class Hash
  def deep_symbolize_keys
    inject({}) { |result, (key, value)|
      result[(key.to_sym rescue key) || key] = case value
      when Array
        value.map { |value| value.is_a?(Hash) ? value.deep_symbolize_keys : value }
      when Hash
        value.deep_symbolize_keys
      else
        value
      end
      result
    }
  end unless Hash.method_defined?(:deep_symbolize_keys)
end