namespace Ds.Module.MediatR
{
    /// <summary>
    /// 
    /// </summary>
    /// <typeparam name="TRequest"></typeparam>
    /// <typeparam name="TResponse"></typeparam>
    public class PerformanceMonitorBehavior<TRequest, TResponse> : IPipelineBehavior<TRequest, TResponse>
    {
        private ILogger<PerformanceMonitorBehavior<TRequest, TResponse>> _logger;

        public PerformanceMonitorBehavior(ILogger<PerformanceMonitorBehavior<TRequest, TResponse>> logger)
        {
            _logger = logger ?? throw new ArgumentNullException(nameof(logger));
        }

        public async Task<TResponse> Handle(TRequest request, RequestHandlerDelegate<TResponse> next, CancellationToken cancellationToken)
        {
            // 只有在调试模式下才记录，这样就不会在生产环境中加重负担
#if DEBUG
            var typeName = typeof(TRequest).Name;

            LogPrePerformanceData(typeName);

            Stopwatch stopwatch = Stopwatch.StartNew();
            try
            {
                return await next();
            }
            finally
            {
                stopwatch.Stop();
                LogPostPerformanceData(typeName, stopwatch);
            }
#else
        return await next();
#endif
        }

        private void LogPrePerformanceData(string typeName)
        {
            _logger.LogInformation("----- Handling command {CommandType}", typeName);
        }

        private void LogPostPerformanceData(string typeName, Stopwatch stopwatch)
        {
            _logger.LogInformation("----- Done handling command {CommandType} (ElapsedMilliseconds = {ElapsedMilliseconds})", typeName, stopwatch.ElapsedMilliseconds);
        }

        //使用时需要在Startup.cs中注册   
        //services.AddTransient(typeof(IPipelineBehavior<,>), typeof(ValidationBehavior<,>));
        //services.AddTransient(typeof(IPipelineBehavior<,>), typeof(PerformanceMonitorBehavior<,>));

    }
}