#region Copyright & License
//
// Copyright 2001-2005 The Apache Software Foundation
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//
#endregion

using System;
using System.IO;
using System.Collections;

using log4net.Filter;
using log4net.Util;
using log4net.Layout;
using log4net.Core;

namespace log4net.Appender
{
	/// <summary>
	/// Abstract base class implementation of <see cref="IAppender"/>. 
	/// </summary>
	/// <remarks>
	/// <para>
	/// This class provides the code for common functionality, such 
	/// as support for threshold filtering and support for general filters.
	/// </para>
	/// <para>
	/// Appenders can also implement the <see cref="IOptionHandler"/> interface. Therefore
	/// they would require that the <see cref="IOptionHandler.ActivateOptions()"/> method
	/// be called after the appenders properties have been configured.
	/// </para>
	/// </remarks>
	/// <author>Nicko Cadell</author>
	/// <author>Gert Driesen</author>
	public abstract class AppenderSkeleton : IAppender, IBulkAppender, IOptionHandler
	{
		#region Protected Instance Constructors

		/// <summary>
		/// Default constructor
		/// </summary>
		/// <remarks>
		/// <para>Empty default constructor</para>
		/// </remarks>
		protected AppenderSkeleton()
		{
			m_errorHandler = new OnlyOnceErrorHandler(this.GetType().Name);
		}

		#endregion Protected Instance Constructors

		#region Finalizer

		/// <summary>
		/// Finalizes this appender by calling the implementation's 
		/// <see cref="Close"/> method.
		/// </summary>
		/// <remarks>
		/// <para>
		/// If this appender has not been closed then the <c>Finalize</c> method
		/// will call <see cref="Close"/>.
		/// </para>
		/// </remarks>
		~AppenderSkeleton() 
		{
			// An appender might be closed then garbage collected. 
			// There is no point in closing twice.
			if (!m_closed) 
			{
				LogLog.Debug("AppenderSkeleton: Finalizing appender named ["+m_name+"].");
				Close();
			}
		}

		#endregion Finalizer

		#region Public Instance Properties

		/// <summary>
		/// Gets or sets the threshold <see cref="Level"/> of this appender.
		/// </summary>
		/// <value>
		/// The threshold <see cref="Level"/> of the appender. 
		/// </value>
		/// <remarks>
		/// <para>
		/// All log events with lower level than the threshold level are ignored 
		/// by the appender.
		/// </para>
		/// <para>
		/// In configuration files this option is specified by setting the
		/// value of the <see cref="Threshold"/> option to a level
		/// string, such as "DEBUG", "INFO" and so on.
		/// </para>
		/// </remarks>
		public Level Threshold 
		{
			get { return m_threshold; }
			set { m_threshold = value; }
		}

		/// <summary>
		/// Gets or sets the <see cref="IErrorHandler"/> for this appender.
		/// </summary>
		/// <value>The <see cref="IErrorHandler"/> of the appender</value>
		/// <remarks>
		/// <para>
		/// The <see cref="AppenderSkeleton"/> provides a default 
		/// implementation for the <see cref="ErrorHandler"/> property. 
		/// </para>
		/// </remarks>
		virtual public IErrorHandler ErrorHandler 
		{
			get { return this.m_errorHandler; }
			set 
			{
				lock(this) 
				{
					if (value == null) 
					{
						// We do not throw exception here since the cause is probably a
						// bad config file.
						LogLog.Warn("AppenderSkeleton: You have tried to set a null error-handler.");
					} 
					else 
					{
						m_errorHandler = value;
					}
				}
			}
		}

		/// <summary>
		/// The filter chain.
		/// </summary>
		/// <value>The head of the filter chain filter chain.</value>
		/// <remarks>
		/// <para>
		/// Returns the head Filter. The Filters are organized in a linked list
		/// and so all Filters on this Appender are available through the result.
		/// </para>
		/// </remarks>
		virtual public IFilter FilterHead
		{
			get { return m_headFilter; }
		}

