Features/exceptions pipeline integration (#308)

web/backend/Shared/Shared.Application/Behaviors/UnhandledExceptionLoggingBehavior.cs

@@ -0,0 +1,86 @@
+using System.Text.Json;
+using System.Text.Json.Serialization.Metadata;
+using FluentValidation;
+using MediatR;
+using Microsoft.Extensions.Logging;
+
+namespace Shared.Application.Behaviors;
+
+/// <summary>
+///     MediatR pipeline behavior that logs unhandled exceptions together with the request type and
+///     payload, then rethrows them unchanged for <c>GlobalExceptionFilter</c> to map to a status code.
+/// </summary>
+public class UnhandledExceptionLoggingBehavior<TRequest, TResponse>(
+    ILogger<UnhandledExceptionLoggingBehavior<TRequest, TResponse>> logger
+) : IPipelineBehavior<TRequest, TResponse>
+    where TRequest : IRequest<TResponse>
+{
+    private static readonly string[] SensitiveFieldNames = ["password", "token"];
+
+    private static readonly JsonSerializerOptions SerializerOptions = new()
+    {
+        TypeInfoResolver = new DefaultJsonTypeInfoResolver
+        {
+            Modifiers = { RedactSensitiveProperties },
+        },
+    };
+
+    /// <inheritdoc/>
+    public async Task<TResponse> Handle(
+        TRequest request,
+        RequestHandlerDelegate<TResponse> next,
+        CancellationToken cancellationToken
+    )
+    {
+        try
+        {
+            return await next();
+        }
+        catch (ValidationException)
+        {
+            // Expected: ValidationBehavior already reports these as request errors, not incidents.
+            throw;
+        }
+        catch (Exception ex)
+        {
+            logger.LogError(
+                ex,
+                "Unhandled exception while processing {RequestName}: {RequestPayload}",
+                typeof(TRequest).Name,
+                Serialize(request)
+            );
+            throw;
+        }
+    }
+
+    private static string Serialize(TRequest request)
+    {
+        try
+        {
+            return JsonSerializer.Serialize(request, SerializerOptions);
+        }
+        catch (Exception)
+        {
+            return "<unable to serialize request payload>";
+        }
+    }
+
+    private static void RedactSensitiveProperties(JsonTypeInfo typeInfo)
+    {
+        if (typeInfo.Kind != JsonTypeInfoKind.Object)
+            return;
+
+        foreach (JsonPropertyInfo property in typeInfo.Properties)
+        {
+            if (property.PropertyType != typeof(string))
+                continue;
+
+            if (
+                SensitiveFieldNames.Any(name =>
+                    property.Name.Contains(name, StringComparison.OrdinalIgnoreCase)
+                )
+            )
+                property.Get = static _ => "***REDACTED***";
+        }
+    }
+}