From 802c576c60d1cf728522788439a152cbc6a4ab5d Mon Sep 17 00:00:00 2001
From: Pascal Burri <pascal.burri@gmail.com>
Date: Sat, 26 Oct 2024 15:49:24 +0200
Subject: [PATCH] Updated luhn checksum to to work with base 2-36

---
 src/core/operations/LuhnChecksum.mjs | 53 +++++++++++++++++++---------
 1 file changed, 36 insertions(+), 17 deletions(-)

diff --git a/src/core/operations/LuhnChecksum.mjs b/src/core/operations/LuhnChecksum.mjs
index cb3a7c24..8bf3465f 100644
--- a/src/core/operations/LuhnChecksum.mjs
+++ b/src/core/operations/LuhnChecksum.mjs
@@ -1,5 +1,6 @@
 /**
- * @author n1073645 [n1073645@gmail.com]
+ * @author n1073645 [n1073645@gmail.com] 
+ * @author k3ach [k3ach@proton.me]
  * @copyright Crown Copyright 2020
  * @license Apache-2.0
  */
@@ -20,11 +21,17 @@ class LuhnChecksum extends Operation {
 
         this.name = "Luhn Checksum";
         this.module = "Default";
-        this.description = "The Luhn algorithm, also known as the modulus 10 or mod 10 algorithm, is a simple checksum formula used to validate a variety of identification numbers, such as credit card numbers, IMEI numbers and Canadian Social Insurance Numbers.";
-        this.infoURL = "https://wikipedia.org/wiki/Luhn_algorithm";
+        this.description = "The Luhn mod N algorithm is an extension to the Luhn algorithm (also known as mod 10 algorithm) that allows it to work with sequences of values in any even-numbered base. This can be useful when a check digit is required to validate an identification string composed of letters, a combination of letters and digits or any arbitrary set of N characters where N is divisible by 2.";
+        this.infoURL = "https://en.wikipedia.org/wiki/Luhn_mod_N_algorithm";
         this.inputType = "string";
         this.outputType = "string";
-        this.args = [];
+        this.args = [
+            {
+                "name": "Radix",
+                "type": "number",
+                "value": 10
+            }
+        ];
     }
 
     /**
@@ -33,26 +40,27 @@ class LuhnChecksum extends Operation {
      * @param {string} inputStr
      * @returns {number}
      */
-    checksum(inputStr) {
+    checksum(inputStr, radix = 10) {
         let even = false;
         return inputStr.split("").reverse().reduce((acc, elem) => {
-            // Convert element to integer.
-            let temp = parseInt(elem, 10);
+            // Convert element to an integer based on the provided radix.
+            let temp = parseInt(elem, radix);
 
-            // If element is not an integer.
-            if (isNaN(temp))
-                throw new OperationError("Character: " + elem + " is not a digit.");
+            // If element is not a valid number in the given radix.
+            if (isNaN(temp)) {
+                throw new Error("Character: " + elem + " is not valid in radix " + radix + ".");
+            }
 
             // If element is in an even position
             if (even) {
-                // Double the element and add the quotient and remainder together.
-                temp = 2 * elem;
-                temp = Math.floor(temp/10) + (temp % 10);
+                // Double the element and sum the quotient and remainder.
+                temp = 2 * temp;
+                temp = Math.floor(temp / radix) + (temp % radix);
             }
 
             even = !even;
             return acc + temp;
-        }, 0)  % 10;
+        }, 0) % radix; // Use radix as the modulus base
     }
 
     /**
@@ -63,9 +71,20 @@ class LuhnChecksum extends Operation {
     run(input, args) {
         if (!input) return "";
 
-        const checkSum = this.checksum(input);
-        let checkDigit = this.checksum(input + "0");
-        checkDigit = checkDigit === 0 ? 0 : (10-checkDigit);
+        let radix = args[0];
+
+        if (radix < 2 || radix > 36) {
+            throw new OperationError("Error: Radix argument must be between 2 and 36");
+        }
+
+        if (radix % 2 != 0) {
+            throw new OperationError("Error: Radix argument must be divisible by 2");
+        }
+
+        const checkSum = this.checksum(input, radix).toString(radix);
+        let checkDigit = this.checksum(input + "0", radix);
+        checkDigit = checkDigit === 0 ? 0 : (radix - checkDigit);
+        checkDigit = checkDigit.toString(radix)
 
         return `Checksum: ${checkSum}
 Checkdigit: ${checkDigit}