cache_key.rb

module CacheKey
  extend self

  def expirable(range = :minute, time = ::Time.current)
    key = case range
      when :always
        ::Time.current  
      when :never
        nil
      when :second
        time
      when :minute
        time.change(:sec => 0)
      when :hour
        time.change(:min => 0, :sec => 0)
      when :day
        time.change(:hour => 0, :min => 0, :sec => 0)
      when :month
        time.change(:day => 1, :hour => 0, :min => 0, :sec => 0)
      when :year
        time.change(:month => 1, :day => 1, :hour => 0, :min => 0, :sec => 0)
      else
        raise ArgumentError, "Unsupported expiration range `#{range}'"
    end.to_i
  end
end