source: branches/eraser6/CodeReview/Eraser.Util/Logger.cs @ 1777

/* 
 * $Id$
 * Copyright 2008-2010 The Eraser Project
 * Original Author: Joel Low <lowjoel@users.sourceforge.net>
 * Modified By:
 * 
 * This file is part of Eraser.
 * 
 * Eraser is free software: you can redistribute it and/or modify it under the
 * terms of the GNU General Public License as published by the Free Software
 * Foundation, either version 3 of the License, or (at your option) any later
 * version.
 * 
 * Eraser is distributed in the hope that it will be useful, but WITHOUT ANY
 * WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
 * A PARTICULAR PURPOSE. See the GNU General Public License for more details.
 * 
 * A copy of the GNU General Public License can be found at
 * <http://www.gnu.org/licenses/>.
 */

using System;
using System.Linq;
using System.Collections.Generic;
using System.Text;

using System.Collections.ObjectModel;
using System.Threading;
using System.Runtime.Serialization;
using System.Security.Permissions;

namespace Eraser.Util
{
    /// <summary>
    /// The levels of logging allowing for the filtering of messages.
    /// </summary>
    public enum LogLevel
    {
        /// <summary>
        /// Informative messages.
        /// </summary>
        Information,

        /// <summary>
        /// Notice messages.
        /// </summary>
        Notice,

        /// <summary>
        /// Warning messages.
        /// </summary>
        Warning,

        /// <summary>
        /// Error messages.
        /// </summary>
        Error,

        /// <summary>
        /// Fatal errors.
        /// </summary>
        Fatal
    }

    /// <summary>
    /// Represents a log entry.
    /// </summary>
    [Serializable]
    public struct LogEntry : ISerializable
    {
        #region Serialization code
        private LogEntry(SerializationInfo info, StreamingContext context)
            : this()
        {
            Level = (LogLevel)info.GetValue("Level", typeof(LogLevel));
            Timestamp = (DateTime)info.GetValue("Timestamp", typeof(DateTime));
            Message = (string)info.GetValue("Message", typeof(string));
        }

        [SecurityPermission(SecurityAction.Demand, SerializationFormatter = true)]
        public void GetObjectData(SerializationInfo info, StreamingContext context)
        {
            info.AddValue("Level", Level);
            info.AddValue("Timestamp", Timestamp);
            info.AddValue("Message", Message);
        }
        #endregion

        /// <summary>
        /// Creates a LogEntry structure.
        /// </summary>
        /// <param name="message">The log message.</param>
        /// <param name="level">The type of log entry.</param>
        public LogEntry(string message, LogLevel level)
            : this()
        {
            Message = message;
            Level = level;
            Timestamp = DateTime.Now;
        }

        /// <summary>
        /// The type of log entry.
        /// </summary>
        public LogLevel Level { get; private set; }

        /// <summary>
        /// The time which the message was logged.
        /// </summary>
        public DateTime Timestamp { get; private set; }

        /// <summary>
        /// The log message.
        /// </summary>
        public string Message { get; private set; }
    }

    /// <summary>
    /// Event Data for all Logger events.
    /// </summary>
    public class LogEventArgs : EventArgs
    {
        /// <summary>
        /// Constructor.
        /// </summary>
        /// <param name="entry">The log entry that was just logged.</param>
        public LogEventArgs(LogEntry entry)
        {
            LogEntry = entry;
        }

        /// <summary>
        /// The log entry that was just logged.
        /// </summary>
        public LogEntry LogEntry { get; private set; }
    }

    /// <summary>
    /// Provides a standard logging interface to the rest of the Eraser classes.
    /// </summary>
    public static class Logger
    {
        static Logger()
        {
            Listeners = new LogThreadDictionary();
        }

        /// <summary>
        /// Logs an informational message.
        /// </summary>
        /// <param name="message">The message to log.</param>
        public static void Log(string message)
        {
            Log(new LogEntry(message, LogLevel.Information));
        }

        /// <summary>
        /// Logs a message to the logger.
        /// </summary>
        /// <param name="message">The message to store.</param>
        /// <param name="level">The level of the message.</param>
        public static void Log(string message, LogLevel level)
        {
            Log(new LogEntry(message, level));
        }

