module Graphiti
  module Adapters
    class GraphitiAPI < ::Graphiti::Adapters::Null
      def base_scope(model)
        {}
      end

      def resolve(scope)
        url = build_url(scope)
        response = resource.make_request(url)
        json = JSON.parse(response.body)

        if json['errors']
          handle_remote_error(url, json)
        else
          models = json['data'].map { |d| build_entity(json, d) }
          Util::RemoteSerializer.for(resource.class.serializer, models)
          models
        end
      end

      private

      def handle_remote_error(url, json)
        errors = json['errors'].map do |error|
          if raw = error['meta'].try(:[], '__raw_error__')
            { message: raw['message'], backtrace: raw['backtrace'] }
          else
            { message: "#{error['title']} - #{error['detail']}" }
          end
        end.compact
        raise Errors::Remote.new(url, errors)
      end

      def build_url(scope)
        url = resource.remote_url
        params = scope[:params].merge(scope.except(:params))
        params = CGI.unescape(params.to_query)
        url = "#{url}?#{params}" unless params.blank?
        url
      end

      def find_entity(json, id, type)
        lookup = Array(json['data']) | Array(json['included'])
        lookup.find { |l| l['id'] == id.to_s && l['type'] == type }
      end

      def build_entity(json, node)
        entity = OpenStruct.new(node['attributes'])
        entity.id = node['id']
        entity._type = node['type']
        process_relationships(entity, json, node['relationships'] || {})
        entity
      end

      def process_relationships(entity, json, relationship_json)
        entity._relationships = {}
        relationship_json.each_pair do |name, hash|
          if data = hash['data']
            if data.is_a?(Array)
              data.each do |d|
                rel = find_entity(json, d['id'], d['type'])
                related_entity = build_entity(json, rel)
                add_relationship(entity, related_entity, name, true)
              end
            else
              rel = find_entity(json, hash['data']['id'], hash['data']['type'])
              related_entity = build_entity(json, rel)
              add_relationship(entity, related_entity, name)
            end
          end
          Util::RemoteSerializer.for(Graphiti::Serializer, Array(entity[name]))
        end
      end

      def add_relationship(entity, related_entity, name, many = false)
        if many
          entity[name] ||= []
          entity[name] << related_entity
          entity._relationships[name] ||= []
          entity._relationships[name] << related_entity
        else
          entity[name] = related_entity
          entity._relationships[name] = related_entity
        end
      end
    end
  end
end