davidoram · February 26, 2024 22:15 · Feb 26, 2024
diff --git a/convert-card-number-to-barcode.rb b/convert-card-number-to-barcode.rb
@@ -0,0 +1,83 @@
+#!/usr/bin/env ruby
+# Convert a FlyBuys card number to a barcode
+
+def get_check_sum_from_thirteen_digit_code(card_number)
+  evens = 0
+  odds = 0
+
+  # Loop over all characters
+  card_number.chars.each_with_index do |character, index|
+    # Don't include the last character - 1
+    break if index == card_number.length - 1
+
+    # Convert to a number
+    num = character.to_i
+
+    if index.odd?
+      evens += num
+    else
+      odds += num
+    end
+  end
+
+  (10 - (((evens * 3) + odds) % 10)) % 10
+end
+
+def is_card_number_valid(card_number)
+  # Implement your validation logic here
+  true
+end
+
+def is_barcode_valid(barcode)
+  return false unless barcode[0..2] == "264"
+  return false unless barcode.length == 13
+  return false unless barcode.chars.all? { |char| char =~ /[0-9]/ }
+  return false unless is_checksum_valid(barcode)
+
+  true
+end
+
+def is_checksum_valid(barcode)
+  number_one = 0
+  number_two = 0
+
+  # Create number one
+  (11).step(0, -2) do |i|
+    char = barcode[i]
+    val = char.to_i
+    number_one += val
+  end
+  number_one *= 3
+
+  # Create number two
+  (0).step(12, 2) do |i|
+    char = barcode[i]
+    val = char.to_i
+    number_two += val
+  end
+  number_two += number_one
+
+  # Calculate the check digit
+  check_digit = (10 - (number_two % 10)) % 10
+
+  # Validate
+  last_digit = barcode[12].to_i
+  check_digit == last_digit
+end
+
+def convert_card_number_to_barcode(card_number)
+  raise "Cannot convert an invalid card number to a barcode" unless is_card_number_valid(card_number)
+
+  barcode = card_number[0..5].gsub(card_number[0..5], "264") + card_number[6..-1]
+  check_sum = get_check_sum_from_thirteen_digit_code(barcode)
+
+  # Update the last number with the checksum
+  barcode = barcode[0..-2] + check_sum.to_s
+
+  # Post condition validation
+  raise "An invalid barcode was created from a card number" unless is_barcode_valid(barcode)
+
+  barcode
+end
+
+puts convert_card_number_to_barcode(ARGV[0])