require 'base64'

module RightSupport::Data
  # Implements the base64url encoding mechanism as described in RFC7515: JSON
  # Web Signature (JWS).
  #
  # This encoding is similar to base64, but omits newlines and padding
  # `=` characters, and uses the `-` and `_` characters in place of the `+` and
  # `/` characters. This makes it suitable for use inside URLs, cookies, and
  # other "webby" contexts where we want to avoid text expansion due to URL
  # encoding.
  module Base64URL
    # @param [String] str ASCII string to encode
    # @return [String] base64 representation of str
    def self.encode(text)
      Base64.encode64(text).tr('+/', '-_').gsub(/[\n=]/, '')
    end

    # @param [String] str base64 to decode to ASCII
    # @return [String] plain ASCII
    def self.decode(b64)
      b64 = b64.dup
      b64 += '=' * (4 - b64.length.modulo(4))
      Base64.decode64(b64.tr('-_', '+/'))
    end
  end
end