Generate periodically unique token.

periodical_token.rb

require 'digest/sha2'

# usage:
# PeriodicalToken.generate(:min) # -> returns unique token in a minute.
#
class PeriodicalToken
  SALT = 'RANDOMLLY-GENERATED-STRING'
  RANGE_TO_DIV = {
      min: 60,
      min5: 60 * 5,
      min15: 60 * 15,
      min30: 60 * 30,
      hour: 60 * 60,
      hour3: 60 * 60 * 3,
      hour6: 60 * 60 * 6,
      hour12: 60 * 60 * 12,
      day: 60 * 60 * 24,
      week: 60 * 60 * 24 * 7
  }
  def self.generate(range = :day)
    value = format_by_range(range)
    Digest::MD5.hexdigest(value + SALT)
  end
  private
  def self.format_by_range(range)
    range = range.to_sym
    now = UTC.now.to_i
    mod = now % RANGE_TO_DIV[range]
    (now - mod).to_s
  end
end