refactor: DTOSS-9159 - split file-level validation into four separate classes

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

@@ -0,0 +1,25 @@
+using System.Text.RegularExpressions;
+using ServiceLayer.Mesh.FileTypes.NbssAppointmentEvents.Models;
+
+namespace ServiceLayer.Mesh.FileTypes.NbssAppointmentEvents.Validation;
+
+public partial class ExtractIdValidator() :
+    HeaderFieldRegexValidator(h => h.ExtractId, "Extract ID", ExtractIdRegex(), ErrorCodes.MissingExtractId, ErrorCodes.InvalidExtractId)
+{
+    [GeneratedRegex(@"^\d{8}$")]
+    private static partial Regex ExtractIdRegex();
+
+    protected override IEnumerable<ValidationError> RunAdditionalChecks(ParsedFile file, string value, bool hasErrored)
+    {
+        if (file.FileTrailer != null && file.FileHeader!.ExtractId != file.FileTrailer.ExtractId)
+        {
+            yield return new ValidationError
+            {
+                Field = "Extract ID",
+                Code = ErrorCodes.InconsistentExtractId,
+                Error = "Extract ID does not match value in header",
+                Scope = ValidationErrorScope.Trailer
+            };
+        }
+    }
+}

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

@@ -14,6 +14,12 @@ public class HeaderFieldRegexValidator(
 {
     public IEnumerable<ValidationError> Validate(ParsedFile file)
     {
+        if (file.FileHeader == null)
+        {
+            yield break;
+        }
+
+        var hasErrored = false;
         var header = file.FileHeader!;
         var value = fieldSelector.Compile().Invoke(header);
 
@@ -31,6 +37,7 @@ public IEnumerable<ValidationError> Validate(ParsedFile file)
 
         if (!pattern.IsMatch(value))
         {
+            hasErrored = true;
             yield return new ValidationError
             {
                 Scope = ValidationErrorScope.Header,
@@ -39,5 +46,15 @@ public IEnumerable<ValidationError> Validate(ParsedFile file)
                 Code = errorCodeInvalidFormat,
             };
         }
+
+        foreach (var additionalError in RunAdditionalChecks(file, value, hasErrored))
+        {
+            yield return additionalError;
+        }
+    }
+
+    protected virtual IEnumerable<ValidationError> RunAdditionalChecks(ParsedFile file, string value, bool hasErrored)
+    {
+        yield break;
     }
 }

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

@@ -0,0 +1,19 @@
+using ServiceLayer.Mesh.FileTypes.NbssAppointmentEvents.Models;
+
+namespace ServiceLayer.Mesh.FileTypes.NbssAppointmentEvents.Validation;
+
+public class HeaderPresenceValidator : IFileValidator
+{
+    public IEnumerable<ValidationError> Validate(ParsedFile file)
+    {
+        if (file.FileHeader == null)
+        {
+            yield return new ValidationError
+            {
+                Code = ErrorCodes.MissingHeader,
+                Error = "Header is missing",
+                Scope = ValidationErrorScope.File
+            };
+        }
+    }
+}

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

@@ -0,0 +1,34 @@
+using System.Text.RegularExpressions;
+using ServiceLayer.Mesh.FileTypes.NbssAppointmentEvents.Models;
+
+namespace ServiceLayer.Mesh.FileTypes.NbssAppointmentEvents.Validation;
+
+public partial class RecordCountValidator() :
+    HeaderFieldRegexValidator(h => h.RecordCount, "Record count", RecordCountRegex(), ErrorCodes.MissingRecordCount, ErrorCodes.InvalidRecordCount)
+{
+    [GeneratedRegex(@"^(?!000000)\d{6}$")]
+    private static partial Regex RecordCountRegex();
+
+    protected override IEnumerable<ValidationError> RunAdditionalChecks(ParsedFile file, string value, bool hasErrored)
+    {
+        if (file.FileTrailer != null && file.FileHeader!.RecordCount != file.FileTrailer.RecordCount)
+        {
+            yield return new ValidationError
+            {
+                Field = "Record count",
+                Code = ErrorCodes.InconsistentRecordCount,
+                Error = "Record count does not match value in header",
+                Scope = ValidationErrorScope.Trailer
+            };
+        }
+        else if (!hasErrored && file.DataRecords.Count != int.Parse(file.FileHeader!.RecordCount!))
+        {
+            yield return new ValidationError
+            {
+                Code = ErrorCodes.UnexpectedRecordCount,
+                Error = "Record count does not match value in header and trailer",
+                Scope = ValidationErrorScope.File
+            };
+        }
+    }
+}

