#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 log4net.Layout;
using log4net.Core;
using log4net.Util;

namespace log4net.Appender
{
  /// <summary>
  /// Appends logging events to the console.
  /// </summary>
  /// <remarks>
  /// <para>
  /// ConsoleAppender appends log events to the standard output stream
  /// or the error output stream using a layout specified by the 
  /// user.
  /// </para>
  /// <para>
  /// By default, all output is written to the console's standard output stream.
  /// The <see cref="Target"/> property can be set to direct the output to the
  /// error stream.
  /// </para>
  /// <para>
  /// NOTE: This appender writes each message to the <c>System.Console.Out</c> or 
  /// <c>System.Console.Error</c> that is set at the time the event is appended.
  /// Therefore it is possible to programmatically redirect the output of this appender 
  /// (for example NUnit does this to capture program output). While this is the desired
  /// behavior of this appender it may have security implications in your application. 
  /// </para>
  /// </remarks>
  /// <author>Nicko Cadell</author>
  /// <author>Gert Driesen</author>
  public class ConsoleAppender : AppenderSkeleton
  {
    /// <summary>
    /// Initializes a new instance of the <see cref="ConsoleAppender" /> class.
    /// </summary>
    /// <remarks>
    /// The instance of the <see cref="ConsoleAppender" /> class is set up to write 
    /// to the standard output stream.
    /// </remarks>
    public ConsoleAppender()
    {
    }

    /// <summary>
    /// Target is the value of the console output stream.
    /// This is either <c>"Console.Out"</c> or <c>"Console.Error"</c>.
    /// </summary>
    /// <value>
    /// Target is the value of the console output stream.
    /// This is either <c>"Console.Out"</c> or <c>"Console.Error"</c>.
    /// </value>
    /// <remarks>
    /// <para>
    /// Target is the value of the console output stream.
    /// This is either <c>"Console.Out"</c> or <c>"Console.Error"</c>.
    /// </para>
    /// </remarks>
    public virtual string Target
    {
      get => m_writeToErrorStream ? ConsoleError : ConsoleOut;
      set => m_writeToErrorStream = SystemInfo.EqualsIgnoringCase(ConsoleError, value.Trim());
    }

    /// <summary>
    /// This method is called by the <see cref="M:AppenderSkeleton.DoAppend(LoggingEvent)"/> method.
    /// </summary>
    /// <param name="loggingEvent">The event to log.</param>
    /// <remarks>
    /// <para>
    /// Writes the event to the console.
    /// </para>
    /// <para>
    /// The format of the output will depend on the appender's layout.
    /// </para>
    /// </remarks>
    protected override void Append(LoggingEvent loggingEvent)
    {
      if (m_writeToErrorStream)
      {
        // Write to the error stream
        Console.Error.Write(RenderLoggingEvent(loggingEvent));
      }
      else
      {
        // Write to the output stream
        Console.Write(RenderLoggingEvent(loggingEvent));
      }
    }

    /// <summary>
    /// This appender requires a <see cref="Layout"/> to be set.
    /// </summary>
    protected override bool RequiresLayout => true;

    /// <summary>
    /// The <see cref="ConsoleAppender.Target"/> to use when writing to the Console 
    /// standard output stream.
    /// </summary>
    public const string ConsoleOut = "Console.Out";

    /// <summary>
    /// The <see cref="ConsoleAppender.Target"/> to use when writing to the Console 
    /// standard error output stream.
    /// </summary>
    public const string ConsoleError = "Console.Error";

    private bool m_writeToErrorStream;
  }
}