		/// <summary>
		/// Gets or sets the <see cref="ILayout"/> for this appender.
		/// </summary>
		/// <value>The layout of the appender.</value>
		/// <remarks>
		/// <para>
		/// See <see cref="RequiresLayout"/> for more information.
		/// </para>
		/// </remarks>
		/// <seealso cref="RequiresLayout"/>
		virtual public ILayout Layout 
		{
			get { return m_layout; }
			set { m_layout = value; }
		}

		#endregion

		#region Implementation of IOptionHandler

		/// <summary>
		/// Initialize the appender based on the options set
		/// </summary>
		/// <remarks>
		/// <para>
		/// This is part of the <see cref="IOptionHandler"/> delayed object
		/// activation scheme. The <see cref="ActivateOptions"/> method must 
		/// be called on this object after the configuration properties have
		/// been set. Until <see cref="ActivateOptions"/> is called this
		/// object is in an undefined state and must not be used. 
		/// </para>
		/// <para>
		/// If any of the configuration properties are modified then 
		/// <see cref="ActivateOptions"/> must be called again.
		/// </para>
		/// </remarks>
		virtual public void ActivateOptions() 
		{
		}

		#endregion Implementation of IOptionHandler

		#region Implementation of IAppender

		/// <summary>
		/// Gets or sets the name of this appender.
		/// </summary>
		/// <value>The name of the appender.</value>
		/// <remarks>
		/// <para>
		/// The name uniquely identifies the appender.
		/// </para>
		/// </remarks>
		public string Name 
		{
			get { return m_name; }
			set { m_name = value; }
		}

		/// <summary>
		/// Closes the appender and release resources.
		/// </summary>
		/// <remarks>
		/// <para>
		/// Release any resources allocated within the appender such as file handles, 
		/// network connections, etc.
		/// </para>
		/// <para>
		/// It is a programming error to append to a closed appender.
		/// </para>
		/// <para>
		/// This method cannot be overridden by subclasses. This method 
		/// delegates the closing of the appender to the <see cref="OnClose"/>
		/// method which must be overridden in the subclass.
		/// </para>
		/// </remarks>
		public void Close()
		{
			// This lock prevents the appender being closed while it is still appending
			lock(this)
			{
				if (!m_closed)
				{
					OnClose();
					m_closed = true;
				}
			}
		}

		/// <summary>
		/// Performs threshold checks and invokes filters before 
		/// delegating actual logging to the subclasses specific 
		/// <see cref="Append(LoggingEvent)"/> method.
		/// </summary>
		/// <param name="loggingEvent">The event to log.</param>
		/// <remarks>
		/// <para>
		/// This method cannot be overridden by derived classes. A
		/// derived class should override the <see cref="Append(LoggingEvent)"/> method
		/// which is called by this method.
		/// </para>
		/// <para>
		/// The implementation of this method is as follows:
		/// </para>
		/// <para>
		/// <list type="bullet">
		///		<item>
		///			<description>
		///			Checks that the severity of the <paramref name="loggingEvent"/>
		///			is greater than or equal to the <see cref="Threshold"/> of this
		///			appender.</description>
		///		</item>
		///		<item>
		///			<description>
		///			Checks that the <see cref="IFilter"/> chain accepts the 
		///			<paramref name="loggingEvent"/>.
		///			</description>
		///		</item>
		///		<item>
		///			<description>
		///			Calls <see cref="PreAppendCheck()"/> and checks that 
		///			it returns <c>true</c>.</description>
		///		</item>
		/// </list>
		/// </para>
		/// <para>
		/// If all of the above steps succeed then the <paramref name="loggingEvent"/>
		/// will be passed to the abstract <see cref="Append(LoggingEvent)"/> method.
		/// </para>
		/// </remarks>
		public void DoAppend(LoggingEvent loggingEvent) 
		{
			// This lock is absolutely critical for correct formatting
			// of the message in a multi-threaded environment.  Without
			// this, the message may be broken up into elements from
			// multiple thread contexts (like get the wrong thread ID).

			lock(this)
			{
				if (m_closed)
				{
					ErrorHandler.Error("Attempted to append to closed appender named ["+m_name+"].");
					return;
				}