        /// <summary>
        /// Logs the provided entry to the logger.
        /// </summary>
        /// <param name="entry">The log entry to store.</param>
        public static void Log(LogEntry entry)
        {
            Thread currentThread = Thread.CurrentThread;
            List<ILogTarget> targets = new List<ILogTarget>();

            if (Listeners.ContainsKey(currentThread))
            {
                LogThreadTargets threadTargets = Listeners[currentThread];
                if (threadTargets != null)
                    targets.AddRange(threadTargets);
            }

            targets.ForEach(
                target => target.OnEventLogged(currentThread, new LogEventArgs(entry)));
        }

        /// <summary>
        /// The list of listeners for events on a particular thread.
        /// </summary>
        public static LogThreadDictionary Listeners { get; private set; }
    }

    /// <summary>
    /// The Logger Thread Dictionary, which maps log event listeners to threads.
    /// This mainly serves as a thread-safe Dictionary.
    /// </summary>
    public class LogThreadDictionary : IDictionary<Thread, LogThreadTargets>
    {
        #region IDictionary<Thread,LogThreadTargets> Members

        public void Add(Thread key, LogThreadTargets value)
        {
            lock (Dictionary)
                Dictionary.Add(key, value);
        }

        public bool ContainsKey(Thread key)
        {
            return Dictionary.ContainsKey(key);
        }

        public ICollection<Thread> Keys
        {
            get
            {
                lock (Dictionary)
                {
                    Thread[] result = new Thread[Dictionary.Keys.Count];
                    Dictionary.Keys.CopyTo(result, 0);

                    return new ReadOnlyCollection<Thread>(result);
                }
            }
        }

        public bool Remove(Thread key)
        {
            lock (Dictionary)
                return Dictionary.Remove(key);
        }

        public bool TryGetValue(Thread key, out LogThreadTargets value)
        {
            lock (Dictionary)
                return Dictionary.TryGetValue(key, out value);
        }

        public ICollection<LogThreadTargets> Values
        {
            get
            {
                lock (Dictionary)
                {
                    LogThreadTargets[] result =
                        new LogThreadTargets[Dictionary.Values.Count];
                    Dictionary.Values.CopyTo(result, 0);

                    return new ReadOnlyCollection<LogThreadTargets>(result);
                }
            }
        }

        public LogThreadTargets this[Thread key]
        {
            get
            {
                lock (Dictionary)
                    return Dictionary[key];
            }
            set
            {
                lock (Dictionary)
                    Dictionary[key] = value;
            }
        }

        #endregion

        #region ICollection<KeyValuePair<Thread,LogThreadTargets>> Members

        public void Add(KeyValuePair<Thread, LogThreadTargets> item)
        {
            lock (Dictionary)
                Dictionary.Add(item.Key, item.Value);
        }

        public void Clear()
        {
            lock (Dictionary)
                Dictionary.Clear();
        }

        public bool Contains(KeyValuePair<Thread, LogThreadTargets> item)
        {
            lock (Dictionary)
                return Dictionary.ContainsKey(item.Key) && Dictionary[item.Key] == item.Value;
        }

        public void CopyTo(KeyValuePair<Thread, LogThreadTargets>[] array, int arrayIndex)
        {
            throw new NotImplementedException();
        }

        public int Count
        {
            get
            {
                lock (Dictionary)
                    return Dictionary.Count;
            }
        }

        public bool IsReadOnly
        {
            get { return false; }
        }

        public bool Remove(KeyValuePair<Thread, LogThreadTargets> item)
        {
            lock (Dictionary)
                return Dictionary.Remove(item.Key);
        }

        #endregion

        #region IEnumerable<KeyValuePair<Thread,LogThreadTargets>> Members

        public IEnumerator<KeyValuePair<Thread, LogThreadTargets>> GetEnumerator()
        {
            return Dictionary.GetEnumerator();
        }

        #endregion

        #region IEnumerable Members

        System.Collections.IEnumerator System.Collections.IEnumerable.GetEnumerator()
        {
            return Dictionary.GetEnumerator();
        }

