class GraphQL::Schema::Union

def assert_valid_union_member(type_defn)
  if type_defn.is_a?(Module) && !type_defn.is_a?(Class)
    # it's an interface type, defined as a module
    raise ArgumentError, "Union possible_types can only be object types (not interface types), remove #{type_defn.graphql_name} (#{type_defn.inspect})"
  end
end

def assign_type_membership_object_type(object_type)
  assert_valid_union_member(object_type)
  type_memberships.each { |tm|
    possible_type = tm.object_type
    if possible_type.is_a?(String) && (possible_type == object_type.name)
      # This is a match of Ruby class names, not graphql names,
      # since strings are used to refer to constants.
      tm.object_type = object_type
    elsif possible_type.is_a?(LateBoundType) && possible_type.graphql_name == object_type.graphql_name
      tm.object_type = object_type
    end
  }
  nil
end

def inherited(child_class)
  add_unresolved_type_error(child_class)
  super
end

def kind
  GraphQL::TypeKinds::UNION
end

def possible_types(*types, context: GraphQL::Query::NullContext, **options)
  if types.any?
    types.each do |t|
      assert_valid_union_member(t)
      type_memberships << type_membership_class.new(self, t, **options)
    end
  else
    visible_types = []
    type_memberships.each do |type_membership|
      if type_membership.visible?(context)
        visible_types << type_membership.object_type
      end
    end
    visible_types
  end
end

def to_graphql
  type_defn = GraphQL::UnionType.new
  type_defn.name = graphql_name
  type_defn.description = description
  type_defn.ast_node = ast_node
  type_defn.type_memberships = type_memberships
  if respond_to?(:resolve_type)
    type_defn.resolve_type = method(:resolve_type)
  end
  type_defn.metadata[:type_class] = self
  type_defn
end

def type_membership_class(membership_class = nil)
  if membership_class
    @type_membership_class = membership_class
  else
    @type_membership_class || find_inherited_value(:type_membership_class, GraphQL::Schema::TypeMembership)
  end
end

def type_memberships
  @type_memberships ||= []
end