#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.Reflection;

using log4net.Core;

namespace SampleAppendersApp.Appender
{
  /// <summary>
  /// Forwarding Appender that introspects the <see cref="LoggingEvent.MessageObject"/>
  /// and extracts all public properties and fields and stores them in the
  /// <see cref="LoggingEvent.Properties"/>
  /// </summary>
  public sealed class MessageObjectExpanderAppender : log4net.Appender.ForwardingAppender
  {
    /// <inheritdoc/>
    protected override void Append(LoggingEvent loggingEvent)
    {
      ArgumentNullException.ThrowIfNull(loggingEvent);
      object messageObject = loggingEvent.MessageObject;

      if (messageObject != null && !(messageObject is string))
      {
        Type messageType = messageObject.GetType();

        // Get all public instance properties
        if (ExpandProperties)
          foreach (PropertyInfo propertyInfo in messageType.GetProperties(BindingFlags.Instance | BindingFlags.Public))
            if (propertyInfo.CanRead)
              loggingEvent.Properties[propertyInfo.Name] = propertyInfo.GetValue(messageObject, null);

        // Get all public instance fields
        if (ExpandFields)
          foreach (FieldInfo fieldInfo in messageType.GetFields(BindingFlags.Instance | BindingFlags.Public))
            loggingEvent.Properties[fieldInfo.Name] = fieldInfo.GetValue(messageObject);
      }

      // Delegate to base class which will forward
      base.Append(loggingEvent);
    }

    /// <inheritdoc/>
    public bool ExpandProperties { get; set; } = true;

    /// <inheritdoc/>
    public bool ExpandFields { get; set; } = true;
  }
}