class ActiveSupport::Messages::RotationCoordinator

def [](salt)
  @codecs[salt] ||= build_with_rotations(salt)
end

def []=(salt, codec)
  @codecs[salt] = codec
end

def build(salt, secret_generator:, secret_generator_options:, **options)
  raise NotImplementedError
end

def build_with_rotations(salt)
  rotate_options = @rotate_options.map { |options| options.is_a?(Proc) ? options.(salt) : options }
  transitional = self.transitional && rotate_options.first
  rotate_options.compact!
  rotate_options[0..1] = rotate_options[0..1].reverse if transitional
  rotate_options = rotate_options.map { |options| normalize_options(options) }.uniq
  raise "No options have been configured for #{salt}" if rotate_options.empty?
  rotate_options.map { |options| build(salt.to_s, **options) }.reduce(&:fall_back_to)
end

def changing_configuration!
  if @codecs.any?
    raise <<~MESSAGE
      Cannot change #{self.class} configuration after it has already been applied.
      The configuration has been applied with the following salts:
      #{@codecs.keys.map { |salt| "- #{salt.inspect}" }.join("\n")}
    MESSAGE
  end
end

def clear_rotations
  changing_configuration!
  @rotate_options.clear
  self
end

def initialize(&secret_generator)
  raise ArgumentError, "A secret generator block is required" unless secret_generator
  @secret_generator = secret_generator
  @rotate_options = []
  @on_rotation = nil
  @codecs = {}
end

def normalize_options(options)
  options = options.dup
  options[:secret_generator] ||= @secret_generator
  secret_generator_kwargs = options[:secret_generator].parameters.
    filter_map { |type, name| name if type == :key || type == :keyreq }
  options[:secret_generator_options] = options.extract!(*secret_generator_kwargs)
  options[:on_rotation] = @on_rotation
  options
end

def on_rotation(&callback)
  changing_configuration!
  @on_rotation = callback
end

def rotate(**options, &block)
  raise ArgumentError, "Options cannot be specified when using a block" if block && !options.empty?
  changing_configuration!
  @rotate_options << (block || options)
  self
end

def rotate_defaults
  rotate()
end