The Ideal Logging System

using System;
using System.Collections.Generic;

namespace LoggingSystem
{
    public enum NotificationLevel
    {
        Noise,
        Warning,
        Exception
    }

    public class Notification
    {
        public DateTime TimeStamp { get; set; }

        public NotificationLevel Level { get; set; }

        public string Message { get; set; }

        public string StackTrace { get; set; }

        public Notification(Exception err)
        {
            TimeStamp = DateTime.Now;

            StackTrace = err.StackTrace;

            Level = NotificationLevel.Exception;

            Message = err.Message;
        }

        public Notification(NotificationLevel level, string message)
        {
            TimeStamp = DateTime.Now;

#if DEBUG
            StackTrace = new System.Diagnostics.StackTrace().ToString();
#endif

            Level = level;

            Message = message;
        }

        public override string ToString()
        {
            return string.Format("{0}: {1}", Level, Message);
        }
    }

    public interface INotificationSubscriber
    {
        void ReceiveNotification(Notification notification);
    }

    public class LoggingService
    {
        public LoggingService()
        {
            _notifications = new List<Notification>();

            _subscribers = new List<INotificationSubscriber>();
        }

        public void Notify(Exception err)
        {
            _notifications.Add(new Notification(err));
        }

        public void Notify(NotificationLevel level, string format, params object[] args)
        {
            _notifications.Add(new Notification(level, string.Format(format, args)));
        }

        public void Notify(string format, params object[] args)
        {
            _notifications.Add(new Notification(NotificationLevel.Noise, string.Format(format, args)));
        }

        public void Subscribe(INotificationSubscriber subscriber)
        {
            _subscribers.Add(subscriber);
        }

        public void Unsubscribe(INotificationSubscriber subscriber)
        {
            _subscribers.Remove(subscriber);
        }

        protected void NotifySubscribers(Notification notification)
        {
            foreach (var subscriber in _subscribers)
            {
                subscriber.ReceiveNotification(notification);
            }
        }

        private readonly List<INotificationSubscriber> _subscribers;

        private readonly List<Notification> _notifications;
    }
}