#region Apache License
//
// Licensed to the Apache Software Foundation (ASF) under one or more 
// contributor license agreements. See the NOTICE file distributed with
// this work for additional information regarding copyright ownership. 
// The ASF licenses this file to you 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 log4net;
using log4net.Core;

namespace log4net.Layout
{
	/// <summary>
	/// Extend this abstract class to create your own log layout format.
	/// </summary>
	/// <remarks>
	/// <para>
	/// This is the base implementation of the <see cref="ILayout"/>
	/// interface. Most layout objects should extend this class.
	/// </para>
	/// </remarks>
	/// <remarks>
	/// <note type="inheritinfo">
	/// <para>
	/// Subclasses must implement the <see cref="Format(TextWriter,LoggingEvent)"/>
	/// method.
	/// </para>
	/// <para>
	/// Subclasses should set the <see cref="IgnoresException"/> in their default
	/// constructor.
	/// </para>
	/// </note>
	/// </remarks>
	/// <author>Nicko Cadell</author>
	/// <author>Gert Driesen</author>
	public abstract class LayoutSkeleton : ILayout, IOptionHandler
	{
		#region Member Variables

		/// <summary>
		/// The header text
		/// </summary>
		/// <remarks>
		/// <para>
		/// See <see cref="Header"/> for more information.
		/// </para>
		/// </remarks>
		private string m_header = null;

		/// <summary>
		/// The footer text
		/// </summary>
		/// <remarks>
		/// <para>
		/// See <see cref="Footer"/> for more information.
		/// </para>
		/// </remarks>
		private string m_footer = null;

		/// <summary>
		/// Flag indicating if this layout handles exceptions
		/// </summary>
		/// <remarks>
		/// <para>
		/// <c>false</c> if this layout handles exceptions
		/// </para>
		/// </remarks>
		private bool m_ignoresException = true;

		#endregion

		#region Constructors

		/// <summary>
		/// Empty default constructor
		/// </summary>
		/// <remarks>
		/// <para>
		/// Empty default constructor
		/// </para>
		/// </remarks>
		protected LayoutSkeleton()
		{
		}

		#endregion

		#region Implementation of IOptionHandler

		/// <summary>
		/// Activate component options
		/// </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>
 		/// <para>
 		/// This method must be implemented by the subclass.
 		/// </para>
		/// </remarks>
		abstract public void ActivateOptions();

		#endregion

		#region Implementation of ILayout

		/// <summary>
		/// Implement this method to create your own layout format.
		/// </summary>
		/// <param name="writer">The TextWriter to write the formatted event to</param>
		/// <param name="loggingEvent">The event to format</param>
		/// <remarks>
		/// <para>
		/// This method is called by an appender to format
		/// the <paramref name="loggingEvent"/> as text.
		/// </para>
		/// </remarks>
		abstract public void Format(TextWriter writer, LoggingEvent loggingEvent);

        /// <summary>
        /// Convenience method for easily formatting the logging event into a string variable.
        /// </summary>
        /// <param name="loggingEvent"></param>
        /// <remarks>
        /// Creates a new StringWriter instance to store the formatted logging event.
        /// </remarks>
        public string Format(LoggingEvent loggingEvent)
        {
            StringWriter writer = new StringWriter(System.Globalization.CultureInfo.InvariantCulture);
            Format(writer, loggingEvent);
            return writer.ToString();
        }

	    /// <summary>
	    /// The content type output by this layout. 
	    /// </summary>
	    /// <value>The content type is <c>"text/plain"</c></value>
	    /// <remarks>
	    /// <para>
	    /// The content type output by this layout.
	    /// </para>
	    /// <para>
	    /// This base class uses the value <c>"text/plain"</c>.
	    /// To change this value a subclass must override this
	    /// property.
	    /// </para>
	    /// </remarks>
	    virtual public string ContentType
	    {
	        get { return "text/plain"; }
	    }

	    /// <summary>
	    /// The header for the layout format.
	    /// </summary>
	    /// <value>the layout header</value>
	    /// <remarks>
	    /// <para>
	    /// The Header text will be appended before any logging events
	    /// are formatted and appended.
	    /// </para>
	    /// </remarks>
	    virtual public string Header
	    {
	        get { return m_header; }
	        set { m_header = value; }
	    }

	    /// <summary>
	    /// The footer for the layout format.
	    /// </summary>
	    /// <value>the layout footer</value>
	    /// <remarks>
	    /// <para>
	    /// The Footer text will be appended after all the logging events
	    /// have been formatted and appended.
	    /// </para>
	    /// </remarks>
	    virtual public string Footer
	    {
	        get { return m_footer; }
	        set { m_footer = value; }
	    }

	    /// <summary>
	    /// Flag indicating if this layout handles exceptions
	    /// </summary>
	    /// <value><c>false</c> if this layout handles exceptions</value>
	    /// <remarks>
	    /// <para>
	    /// If this layout handles the exception object contained within
	    /// <see cref="LoggingEvent"/>, then the layout should return
	    /// <c>false</c>. Otherwise, if the layout ignores the exception
	    /// object, then the layout should return <c>true</c>.
	    /// </para>
	    /// <para>
	    /// Set this value to override a this default setting. The default
	    /// value is <c>true</c>, this layout does not handle the exception.
	    /// </para>
	    /// </remarks>
	    virtual public bool IgnoresException 
	    { 
	        get { return m_ignoresException; }
	        set { m_ignoresException = value; }
	    }

	    #endregion
	}
}
