module GraphQL::Schema::Resolver::HasPayloadType

def field(*args, **kwargs, &block)
  pt = payload_type # make sure it's initialized with any inherited fields
  field_defn = super
  # Remove any inherited fields to avoid false conflicts at runtime
  prev_fields = pt.own_fields[field_defn.graphql_name]
  case prev_fields
  when GraphQL::Schema::Field
    if prev_fields.owner != self
      pt.own_fields.delete(field_defn.graphql_name)
    end
  when Array
    prev_fields.reject! { |f| f.owner != self }
    if prev_fields.empty?
      pt.own_fields.delete(field_defn.graphql_name)
    end
  end
  pt.add_field(field_defn, method_conflict_warning: false)
  field_defn
end

def field_class(new_class = nil)
  if new_class
    @field_class = new_class
  elsif defined?(@field_class) && @field_class
    @field_class
  else
    find_inherited_value(:field_class, GraphQL::Schema::Field)
  end
end

def generate_payload_type
  resolver_name = graphql_name
  resolver_fields = all_field_definitions
  pt = Class.new(object_class)
  pt.graphql_name("#{resolver_name}Payload")
  pt.description("Autogenerated return type of #{resolver_name}.")
  resolver_fields.each do |f|
    # Reattach the already-defined field here
    # (The field's `.owner` will still point to the mutation, not the object type, I think)
    # Don't re-warn about a method conflict. Since this type is generated, it should be fixed in the resolver instead.
    pt.add_field(f, method_conflict_warning: false)
  end
  pt
end

def object_class(new_class = nil)
  if new_class
    if defined?(@payload_type)
      raise "Can't configure `object_class(...)` after the payload type has already been initialized. Move this configuration higher up the class definition."
    end
    @object_class = new_class
  else
    @object_class || find_inherited_value(:object_class, GraphQL::Schema::Object)
  end
end

def payload_type(new_payload_type = nil)
  if new_payload_type
    @payload_type = new_payload_type
  end
  @payload_type ||= generate_payload_type
end

def type(new_type = nil, null: nil)
  if new_type
    payload_type(new_type)
    if !null.nil?
      self.null(null)
    end
  else
    super()
  end
end