        #endregion

        /// <summary>
        /// The backing store for this dictionary.
        /// </summary>
        private Dictionary<Thread, LogThreadTargets> Dictionary =
            new Dictionary<Thread, LogThreadTargets>();
    }

    public class LogThreadTargets : IList<ILogTarget>
    {
        #region IList<ILogTarget> Members

        public int IndexOf(ILogTarget item)
        {
            lock (List)
                return List.IndexOf(item);
        }

        public void Insert(int index, ILogTarget item)
        {
            lock (List)
                List.Insert(index, item);
        }

        public void RemoveAt(int index)
        {
            lock (List)
                List.RemoveAt(index);
        }

        public ILogTarget this[int index]
        {
            get
            {
                lock (List)
                    return List[index];
            }
            set
            {
                lock (List)
                    List[index] = value;
            }
        }

        #endregion

        #region ICollection<ILogTarget> Members

        public void Add(ILogTarget item)
        {
            lock (List)
                List.Add(item);
        }

        public void Clear()
        {
            lock (List)
                List.Clear();
        }

        public bool Contains(ILogTarget item)
        {
            lock (List)
                return List.Contains(item);
        }

        public void CopyTo(ILogTarget[] array, int arrayIndex)
        {
            lock (List)
                List.CopyTo(array, arrayIndex);
        }

        public int Count
        {
            get
            {
                lock (List)
                    return List.Count;
            }
        }

        public bool IsReadOnly
        {
            get { return false; }
        }

        public bool Remove(ILogTarget item)
        {
            lock (List)
                return List.Remove(item);
        }

        #endregion

        #region IEnumerable<ILogTarget> Members

        public IEnumerator<ILogTarget> GetEnumerator()
        {
            return List.GetEnumerator();
        }

        #endregion

        #region IEnumerable Members

        System.Collections.IEnumerator System.Collections.IEnumerable.GetEnumerator()
        {
            return List.GetEnumerator();
        }

        #endregion

        /// <summary>
        /// The backing store for this list.
        /// </summary>
        private List<ILogTarget> List = new List<ILogTarget>();
    }

    /// <summary>
    /// The logger target interface which all interested listeners of log events must
    /// implement.
    /// </summary>
    public interface ILogTarget
    {
        /// <summary>
        /// The handler for events.
        /// </summary>
        /// <param name="sender">The sender of the event.</param>
        /// <param name="e">The event data associated with the event.</param>
        void OnEventLogged(object sender, LogEventArgs e);

        /// <summary>
        /// Chains the provided target to the current target, so that when this
        /// target receives an event, the provided target is also executed.
        /// </summary>
        /// <param name="target">The target to chain with the current one.</param>
        /// <remarks>Chaining a target multiple times will cause the target to
        /// be invoked multiple times for every event.</remarks>
        void Chain(ILogTarget target);

        /// <summary>
        /// Unchains the provided target from the current target, so that the
        /// provided target is no longer invoked when this target receives an event.
        /// </summary>
        /// <param name="target">The target to unchain</param>
        /// <remarks>Multiply-chained targets need to be unchained the same amount
        /// of time to be completely removed.</remarks>
        void Unchain(ILogTarget target);
    }

    /// <summary>
    /// Registers a provided log target to receive log messages for the lifespan
    /// of this object.
    /// </summary>
    public sealed class LogSession : IDisposable
    {
        /// <summary>
        /// Constructor. Registers the given log target with the provided threads
        /// for listening for log messages.
        /// </summary>
        /// <param name="target">The target that should receive events.</param>
        /// <param name="threads">The threads which the target will be registered
        /// with for event notifications.</param>
        public LogSession(ILogTarget target, params Thread[] threads)
        {
            Target = target;
            Threads = threads.Distinct().ToArray();

            foreach (Thread thread in Threads)
                Logger.Listeners[thread].Add(target);
        }

        /// <summary>
        /// Constructor. Registered the given log target with the current thread
        /// for listening for log messages.
        /// </summary>
        /// <param name="target">The target which should receive events</param>
        public LogSession(ILogTarget target)
            : this(target, Thread.CurrentThread)
        {
        }

