decode_pesel.rb

#!ruby

pesel = ARGV[0]
puts pesel
puts pesel[2]
puts pesel[0..1]
if /^[0-9]{11}/.match(pesel)
	case pesel[2].to_i # first digit of month number encodes century
	when 8, 9
		century = 1800
		month = pesel[2..3].to_i - 80
	when 0, 1
		century = 1900
		month = pesel[2..3].to_i
	when 2, 3
		century = 2000
		month = pesel[2..3].to_i - 20
	when 4, 5
		century = 2100
		month = pesel[2..3].to_i - 40
	when 6, 7
		century = 2200
		month = pesel[2..3].to_i - 60
	end
	year = century + pesel[0..1].to_i
	day = pesel[4..5].to_i
	gender = pesel[9].to_i.even? ? 0 : 1
	control_digit_given = pesel[10].to_i
	factors_array = [9, 7, 3, 1, 9, 7, 3, 1, 9, 7] # for control digit calculation
	control_digit_calculated = 0
	pesel[0..9].split('').map.with_index{|digit, index| control_digit_calculated += digit.to_i * factors_array[index]}
	control_digit_calculated %= 10

	puts year
	puts month
	puts day
	puts gender
	puts control_digit_given
	puts control_digit_calculated
else
	puts 'error!'
end