module Amka

# File lib/amka.rb, line 16
def self.generate(date_of_birth = nil)
  return generate_with_date_of_birth(date_of_birth) unless date_of_birth.nil?

  date_6_digits = ''
  loop do
    day = rand(0..3).to_s << rand(0..9).to_s
    next if day == '00' || day.to_i > 31
    month = rand(0..1).to_s << rand(0..2).to_s
    next if month == '00' || month.to_i > 12
    year = rand(19..20).to_s << rand(0..9).to_s << rand(0..9).to_s
    next if year.to_i > Date.today.year

    if Utils.valid_date?(date = day << month << year[2..3], year)
      date_6_digits = date
      break
    end
  end

  Luhn.generate(11, date_6_digits)
end

# File lib/amka.rb, line 6
def self.valid?(amka, year = nil)
  Utils.string_with_digits_or_fail amka

  return false unless length_is_11?(amka)

  return Luhn.valid?(amka) if Utils.valid_date?(amka, year)

  false
end

# File lib/amka.rb, line 37
def self.generate_with_date_of_birth(date_of_birth)
  Utils.string_with_date_or_fail date_of_birth

  day, month, year = date_of_birth.split('/').map { |i| i.length == 1 && ('0' << i) or i }
  date_6_digit = day << month << year[2..3]
  fail ArgumentError, 'The date of birth is invalid!' unless Utils.valid_date?(date_6_digit, year)

  Luhn.generate(11, date_6_digit)
end

# File lib/amka.rb, line 48
def self.length_is_11?(id)
  id.length == 11
end