fix(templates): hoist (DataType,ElementDataType,Value) attribute validation into TemplateService (#92)

src/ZB.MOM.WW.ScadaBridge.TemplateEngine/TemplateService.cs

@@ -2,6 +2,7 @@ using ZB.MOM.WW.ScadaBridge.Commons.Entities.Templates;
 using ZB.MOM.WW.ScadaBridge.Commons.Interfaces.Repositories;
 using ZB.MOM.WW.ScadaBridge.Commons.Interfaces.Services;
 using ZB.MOM.WW.ScadaBridge.Commons.Types;
+using ZB.MOM.WW.ScadaBridge.Commons.Types.Enums;
 
 namespace ZB.MOM.WW.ScadaBridge.TemplateEngine;
 
@@ -266,6 +267,16 @@ public class TemplateService
         string user,
         CancellationToken cancellationToken = default)
     {
+        // Defense-in-depth (#92): hoist the (DataType, ElementDataType, Value)
+        // guard — previously only enforced on the CLI/API path in
+        // ManagementActor.ValidateAttributeTypes — into the service so the
+        // Central UI's direct TemplateService write path shares one server-side
+        // check. Mirrors ValidateAttributeTypes exactly, reusing AttributeValueCodec.
+        var typeError = ValidateAttributeTypes(
+            attribute.Name, attribute.DataType, attribute.ElementDataType, attribute.Value);
+        if (typeError != null)
+            return Result<TemplateAttribute>.Failure(typeError);
+
         var template = await _repository.GetTemplateByIdAsync(templateId, cancellationToken);
         if (template == null)
             return Result<TemplateAttribute>.Failure($"Template with ID {templateId} not found.");
@@ -312,6 +323,17 @@ public class TemplateService
         if (existing == null)
             return Result<TemplateAttribute>.Failure($"Attribute with ID {attributeId} not found.");
 
+        // Defense-in-depth (#92): hoist the (DataType, ElementDataType, Value)
+        // guard out of ManagementActor.ValidateAttributeTypes so the Central UI's
+        // direct TemplateService write path shares one server-side check. DataType
+        // and ElementDataType are fixed by the defining level (not copied from the
+        // proposed attribute below), so the effective persisted triple is the
+        // existing type pairing with the proposed value. Reuses AttributeValueCodec.
+        var typeError = ValidateAttributeTypes(
+            existing.Name, existing.DataType, existing.ElementDataType, proposed.Value);
+        if (typeError != null)
+            return Result<TemplateAttribute>.Failure(typeError);
+
         // Validate override rules if this is an override (parent has same-named attribute)
         var template = await _repository.GetTemplateByIdAsync(existing.TemplateId, cancellationToken);
         if (template?.ParentTemplateId != null)
@@ -412,6 +434,52 @@ public class TemplateService
         return Result<bool>.Success(true);
     }
 
+    /// <summary>
+    /// Validates the (DataType, ElementDataType, Value) triple for an attribute.
+    /// Returns a human-readable failure message (for <c>Result.Failure</c>), or
+    /// <c>null</c> when the triple is valid. Mirrors the CLI/API-path guard in
+    /// <c>ManagementActor.ValidateAttributeTypes</c> so both server write paths
+    /// share one server-side check (#92), reusing <see cref="AttributeValueCodec"/>
+    /// for the element-type and value-decode logic:
+    /// <list type="bullet">
+    /// <item>DataType must be a defined enum value.</item>
+    /// <item>List attributes require a valid scalar element type, and a present
+    /// default value must decode against it.</item>
+    /// <item>Scalar attributes may not carry an element type.</item>
+    /// </list>
+    /// </summary>
+    private static string? ValidateAttributeTypes(
+        string name, DataType dataType, DataType? elementType, string? value)
+    {
+        if (!Enum.IsDefined(dataType))
+            return $"Attribute '{name}' has an unrecognised data type.";
+
+        if (dataType == DataType.List)
+        {
+            if (elementType is null || !AttributeValueCodec.IsValidElementType(elementType.Value))
+                return $"List attribute '{name}' requires a valid element type " +
+                       "(String, Int32, Float, Double, Boolean, DateTime).";
+
+            if (!string.IsNullOrWhiteSpace(value))
+            {
+                try
+                {
+                    AttributeValueCodec.Decode(value, DataType.List, elementType);
+                }
+                catch (FormatException ex)
+                {
+                    return $"List attribute '{name}' has an invalid list value: {ex.Message}";
+                }
+            }
+        }
+        else if (elementType is not null)
+        {
+            return $"Attribute '{name}': ElementDataType is only valid on List attributes.";
+        }
+
+        return null;
+    }
+
     // ========================================================================
     // WP-3: Alarm Definitions
     // ========================================================================