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+# GraphQL API
+
+## Authentication
+
+Authentication happens through the `GraphqlController`, right now this
+uses the same authentication as the Rails application. So the session
+can be shared.
+
+It is also possible to add a `private_token` to the querystring, or
+add a `HTTP_PRIVATE_TOKEN` header.
+
+### Authorization
+
+Fields can be authorized using the same abilities used in the Rails
+app. This can be done using the `authorize` helper:
+
+```ruby
+module Types
+  class QueryType < BaseObject
+    graphql_name 'Query'
+
+    field :project, Types::ProjectType, null: true, resolver: Resolvers::ProjectResolver do
+      authorize :read_project
+    end
+  end
+```
+
+The object found by the resolve call is used for authorization.
+
+This works for authorizing a single record, for authorizing
+collections, we should only load what the currently authenticated user
+is allowed to view. Preferably we use our existing finders for that.
+
+## Types
+
+When exposing a model through the GraphQL API, we do so by creating a
+new type in `app/graphql/types`.
+
+When exposing properties in a type, make sure to keep the logic inside
+the definition as minimal as possible. Instead, consider moving any
+logic into a presenter:
+
+```ruby
+class Types::MergeRequestType < BaseObject
+  present_using MergeRequestPresenter
+
+  name 'MergeRequest'
+end
+```
+
+An existing presenter could be used, but it is also possible to create
+a new presenter specifically for GraphQL.
+
+The presenter is initialized using the object resolved by a field, and
+the context.
+
+## Resolvers
+
+To find objects to display in a field, we can add resolvers to
+`app/graphql/resolvers`.
+
+Arguments can be defined within the resolver, those arguments will be
+made available to the fields using the resolver.
+
+We already have a `FullPathLoader` that can be included in other
+resolvers to quickly find Projects and Namespaces which will have a
+lot of dependant objects.
+
+To limit the amount of queries performed, we can use `BatchLoader`.
+
+## Testing
+
+_full stack_ tests for a graphql query or mutation live in
+`spec/requests/api/graphql`.
+
+When adding a query, the `a working graphql query` shared example can
+be used to test if the query renders valid results.
+
+Using the `GraphqlHelpers#all_graphql_fields_for`-helper, a query
+including all available fields can be constructed. This makes it easy
+to add a test rendering all possible fields for a query.