				// prevent re-entry
				if (m_recursiveGuard)
				{
					return;
				}

				try
				{
					m_recursiveGuard = true;

					if (FilterEvent(loggingEvent) && PreAppendCheck())
					{
						this.Append(loggingEvent);
					}
				}
				catch(Exception ex)
				{
					ErrorHandler.Error("Failed in DoAppend", ex);
				}
#if !MONO && !NET_2_0
				// on .NET 2.0 (and higher) and Mono (all profiles), 
				// exceptions that do not derive from System.Exception will be
				// wrapped in a RuntimeWrappedException by the runtime, and as
				// such will be catched by the catch clause above
				catch
				{
					// Catch handler for non System.Exception types
					ErrorHandler.Error("Failed in DoAppend (unknown exception)");
				}
#endif
				finally
				{
					m_recursiveGuard = false;
				}
			}
		}

		#endregion Implementation of IAppender

		#region Implementation of IBulkAppender

		/// <summary>
		/// Performs threshold checks and invokes filters before 
		/// delegating actual logging to the subclasses specific 
		/// <see cref="Append(LoggingEvent[])"/> method.
		/// </summary>
		/// <param name="loggingEvents">The array of events to log.</param>
		/// <remarks>
		/// <para>
		/// This method cannot be overridden by derived classes. A
		/// derived class should override the <see cref="Append(LoggingEvent[])"/> method
		/// which is called by this method.
		/// </para>
		/// <para>
		/// The implementation of this method is as follows:
		/// </para>
		/// <para>
		/// <list type="bullet">
		///		<item>
		///			<description>
		///			Checks that the severity of the <paramref name="loggingEvent"/>
		///			is greater than or equal to the <see cref="Threshold"/> of this
		///			appender.</description>
		///		</item>
		///		<item>
		///			<description>
		///			Checks that the <see cref="IFilter"/> chain accepts the 
		///			<paramref name="loggingEvent"/>.
		///			</description>
		///		</item>
		///		<item>
		///			<description>
		///			Calls <see cref="PreAppendCheck()"/> and checks that 
		///			it returns <c>true</c>.</description>
		///		</item>
		/// </list>
		/// </para>
		/// <para>
		/// If all of the above steps succeed then the <paramref name="loggingEvents"/>
		/// will be passed to the <see cref="Append(LoggingEvent[])"/> method.
		/// </para>
		/// </remarks>
		public void DoAppend(LoggingEvent[] loggingEvents) 
		{
			// This lock is absolutely critical for correct formatting
			// of the message in a multi-threaded environment.  Without
			// this, the message may be broken up into elements from
			// multiple thread contexts (like get the wrong thread ID).

			lock(this)
			{
				if (m_closed)
				{
					ErrorHandler.Error("Attempted to append to closed appender named ["+m_name+"].");
					return;
				}

				// prevent re-entry
				if (m_recursiveGuard)
				{
					return;
				}

				try
				{
					m_recursiveGuard = true;

					ArrayList filteredEvents = new ArrayList(loggingEvents.Length);

					foreach(LoggingEvent loggingEvent in loggingEvents)
					{
						if (FilterEvent(loggingEvent))
						{
							filteredEvents.Add(loggingEvent);
						}
					}

					if (filteredEvents.Count > 0 && PreAppendCheck())
					{
						this.Append((LoggingEvent[])filteredEvents.ToArray(typeof(LoggingEvent)));
					}
				}
				catch(Exception ex)
				{
					ErrorHandler.Error("Failed in Bulk DoAppend", ex);
				}
#if !MONO && !NET_2_0
				// on .NET 2.0 (and higher) and Mono (all profiles), 
				// exceptions that do not derive from System.Exception will be
				// wrapped in a RuntimeWrappedException by the runtime, and as
				// such will be catched by the catch clause above
				catch
				{
					// Catch handler for non System.Exception types
					ErrorHandler.Error("Failed in Bulk DoAppend (unknown exception)");
				}
#endif
				finally