class SimpleForm::Inputs::GroupedCollectionSelectInput

def collection
  @collection ||= grouped_collection.map { |collection| group_method.respond_to?(:call) ? group_method.call(collection) : collection.try(:send, group_method) }.detect(&:present?) || []
end

def detect_method_from_class(collection_classes)
  return {} if collection_classes.empty?
  sample = collection_classes.first
  { label: SimpleForm.collection_label_methods.find { |m| sample.instance_methods.include?(m) },
    value: SimpleForm.collection_value_methods.find { |m| sample.instance_methods.include?(m) } }
end

def group_label_method
  label = options.delete(:group_label_method)
  unless label
    common_method_for = detect_common_display_methods(detect_collection_classes(grouped_collection))
    label = common_method_for[:label]
  end
  label
end

def group_method
  @group_method ||= options.delete(:group_method)
end

def grouped_collection
  @grouped_collection ||= begin
    grouped_collection = options.delete(:collection)
    grouped_collection.respond_to?(:call) ? grouped_collection.call : grouped_collection.to_a
  end
end

def input(wrapper_options = nil)
  label_method, value_method = detect_collection_methods
  merged_input_options = merge_wrapper_options(input_html_options, wrapper_options)
  @builder.grouped_collection_select(attribute_name, grouped_collection,
                group_method, group_label_method, value_method, label_method,
                input_options, merged_input_options)
end