#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.Core;

namespace log4net.Layout
{
  /// <summary>
  /// A Layout that renders only the Exception text from the logging event
  /// </summary>
  /// <remarks>
  /// <para>
  /// This Layout should only be used with appenders that utilize multiple
  /// layouts (e.g. <see cref="log4net.Appender.AdoNetAppender"/>).
  /// </para>
  /// </remarks>
  /// <author>Nicko Cadell</author>
  /// <author>Gert Driesen</author>
  public class ExceptionLayout : LayoutSkeleton
  {
    /// <summary>
    /// Constructs an ExceptionLayout.
    /// </summary>
    public ExceptionLayout()
    {
      IgnoresException = false;
    }

    /// <summary>
    /// Activates component options.
    /// </summary>
    /// <remarks>
    /// <para>
    /// Part of the <see cref="IOptionHandler"/> component activation
    /// framework.
    /// </para>
    /// <para>
    /// This method does nothing as options become effective immediately.
    /// </para>
    /// </remarks>
    public override void ActivateOptions()
    {
      // nothing to do.
    }

    /// <summary>
    /// Gets the exception text from the logging event
    /// </summary>
    /// <param name="writer">The TextWriter to write the formatted event to</param>
    /// <param name="loggingEvent">the event being logged</param>
    /// <remarks>
    /// <para>
    /// Write the exception string to the <see cref="TextWriter"/>.
    /// The exception string is retrieved from <see cref="M:LoggingEvent.GetExceptionString()"/>.
    /// </para>
    /// </remarks>
    public override void Format(TextWriter writer, LoggingEvent loggingEvent)
    {
      if (loggingEvent is null)
      {
        throw new ArgumentNullException(nameof(loggingEvent));
      }

      writer.Write(loggingEvent.GetExceptionString());
    }
  }
}
