Paper Fortune

paperfortune.rb

# -*- coding: utf-8 -*-

require 'date'
require 'digest/sha1'

module PaperFortune
  def self.paper_fortune(w, *a)
    n = w.inject(&:+)
    r = Random.new(Digest::SHA1.hexdigest(Marshal.dump(a)).to_i(16)).rand(n)
    w.each_index.find {|i| r < w[0..i].inject(&:+) }
  end
end

japanese = [
  '大吉',
  '中吉',
  '小吉',
  '吉',
  '半吉',
  '末吉',
  '末小吉',
  '凶',
  '小凶',
  '半凶',
  '末凶',
  '大凶',
]
weights = [ 3, 5, 7, 10, 10, 15, 15, 10, 10, 7, 5, 3 ]

name = 'mono0x'
p name, japanese[PaperFortune.paper_fortune(weights, Date.today, name)]