feat: DTOSS-9160 - NHS Num validator

src/ServiceLayer.Mesh/FileTypes/NbssAppointmentEvents/Validation/NhsNumValidator.cs

@@ -0,0 +1,38 @@
+using System.Text.RegularExpressions;
+
+namespace ServiceLayer.Mesh.FileTypes.NbssAppointmentEvents.Validation;
+
+public partial class NhsNumValidator() :
+    RegexValidator("NHS Num", NhsNumberRegex(), ErrorCodes.MissingNhsNum, ErrorCodes.InvalidNhsNum)
+{
+    protected override IEnumerable<ValidationError> RunAdditionalChecks(int rowNumber, string value)
+    {
+        if (!HasValidCheckDigit(value))
+        {
+            yield return new ValidationError
+            {
+                RowNumber = rowNumber,
+                Field = FieldName,
+                Error = "NHS Num has invalid check digit",
+                Code = ErrorCodes.InvalidNhsNumCheckDigit
+            };
+        }
+    }
+
+    private static bool HasValidCheckDigit(string value)
+    {
+        var weightedSum = 0;
+        for (var i = 0; i < 9; i++)
+        {
+            weightedSum += (10 - i) * (value[i] - '0');
+        }
+
+        var remainder = weightedSum % 11;
+        var expectedCheckDigit = (11 - remainder) % 11;
+
+        return expectedCheckDigit == value[9] - '0';
+    }
+
+    [GeneratedRegex(@"^\d{10}$", RegexOptions.Compiled)]
+    private static partial Regex NhsNumberRegex();
+}

src/ServiceLayer.Mesh/FileTypes/NbssAppointmentEvents/Validation/RegexValidator.cs

@@ -10,17 +10,19 @@ public class RegexValidator(
     string errorCodeInvalidFormat)
     : IRecordValidator
 {
+    protected string FieldName { get; } = fieldName;
+
     public IEnumerable<ValidationError> Validate(FileDataRecord fileDataRecord)
     {
-        var value = fileDataRecord[fieldName];
+        var value = fileDataRecord[FieldName];
 
         if (value == null)
         {
             yield return new ValidationError
             {
                 RowNumber = fileDataRecord.RowNumber,
-                Field = fieldName,
-                Error = $"{fieldName} is missing",
+                Field = FieldName,
+                Error = $"{FieldName} is missing",
                 Code = errorCodeMissing,
             };
             yield break;
@@ -31,10 +33,21 @@ public IEnumerable<ValidationError> Validate(FileDataRecord fileDataRecord)
             yield return new ValidationError
             {
                 RowNumber = fileDataRecord.RowNumber,
-                Field = fieldName,
-                Error = $"{fieldName} is in an invalid format",
+                Field = FieldName,
+                Error = $"{FieldName} is in an invalid format",
                 Code = errorCodeInvalidFormat,
             };
+            yield break;
+        }
+
+        foreach (var additionalError in RunAdditionalChecks(fileDataRecord.RowNumber, value))
+        {
+            yield return additionalError;
         }
     }
+
+    protected virtual IEnumerable<ValidationError> RunAdditionalChecks(int rowNumber, string value)
+    {
+        yield break;
+    }
 }

src/ServiceLayer.Mesh/FileTypes/NbssAppointmentEvents/Validation/ValidatorRegistry.cs

@@ -24,6 +24,7 @@ public static IEnumerable<IRecordValidator> GetAllRecordValidators()
                 ErrorCodes.InvalidAttendedNotScr),
             new MaxLengthValidator("Appointment ID", 27, ErrorCodes.MissingAppointmentId,
                 ErrorCodes.InvalidAppointmentId),
+            new NhsNumValidator(),
             new RegexValidator("Episode Type", EpisodeTypeRegex(), ErrorCodes.MissingEpisodeType,
                 ErrorCodes.InvalidEpisodeType),
             new MaxLengthValidator("Batch ID", 9, ErrorCodes.MissingBatchId,

tests/ServiceLayer.Mesh.Tests/FileTypes/NbssAppointmentEvents/Validation/NhsNumValidatorTests.cs

@@ -0,0 +1,82 @@
+using ServiceLayer.Mesh.FileTypes.NbssAppointmentEvents.Validation;
+
+namespace ServiceLayer.Mesh.Tests.FileTypes.NbssAppointmentEvents.Validation;
+
+public class NhsNumValidatorTests : ValidationTestBase
+{
+    [Fact]
+    public void Validate_NhsNumMissing_ReturnsValidationError()
+    {
+        // Arrange
+        var file = ParsedFileWithModifiedRecord(r => r.Fields.Remove("NHS Num"));
+
+        // Act
+        var validationErrors = Validate(file);
+
+        // Assert
+        validationErrors.ShouldContainValidationError(
+            "NHS Num",
+            "NHS Num is missing",
+            ErrorCodes.MissingNhsNum
+        );
+    }
+
+    [Theory]
+    [InlineData("308 407 5425")]       // we don't anticipate spaces
+    [InlineData("857320211")]          // too few character
+    [InlineData("90238807571")]        // Too many characters
+    [InlineData("159278895S")]         // invalid characters
+    public void Validate_NhsNumInvalidFormat_ReturnsValidationError(string value)
+    {
+        // Arrange
+        var file = ParsedFileWithModifiedRecord(r => r.Fields["NHS Num"] = value);
+
+        // Act
+        var validationErrors = Validate(file).ToList();
+
+        // Assert
+        validationErrors.ShouldContainValidationError(
+            "NHS Num",
+            "NHS Num is in an invalid format",
+            ErrorCodes.InvalidNhsNum
+        );
+    }
+
+    [Theory]
+    [InlineData("3244700471")]
+    [InlineData("7326012282")]
+    [InlineData("6245827145")]
+    [InlineData("4745895257")]
+    public void Validate_NhsNumInvalidCheckDigit_ReturnsValidationError(string value)
+    {
+        // Arrange
+        var file = ParsedFileWithModifiedRecord(r => r.Fields["NHS Num"] = value);
+
+        // Act
+        var validationErrors = Validate(file).ToList();
+
+        // Assert
+        validationErrors.ShouldContainValidationError(
+            "NHS Num",
+            "NHS Num has invalid check digit",
+            ErrorCodes.InvalidNhsNumCheckDigit
+        );
+    }
+
+    [Theory]
+    [InlineData("4941273230")]
+    [InlineData("6451357219")]
+    [InlineData("3365582983")]
+    [InlineData("8799244780")]
+    public void Validate_NHSNumValidFormat_NoValidationErrorsReturned(string value)
+    {
+        // Arrange
+        var file = ParsedFileWithModifiedRecord(r => r.Fields["NHS Num"] = value);
+
+        // Act
+        var validationErrors = Validate(file).ToList();
+
+        // Assert
+        Assert.Empty(validationErrors);
+    }
+}