DP44/Common/DTS.Common.Utilities/TextLogger.WriteCycleHandle.cs

/*
 * TextLogger.WriteCycleHandle.cs
 * 
 * Copyright © 2010
 * Diversified Technical Systems, Inc.
 * All Rights Reserved.
 */

using System;
using System.Collections.Generic;
using System.Threading;

namespace DTS.Common.Utilities.Logging
{   // *** see TextLogger.cs ***
    public partial class TextLogger
    {
        /// <summary>
        /// "Handle" containing the state information for a log message write session.
        /// </summary>
        protected class WriteCycleHandle
        {
            /// <summary>
            /// The filename of the log file receiving the messages being supplied to this
            /// write session.
            /// </summary>
            public string FullLogFileName { get; set; }

            /// <summary>
            /// The <see cref="System.Threading.AutoResetEvent"/> whose "set" kicks off
            /// a write cycle.
            /// </summary>
            public AutoResetEvent CycleTrigger { get; set; }

            /// <summary>
            /// The <see cref="System.Threading.AutoResetEvent"/> that is signaled when
            /// a write cycle completes.
            /// </summary>
            public AutoResetEvent CycleCompletionTrigger { get; set; }

            /// <summary>
            /// The <see cref="Logging.TextLogger.WriteCycleExceptionHandler"/> to be
            /// invoked when the write cycle encounters an exception.
            /// </summary>
            public WriteCycleExceptionHandler OnWriteCycleException { get; set; }

            /// <summary>
            /// <see cref="bool"/> flag that controls whether or not the write cycle should
            /// auto-terminate whenever it encounters an exception.
            /// </summary>
            public bool TerminateCycleOnException { get; set; }

            private static readonly object MyLock = new object();
            /// <summary>
            /// Get/set the <see cref="bool"/> flag that will terminate the associated write cycle when set to 'true'.
            /// </summary>
            public bool TerminateWriteCycle
            {
                get
                {
                    try
                    {
                        lock (MyLock)
                        {
                            if (!_IsTerminateWriteCycleInitialized)
                                throw new ApplicationException("TerminateWriteCycle value has not been initialized");
                            else return _TerminateWriteCycle;
                        }
                    }
                    catch (Exception ex)
                    {
                        throw new ApplicationException("encountered problem getting value for property " + GetType().FullName + ".TerminateWriteCycle", ex);
                    }
                }
                set
                {
                    try
                    {
                        lock (MyLock)
                        {   //
                            // Set the termination flag and then kick off a cycle so it goes into
                            // effect asap.
                            //
                            _IsTerminateWriteCycleInitialized = true;
                            _TerminateWriteCycle = value;
                            if (_TerminateWriteCycle)
                                CycleTrigger.Set();
                        }
                    }
                    catch (Exception ex)
                    {
                        throw new ApplicationException("encountered problem setting value for property " + GetType().FullName + ".TerminateWriteCycle", ex);
                    }
                }
            }
            private bool _TerminateWriteCycle;
            private bool _IsTerminateWriteCycleInitialized = false;

            /// <summary>
            /// The actually queue of log message <see cref="string"/>s to be written to the active log file.
            /// </summary>
            public Queue<string> WriteQueue
            {
                get
                {
                    try
                    {
                        if (!_IsWriteQueueInitialized)
                            throw new ApplicationException("WriteQueue has not been initialized");
                        else return _WriteQueue;
                    }
                    catch (Exception ex)
                    {
                        throw new ApplicationException("encountered problem getting value for property " + GetType().FullName + ".WriteQueue", ex);
                    }
                }
                set
                {
                    try
                    {
                        _IsWriteQueueInitialized = true;
                        _WriteQueue = value;
                    }
                    catch (Exception ex)
                    {
                        throw new ApplicationException("encountered problem setting value for property " + GetType().FullName + ".WriteQueue", ex);
                    }
                }
            }
            private Queue<string> _WriteQueue = null;
            private bool _IsWriteQueueInitialized = false;

            /// <summary>
            /// Callback to be invoked when the write cycle has closed it's associated log file's
            /// write handle for the last time.
            /// </summary>
            public WriteCycleCallback OnWriteCycleTermination
            {
                get
                {
                    try
                    {
                        lock (MyLock)
                        {
                            return _OnWriteCycleTermination;
                        }
                    }
                    catch (Exception ex)
                    {
                        throw new ApplicationException("encountered problem getting value for property " + GetType().FullName + ".OnWriteCycleTermination", ex);
                    }
                }
                set
                {
                    try
                    {
                        lock (MyLock)
                        {   //
                            // Set the cycle termination callback.  If we're undergoing termination and there's 
                            // nothing left in the write queue, then go ahead and immediately call the termination
                            // callback.  Null the reference after the call so we don't accidentally somehow end up
                            // calling it twice.
                            //
                            _OnWriteCycleTermination = value;
                            if (_IsTerminateWriteCycleInitialized && _TerminateWriteCycle &&
                                _IsWriteQueueInitialized && _WriteQueue.Count <= 0)
                            {
                                _OnWriteCycleTermination(_WriteQueue);
                                _OnWriteCycleTermination = null;
                            }
                        }
                    }
                    catch (Exception ex)
                    {
                        throw new ApplicationException("encountered problem setting value for property " + GetType().FullName + ".OnWriteCycleTermination", ex);
                    }
                }
            }
            private WriteCycleCallback _OnWriteCycleTermination = null;

            /// <summary>
            /// Initialize an instance of the <see cref="Logging.TextLogger.WriteCycleHandle"/> class.
            /// </summary>
            /// 
            /// <param name="fullLogFileName">
            /// The filename of the log file receiving the messages being supplied to this
            /// write session.
            /// </param>
            /// 
            /// <param name="writeQueue">
            /// The actually queue of log message <see cref="string"/>s to be written to the active log file.
            /// </param>
            /// 
            /// <param name="onWriteCycleTermination">
            /// Callback to be invoked when the write cycle has closed it's associated log file's
            /// write handle for the last time.
            /// </param>
            /// 
            /// <param name="onWriteCycleException">
            /// Callback to be invoked when the write cycle has closed it's associated log file's
            /// write handle for the last time.
            /// </param>
            /// 
            /// <param name="terminateCycleOnException">
            /// <see cref="bool"/> flag that controls whether or not the write cycle should
            /// auto-terminate whenever it encounters an exception.
            /// </param>
            /// 
            public WriteCycleHandle(string fullLogFileName,
                                     Queue<string> writeQueue,
                                     WriteCycleCallback onWriteCycleTermination,
                                     WriteCycleExceptionHandler onWriteCycleException,
                                     bool terminateCycleOnException)
            {
                TerminateWriteCycle = false;
                FullLogFileName = fullLogFileName;
                WriteQueue = writeQueue;
                CycleTrigger = new AutoResetEvent(false);
                CycleCompletionTrigger = new AutoResetEvent(false);
                OnWriteCycleTermination = onWriteCycleTermination;
                OnWriteCycleException = onWriteCycleException;
                TerminateCycleOnException = terminateCycleOnException;
            }
        }
    }
}