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

@@ -0,0 +1,19 @@
+using ServiceLayer.Mesh.FileTypes.NbssAppointmentEvents.Models;
+
+namespace ServiceLayer.Mesh.FileTypes.NbssAppointmentEvents.Validation;
+
+public class TrailerPresenceValidator : IFileValidator
+{
+    public IEnumerable<ValidationError> Validate(ParsedFile file)
+    {
+        if (file.FileTrailer == null)
+        {
+            yield return new ValidationError
+            {
+                Code = ErrorCodes.MissingTrailer,
+                Error = "Trailer is missing",
+                Scope = ValidationErrorScope.File
+            };
+        }
+    }
+}

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

@@ -68,7 +68,12 @@ public static IEnumerable<IRecordValidator> GetAllRecordValidators()
 
     public static IEnumerable<IFileValidator> GetAllFileValidators()
     {
-        return [new FileValidator()];
+        return [
+            new HeaderPresenceValidator(),
+            new TrailerPresenceValidator(),
+            new ExtractIdValidator(),
+            new RecordCountValidator()
+        ];
     }
 
     [GeneratedRegex(@"^[BCU]$", RegexOptions.Compiled)]

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

@@ -0,0 +1,88 @@
+using ServiceLayer.Mesh.FileTypes.NbssAppointmentEvents.Validation;
+
+namespace ServiceLayer.Mesh.Tests.FileTypes.NbssAppointmentEvents.Validation;
+
+public class ExtractIdValidatorTests : ValidationTestBase
+{
+    [Fact]
+    public void Validate_HeaderExtractIdMissing_ReturnsValidationError()
+    {
+        // Arrange
+        var file = ValidParsedFile;
+        file.FileHeader!.ExtractId = null;
+
+        // Act
+        var validationErrors = Validate(file);
+
+        // Assert
+        validationErrors.ShouldContainValidationError(
+            "Extract ID",
+            "Extract ID is missing",
+            ErrorCodes.MissingExtractId,
+            ValidationErrorScope.Header
+        );
+    }
+
+    [Theory]
+    [InlineData("1")]         // Missing leading zeroes
+    [InlineData("100000000")] // Too large
+    [InlineData("")]          // Blank
+    [InlineData("asdf")]      // NaN
+    public void Validate_HeaderExtractIdInvalidFormat_ReturnsValidationError(string value)
+    {
+        // Arrange
+        var file = ValidParsedFile;
+        file.FileHeader!.ExtractId = value;
+
+        // Act
+        var validationErrors = Validate(file).ToList();
+
+        // Assert
+        validationErrors.ShouldContainValidationError(
+            "Extract ID",
+            "Extract ID is in an invalid format",
+            ErrorCodes.InvalidExtractId,
+            ValidationErrorScope.Header
+        );
+    }
+
+    [Theory]
+    [InlineData("00000000")]
+    [InlineData("00000001")]
+    [InlineData("99999999")]
+    public void Validate_HeaderExtractIdValidFormat_NoValidationErrorsReturned(string value)
+    {
+        // Arrange
+        var file = ValidParsedFile;
+        file.FileHeader!.ExtractId = value;
+        file.FileTrailer!.ExtractId = value;
+
+        // Act
+        var validationErrors = Validate(file).ToList();
+
+        // Assert
+        Assert.Empty(validationErrors);
+    }
+
+    [Theory]
+    [InlineData(null)]
+    [InlineData("")]
+    [InlineData("00000108")]
+    public void Validate_TrailerExtractIdMismatch_ReturnsValidationError(string? value)
+    {
+        // Arrange
+        var file = ValidParsedFile;
+        file.FileTrailer!.ExtractId = value;
+
+        // Act
+        var validationErrors = Validate(file).ToList();
+
+        // Assert
+        validationErrors.ShouldContainValidationError(
+            "Extract ID",
+            "Extract ID does not match value in header",
+            ErrorCodes.InconsistentExtractId,
+            ValidationErrorScope.Trailer
+        );
+    }
+}