module GraphQL
  # Type kinds are the basic categories which a type may belong to (`Object`, `Scalar`, `Union`...)
  module TypeKinds
    # These objects are singletons, eg `GraphQL::TypeKinds::UNION`, `GraphQL::TypeKinds::SCALAR`.
    class TypeKind
      attr_reader :name
      def initialize(name, resolves: false, fields: false, wraps: false, input: false)
        @name = name
        @resolves = resolves
        @fields = fields
        @wraps = wraps
        @input = input
        @composite = fields? || resolves?
      end

      # Does this TypeKind have multiple possible implementors?
      def resolves?;  @resolves;  end
      # Does this TypeKind have queryable fields?
      def fields?;    @fields;    end
      # Does this TypeKind modify another type?
      def wraps?;     @wraps;     end
      # Is this TypeKind a valid query input?
      def input?;     @input;     end
      def to_s;       @name;      end
      # Is this TypeKind composed of many values?
      def composite?; @composite; end
    end

    TYPE_KINDS = [
      SCALAR =        TypeKind.new("SCALAR", input: true),
      OBJECT =        TypeKind.new("OBJECT", fields: true),
      INTERFACE =     TypeKind.new("INTERFACE", resolves: true, fields: true),
      UNION =         TypeKind.new("UNION", resolves: true),
      ENUM =          TypeKind.new("ENUM", input: true),
      INPUT_OBJECT =  TypeKind.new("INPUT_OBJECT", input: true),
      LIST =          TypeKind.new("LIST", wraps: true),
      NON_NULL =      TypeKind.new("NON_NULL", wraps: true),
    ]

    KIND_NAMES = TYPE_KINDS.map(&:name)
    class TypeKind
      KIND_NAMES.each do |kind_name|
        define_method("#{kind_name.downcase}?") do
          self.name == kind_name
        end
      end
    end
  end
end