlab-ce"'
+    end
+
+    argument :iid, !types.ID do
+      description 'The IID of the merge request, e.g., "1"'
+    end
+
+    authorize :read_merge_request
+
+    resolve Loaders::IidLoader[:merge_request]
+  end
+
+  # Testing endpoint to validate the API with
+  field :echo, types.String do
+    argument :text, types.String
+
+    resolve -> (obj, args, ctx) do
+      username = ctx[:current_user]&.username
+
+      "#{username.inspect} says: #{args[:text]}"
+    end
+  end
+end
diff --git a/app/graphql/types/time_type.rb b/app/graphql/types/time_type.rb
new file mode 100644
index 00000000000..fb717eb3dc7
--- /dev/null
+++ b/app/graphql/types/time_type.rb
@@ -0,0 +1,8 @@
+# Taken from http://www.rubydoc.info/github/rmosolgo/graphql-ruby/GraphQL/ScalarType
+Types::TimeType = GraphQL::ScalarType.define do
+  name 'Time'
+  description 'Time since epoch in fractional seconds'
+
+  coerce_input ->(value, ctx) { Time.at(Float(value)) }
+  coerce_result ->(value, ctx) { value.to_f }
+end