Enhance input validation for MyNumber verification and check digit endpoints

Author: hsaito

MyNumberNET/MyNumber.cs

@@ -40,13 +40,11 @@ public static int CalculateCheckDigits(int[] number)
                 throw new MyNumberMalformedException("Malformed sequence. Must be 11 digits.");
             if (Array.Exists(number, n => n < 0 || n > 9))
                 throw new MyNumberMalformedException("All digits must be between 0 and 9.");
-            Array.Reverse(number);
             var sum = 0;
             for (var n = 1; n < 7; n++)
-                sum += (n + 1) * number[n - 1];
+                sum += (n + 1) * number[11 - n];
             for (var n = 7; n < 12; n++)
-                sum += (n - 5) * number[n - 1];
-            Array.Reverse(number);
+                sum += (n - 5) * number[11 - n];
             if (sum % 11 <= 1)
                 return 0;
             return 11 - sum % 11;

MyNumberNET_ApiServer/Controllers/MyNumberController.cs

@@ -18,6 +18,13 @@ public class MyNumberController : ControllerBase
         [HttpPost("verify")]
         public ActionResult<bool> Verify([FromBody] int[] number)
         {
+            // Input validation before calling business logic
+            if (number == null)
+                return BadRequest("Input array is null.");
+            if (number.Length != 12)
+                return BadRequest("Malformed sequence. Must be 12 digits.");
+            if (number.Any(n => n < 0 || n > 9))
+                return BadRequest("All digits must be between 0 and 9.");
             try
             {
                 bool isValid = MyNumber.VerifyNumber(number);
@@ -37,6 +44,13 @@ public ActionResult<bool> Verify([FromBody] int[] number)
         [HttpPost("checkdigit")]
         public ActionResult<int> CheckDigit([FromBody] int[] number)
         {
+            // Input validation before calling business logic
+            if (number == null)
+                return BadRequest("Input array is null.");
+            if (number.Length != 11)
+                return BadRequest("Malformed sequence. Must be 11 digits.");
+            if (number.Any(n => n < 0 || n > 9))
+                return BadRequest("All digits must be between 0 and 9.");
             try
             {
                 int checkDigit = MyNumber.CalculateCheckDigits(number);