        #region IDisposable Members

        ~LogSession()
        {
            Dispose(false);
        }

        private void Dispose(bool disposing)
        {
            if (Threads == null || Target == null)
                return;

            if (disposing)
            {
                //Disconnect the event handler from the threads.
                foreach (Thread thread in Threads)
                    Logger.Listeners[thread].Remove(Target);
            }

            Threads = null;
            Target = null;
        }

        public void Dispose()
        {
            Dispose(true);
            GC.SuppressFinalize(this);
        }

        #endregion

        /// <summary>
        /// The target that should receive events. If this is null, the object
        /// has been disposed.
        /// </summary>
        private ILogTarget Target;

        /// <summary>
        /// The list of threads which the target will be registered with for event
        /// notifications. If this is null, the object is disposd.
        /// </summary>
        private Thread[] Threads;
    }

    /// <summary>
    /// Collects a list of log entries into one session.
    /// </summary>
    /// <remarks>Instance functions of this class are thread-safe.</remarks>
    public class LogSink : ILogTarget, IList<LogEntry>
    {
        #region ILoggerTarget Members

        public void OnEventLogged(object sender, LogEventArgs e)
        {
            lock (List)
                List.Add(e.LogEntry);

            lock (ChainedTargets)
                ChainedTargets.ForEach(target => target.OnEventLogged(sender, e));
        }

        public void Chain(ILogTarget target)
        {
            lock (ChainedTargets)
                ChainedTargets.Add(target);
        }

        public void Unchain(ILogTarget target)
        {
            lock (ChainedTargets)
                ChainedTargets.Remove(target);
        }

        /// <summary>
        /// The list of targets which are chained to this one.
        /// </summary>
        private List<ILogTarget> ChainedTargets = new List<ILogTarget>();

        #endregion

        #region IList<LogEntry> Members

        public int IndexOf(LogEntry item)
        {
            lock (List)
                return IndexOf(item);
        }

        public void Insert(int index, LogEntry item)
        {
            lock (List)
                List.Insert(index, item);
        }

        public void RemoveAt(int index)
        {
            lock (List)
                List.RemoveAt(index);
        }

        public LogEntry this[int index]
        {
            get
            {
                lock (List)
                    return List[index];
            }
            set
            {
                lock (List)
                    List[index] = value;
            }
        }

        #endregion

        #region ICollection<LogEntry> Members

        public void Add(LogEntry item)
        {
            lock (List)
                List.Add(item);
        }

        public void Clear()
        {
            lock (List)
                List.Clear();
        }

        public bool Contains(LogEntry item)
        {
            lock (List)
                return List.Contains(item);
        }

        public void CopyTo(LogEntry[] array, int arrayIndex)
        {
            lock (List)
                List.CopyTo(array, arrayIndex);
        }

        public int Count
        {
            get
            {
                lock(List)
                    return Count;
            }
        }

        public bool IsReadOnly
        {
            get { return true; }
        }

        public bool Remove(LogEntry item)
        {
            lock (List)
                return List.Remove(item);
        }

        #endregion

        #region IEnumerable<LogEntry> Members

        public IEnumerator<LogEntry> GetEnumerator()
        {
            return List.GetEnumerator();
        }

        #endregion

        #region IEnumerable Members

        System.Collections.IEnumerator System.Collections.IEnumerable.GetEnumerator()
        {
            return List.GetEnumerator();
        }

        #endregion

        /// <summary>
        /// Gets the highest log level in the current log sink.
        /// </summary>
        public LogLevel Highest
        {
            get
            {
                lock (List)
                    return List.Max(delegate(LogEntry e) { return e.Level; });
            }
        }

        /// <summary>
        /// Gets the time the first message was logged.
        /// </summary>
        public DateTime StartTime
        {
            get
            {
                lock (List)
                    return List.First().Timestamp;
            }
        }

        /// <summary>
        /// Gets the time the last message was logged.
        /// </summary>
        public DateTime EndTime
        {
            get
            {
                lock (List)
                    return List.Last().Timestamp;
            }
        }

        /// <summary>
        /// The backing store of this session.
        /// </summary>
        private List<LogEntry> List = new List<LogEntry>();
    }
}