snaky.rb

require 'active_support/core_ext/string/inflections'
require 'active_support/core_ext/hash/indifferent_access'

module Snaky
  refine Hash do
    def to_snake_case(value = self)
      case value
      when Hash
        value.map { |k, v| [k.underscore, to_snake_case(v)] }.to_h.with_indifferent_access
      when Array
        value.map { |v| to_snake_case(v) }
      else
        value
      end
    end
  end
end