Ruby Hash to-from dotted notation hash

gistfile1.rb

class Hash
  def to_dotted_hash(recursive_key = '')
    self.each_with_object({}) do |(k, v), ret|
      key = recursive_key + k.to_s

      if v.is_a?(Hash)
        ret.merge!(v.to_dotted_hash(key + '.'))
      else
        ret[key] = v
      end
    end
  end

  def self.from_dotted_hash(hash, recursive_key = '')
    key_regexp = /\A(\w+)\./

    hash.each_with_object({}) do |(k, v), ret|
      key = k.gsub(/\A#{recursive_key}/, '')

      if key =~ key_regexp
        nested_key = $1
        match_nested_hash = ->(k,_) { k.match(/\A#{nested_key}\./) }

        nested_hash = hash.select(&match_nested_hash)
        ret.delete_if(&match_nested_hash)
        ret.merge!(nested_key => from_dotted_hash(nested_hash, nested_key + '.'))
      else
        ret[key] = v
      end
    end
  end
end