class BinData::DSLMixin::DSLBigAndLittleEndianHandler

def class_with_endian(class_name, endian)
  hints = {
    endian: endian,
    search_prefix: class_name.dsl_parser.search_prefix,
  }
  RegisteredClasses.lookup(class_name, hints)
end

def create_subclasses_with_endian(bnl_class)
  instance_eval "class ::#{bnl_class}Be < ::#{bnl_class}; endian :big; end"
  instance_eval "class ::#{bnl_class}Le < ::#{bnl_class}; endian :little; end"
end

def delegate_field_creation(bnl_class)
  endian_classes = {
    big:    class_with_endian(bnl_class, :big),
    little: class_with_endian(bnl_class, :little),
  }
  parser = bnl_class.dsl_parser
  parser.define_singleton_method(:parse_and_append_field) do |*args, &block|
    endian_classes[:big].send(*args, &block)
    endian_classes[:little].send(*args, &block)
  end
end

def fixup_subclass_hierarchy(bnl_class)
  parent = bnl_class.superclass
  if obj_attribute(parent, :endian) == :big_and_little
    be_subclass = class_with_endian(bnl_class, :big)
    be_parent   = class_with_endian(parent, :big)
    be_fields   = obj_attribute(be_parent, :fields)
    le_subclass = class_with_endian(bnl_class, :little)
    le_parent   = class_with_endian(parent, :little)
    le_fields   = obj_attribute(le_parent, :fields)
    be_subclass.dsl_parser.define_singleton_method(:parent_fields) do
      be_fields
    end
    le_subclass.dsl_parser.define_singleton_method(:parent_fields) do
      le_fields
    end
  end
end

def handle(bnl_class)
  make_class_abstract(bnl_class)
  create_subclasses_with_endian(bnl_class)
  override_new_in_class(bnl_class)
  delegate_field_creation(bnl_class)
  fixup_subclass_hierarchy(bnl_class)
end

def make_class_abstract(bnl_class)
  bnl_class.send(:unregister_self)
end

def obj_attribute(obj, attr)
  obj.dsl_parser.send(attr)
end

def override_new_in_class(bnl_class)
  endian_classes = {
    big:    class_with_endian(bnl_class, :big),
    little: class_with_endian(bnl_class, :little),
  }
  bnl_class.define_singleton_method(:new) do |*args|
    if self == bnl_class
      _, options, _ = arg_processor.separate_args(self, args)
      delegate = endian_classes[options[:endian]]
      return delegate.new(*args) if delegate
    end
    super(*args)
  end
end