#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 System.Runtime.InteropServices;

namespace log4net.Util.PatternStringConverters
{
  /// <summary>
  /// Write the current threads username to the output
  /// </summary>
  /// <remarks>
  /// <para>
  /// Write the current threads username to the output writer
  /// </para>
  /// </remarks>
  /// <author>Nicko Cadell</author>
  internal sealed class UserNamePatternConverter : PatternConverter
  {
    /// <summary>
    /// Write the current threads username to the output
    /// </summary>
    /// <param name="writer">the writer to write to</param>
    /// <param name="state">null, state is not set</param>
    /// <remarks>
    /// <para>
    /// Write the current threads username to the output <paramref name="writer"/>.
    /// </para>
    /// </remarks>
    public override void Convert(TextWriter writer, object? state)
    {
      try
      {
#if !NET462_OR_GREATER
        if (!RuntimeInformation.IsOSPlatform(OSPlatform.Windows))
        {
          Fallback(writer);
          return;
        }
#endif
        if (System.Security.Principal.WindowsIdentity.GetCurrent()?.Name is string name)
        {
          writer.Write(name);
        }
      }
      catch (System.Security.SecurityException)
      {
        Fallback(writer);
      }

      static void Fallback(TextWriter writer)
      {
        // This security exception will occur if the caller does not have 
        // some undefined set of SecurityPermission flags.
        LogLog.Debug(declaringType, "Security exception while trying to get current windows identity. Error Ignored.");
        writer.Write(SystemInfo.NotAvailableText);
      }
    }

    /// <summary>
    /// The fully qualified type of the UserNamePatternConverter class.
    /// </summary>
    /// <remarks>
    /// Used by the internal logger to record the Type of the
    /// log message.
    /// </remarks>
    private static readonly Type declaringType = typeof(UserNamePatternConverter);
  }
}