Short Code Generator

short_code_generator.rb

require "digest/md5"

module App
  module Tools
    class ShortCodeGenerator

      attr_reader :max_code_length
      def initialize(max_code_length)
        if max_code_length < 2
          raise "Code length needs to be a value of AT LEAST '2'!"
        end
        @max_code_length = max_code_length
      end

      def create(object_id)
        url36 = Digest::MD5.hexdigest(object_id.to_s + SALT).slice(0..@max_code_length)

        base62 = ['0'..'9','A'..'Z','a'..'z'].map{|a| a.to_a}.flatten
        base36 = {};['0'..'9','a'..'z'].map{|range| range.to_a}.flatten.each_with_index{|char, position| base36[char] = position}
        url62, url10 = "",0

        # convert to base10
        url36.reverse.chars.to_a.each_with_index { |c,i| url10 += base36[c] * (36 ** i)}

        # convert to base62
        @max_code_length.times{|i| url62 << base62[url10 % 62]; url10 = url10 / 62}

        url62
      end

      private

      SALT = "YeFrugehacuasdfasdfasdfuxu$-Faspawazasay*me$EcaruS?at@uwrejaw$nuz"

    end
  end
end