DocumentService/DocumentOperator.Application/Common/Behaviors/LoggingBehavior.cs

using MediatR;
using Microsoft.Extensions.Logging;
using System.Diagnostics;

namespace DocumentOperator.Application.Common.Behaviors;

/// <summary>
/// MediatR Pipeline Behavior that logs requests and tracks performance
/// Executes AFTER ValidationBehavior, BEFORE Handler
/// </summary>
public class LoggingBehavior<TRequest, TResponse> : IPipelineBehavior<TRequest, TResponse>
    where TRequest : IRequest<TResponse>
{
    private readonly ILogger<LoggingBehavior<TRequest, TResponse>> _logger;

    public LoggingBehavior(ILogger<LoggingBehavior<TRequest, TResponse>> logger)
    {
        _logger = logger;
    }

    public async Task<TResponse> Handle(
        TRequest request,
        RequestHandlerDelegate<TResponse> next,
        CancellationToken cancellationToken)
    {
        var requestName = typeof(TRequest).Name;

        // Request Start
        _logger.LogInformation("Handling {RequestName}: {@Request}", requestName, request);

        // Performance Tracking
        var stopwatch = Stopwatch.StartNew();

        try
        {
            // Handler ausführen
            var response = await next();

            stopwatch.Stop();

            // Request Success
            _logger.LogInformation(
                "Handled {RequestName} in {ElapsedMs}ms",
                requestName,
                stopwatch.ElapsedMilliseconds
            );

            return response;
        }
        catch (Exception ex)
        {
            stopwatch.Stop();

            // Request Failed
            _logger.LogError(
                ex,
                "Error handling {RequestName} after {ElapsedMs}ms: {ErrorMessage}",
                requestName,
                stopwatch.ElapsedMilliseconds,
                ex.Message
            );

            throw; // Exception weiterwerfen (wird von Exception Middleware gefangen)
        }
    }
}