class Faker::Code

def asin
  fetch('code.asin')
end

def ean(base: 13)
  case base
  when 8 then generate_base8_ean
  when 13 then generate_base13_ean
  else raise ArgumentError, 'base must be 8 or 13'
  end
end

def generate_base10_isbn
  generate(:string) do |g|
    g.int(name: :values, length: 9)
    g.lit('-')
    g.computed(name: :checksum, deps: [:values]) do |values|
      remainder = sum(values.to_s) { |value, offset| (offset + 1) * value.to_i } % 11
      if remainder == 10
        'X'
      else
        remainder.to_s
      end
    end
  end
end

def generate_base13_ean
  generate(:string) do |g|
    g.int(name: :values, length: 12)
    g.computed(name: :checksum, deps: [:values]) do |values|
      check_digit = 10 - values.to_s.chars.each_with_index.inject(0) { |s, (v, i)| s + v.to_i * EAN_CHECK_DIGIT13[i] } % 10
      if check_digit == 10
        0
      else
        check_digit
      end
    end
  end
end

def generate_base13_isbn
  generate(:string) do |g|
    g.int(name: :values, length: 12)
    g.lit('-')
    g.computed(name: :checksum, deps: [:values]) do |values|
      remainder = sum(values.to_s) { |value, offset| offset.even? ? value.to_i : value.to_i * 3 } % 10
      (10 - remainder) % 10
    end
  end
end

def generate_base8_ean
  generate(:string) do |g|
    g.int(name: :values, length: 7)
    g.computed(name: :checksum, deps: [:values]) do |values|
      check_digit = 10 - values.to_s.chars.each_with_index.inject(0) { |s, (v, i)| s + v.to_i * EAN_CHECK_DIGIT8[i] } % 10
      if check_digit == 10
        0
      else
        check_digit
      end
    end
  end
end

def generate_imei
  str = Array.new(15, 0)
  sum = 0
  len = 15
  # Fill in the first two values of the string based with the specified prefix.
  # Reporting Body Identifier list: http://en.wikipedia.org/wiki/Reporting_Body_Identifier
  arr = sample(RBI)
  str[0] = arr[0].to_i
  str[1] = arr[1].to_i
  pos = 2
  # Fill all the remaining numbers except for the last one with random values.
  while pos < (len - 1)
    str[pos] = rand(0..9)
    pos += 1
  end
  # Calculate the Luhn checksum of the values thus far
  len_offset = (len + 1) % 2
  (0..(len - 1)).each do |position|
    if (position + len_offset).odd?
      t = str[position] * 2
      t -= 9 if t > 9
      sum += t
    else
      sum += str[position]
    end
  end
  # Choose the last digit so that it causes the entire string to pass the checksum.
  str[len - 1] = (10 - (sum % 10)) % 10
  # Output the IMEI value.
  str.join
end

def generate_nric_check_alphabet(values, prefix)
  weight = %w[2 7 6 5 4 3 2]
  total = values.chars.zip(weight).collect { |a, b| a.to_i * b.to_i }.inject(:+)
  total += 4 if prefix == 'T'
  %w[A B C D E F G H I Z J][10 - total % 11]
end

def generate_sin_check_digit(digits)
  # Fast Luhn checksum code from luhn.js:
  # https://gist.github.com/ShirtlessKirk/2134376
  len = 9
  mul = 0
  luhn_arr = [
    [0, 1, 2, 3, 4, 5, 6, 7, 8, 9],
    [0, 2, 4, 6, 8, 1, 3, 5, 7, 9]
  ]
  sum = 0
  while len.positive?
    len -= 1
    num = digits[len].to_i
    sum += luhn_arr[mul][num]
    mul ^= 1
  end
  checksum = sum % 10
  checksum.zero? ? checksum : (10 - checksum)
end

def imei
  generate_imei
end

def isbn(base: 10)
  case base
  when 10 then generate_base10_isbn
  when 13 then generate_base13_isbn
  else raise ArgumentError, 'base must be 10 or 13'
  end
end

def npi
  rand(10**10).to_s.rjust(10, '0')
end

def nric(min_age: 18, max_age: 65)
  birthyear = Date.birthday(min_age: min_age, max_age: max_age).year
  generate(:string) do |g|
    g.computed(name: :prefix) do
      if birthyear < 2000
        'S'
      else
        'T'
      end
    end
    g.computed(name: :yy) do
      birthyear.to_s[-2..]
    end
    g.int(name: :values, length: 5)
    g.computed(name: :check, deps: %i[prefix yy values]) do |prefix, yy, values|
      generate_nric_check_alphabet("#{yy}#{values}", prefix)
    end
  end
end

def rut
  value = Number.number(digits: 8).to_s
  vd = rut_verificator_digit(value)
  value << "-#{vd}"
end

def rut_verificator_digit(rut)
  total = rut.to_s.rjust(8, '0').chars.zip(%w[3 2 7 6 5 4 3 2]).collect { |a, b| a.to_i * b.to_i }.inject(:+)
  (11 - total % 11).to_s.gsub('10', 'k').gsub('11', '0')
end

def sin
  # 1   - province or temporary resident
  # 2-8 - random numbers
  # 9   - checksum
  # 1st digit. 8,0 are not used
  registry = Faker::Base.sample([1, 2, 3, 4, 5, 6, 7, 9]).to_s
  # generate 2nd to 8th
  partial = Array.new(7) { Faker::Config.random.rand(0..9) }.join
  # Generate 9th digit
  check_digit = generate_sin_check_digit("#{registry}#{partial}0").to_s
  registry + partial + check_digit
end

def sum(values)
  values.chars.each_with_index.inject(0) do |sum, (value, index)|
    sum + yield(value, index)
  end
end