#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.Core;

namespace log4net;

/// <summary>
/// The ILog interface is use by application to log messages into
/// the log4net framework.
/// </summary>
/// <remarks>
/// <para>
/// Use the <see cref="LogManager"/> to obtain logger instances
/// that implement this interface. The <see cref="M:LogManager.GetLogger(Assembly,Type)"/>
/// static method is used to get logger instances.
/// </para>
/// <para>
/// This class contains methods for logging at different levels and also
/// has properties for determining if those logging levels are
/// enabled in the current configuration.
/// </para>
/// <para>
/// This interface can be implemented in different ways. This documentation
/// specifies reasonable behavior that a caller can expect from the actual
/// implementation, however different implementations reserve the right to
/// do things differently.
/// </para>
/// </remarks>
/// <example>Simple example of logging messages
/// <code lang="C#">
/// ILog log = LogManager.GetLogger("application-log");
/// 
/// log.Info("Application Start");
/// log.Debug("This is a debug message");
/// 
/// if (log.IsDebugEnabled)
/// {
///    log.Debug("This is another debug message");
/// }
/// </code>
/// </example>
/// <seealso cref="LogManager"/>
/// <seealso cref="M:LogManager.GetLogger(Assembly, Type)"/>
/// <author>Nicko Cadell</author>
/// <author>Gert Driesen</author>
public interface ILog : ILoggerWrapper
{
  /// <overloads>Log a message object with the <see cref="Level.Debug"/> level.</overloads>
  /// <summary>
  /// Logs a message object with the <see cref="Level.Debug"/> level.
  /// </summary>
  /// <param name="message">The message object to log.</param>
  /// <remarks>
  /// <para>
  /// This method first checks if this logger is <c>DEBUG</c>
  /// enabled by comparing the level of this logger with the 
  /// <see cref="Level.Debug"/> level. If this logger is
  /// <c>DEBUG</c> enabled, then it converts the message object
  /// (passed as parameter) to a string by invoking the appropriate
  /// <see cref="log4net.ObjectRenderer.IObjectRenderer"/>. It then 
  /// proceeds to call all the registered appenders in this logger 
  /// and also higher in the hierarchy depending on the value of 
  /// the additivity flag.
  /// </para>
  /// <para><b>WARNING</b> Note that passing an <see cref="Exception"/> 
  /// to this method will print the name of the <see cref="Exception"/> 
  /// but no stack trace. To print a stack trace use the 
  /// <see cref="M:Debug(object,Exception)"/> form instead.
  /// </para>
  /// </remarks>
  /// <seealso cref="M:Debug(object,Exception)"/>
  /// <seealso cref="IsDebugEnabled"/>
  void Debug(object? message);

  /// <summary>
  /// Log a message object with the <see cref="Level.Debug"/> level including
  /// the stack trace of the <see cref="Exception"/> passed
  /// as a parameter.
  /// </summary>
  /// <param name="message">The message object to log.</param>
  /// <param name="exception">The exception to log, including its stack trace.</param>
  /// <remarks>
  /// <para>
  /// See the <see cref="M:Debug(object)"/> form for more detailed information.
  /// </para>
  /// </remarks>
  /// <seealso cref="M:Debug(object)"/>
  /// <seealso cref="IsDebugEnabled"/>
  void Debug(object? message, Exception? exception);

  /// <overloads>Log a formatted string with the <see cref="Level.Debug"/> level.</overloads>
  /// <summary>
  /// Logs a formatted message string with the <see cref="Level.Debug"/> level.
  /// </summary>
  /// <param name="format">A String containing zero or more format items</param>
  /// <param name="args">An Object array containing zero or more objects to format</param>
  /// <remarks>
  /// <para>
  /// The message is formatted using the <c>String.Format</c> method. See
  /// <see cref="M:String.Format(string, object[])"/> for details of the syntax of the format string and the behavior
  /// of the formatting.
  /// </para>
  /// <para>
  /// This method does not take an <see cref="Exception"/> object to include in the
  /// log event. To pass an <see cref="Exception"/> use one of the <see cref="M:Debug(object,Exception)"/>
  /// methods instead.
  /// </para>
  /// </remarks>
  /// <seealso cref="M:Debug(object)"/>
  /// <seealso cref="IsDebugEnabled"/>
  void DebugFormat(string format, params object?[]? args);

  /// <summary>
  /// Logs a formatted message string with the <see cref="Level.Debug"/> level.
  /// </summary>
  /// <param name="format">A String containing zero or more format items</param>
  /// <param name="arg0">An Object to format</param>
  /// <remarks>
  /// <para>
  /// The message is formatted using the <c>String.Format</c> method. See
  /// <see cref="M:String.Format(string, object[])"/> for details of the syntax of the format string and the behavior
  /// of the formatting.
  /// </para>
  /// <para>
  /// This method does not take an <see cref="Exception"/> object to include in the
  /// log event. To pass an <see cref="Exception"/> use one of the <see cref="M:Debug(object,Exception)"/>
  /// methods instead.
  /// </para>
  /// </remarks>
  /// <seealso cref="M:Debug(object)"/>
  /// <seealso cref="IsDebugEnabled"/>
  void DebugFormat(string format, object? arg0);

  /// <summary>
  /// Logs a formatted message string with the <see cref="Level.Debug"/> level.
  /// </summary>
  /// <param name="format">A String containing zero or more format items</param>
  /// <param name="arg0">An Object to format</param>
  /// <param name="arg1">An Object to format</param>
  /// <remarks>
  /// <para>
  /// The message is formatted using the <c>String.Format</c> method. See
  /// <see cref="M:String.Format(string, object[])"/> for details of the syntax of the format string and the behavior
  /// of the formatting.
  /// </para>
  /// <para>
  /// This method does not take an <see cref="Exception"/> object to include in the
  /// log event. To pass an <see cref="Exception"/> use one of the <see cref="M:Debug(object,Exception)"/>
  /// methods instead.
  /// </para>
  /// </remarks>
  /// <seealso cref="M:Debug(object)"/>
  /// <seealso cref="IsDebugEnabled"/>
  void DebugFormat(string format, object? arg0, object? arg1);

  /// <summary>
  /// Logs a formatted message string with the <see cref="Level.Debug"/> level.
  /// </summary>
  /// <param name="format">A String containing zero or more format items</param>
  /// <param name="arg0">An Object to format</param>
  /// <param name="arg1">An Object to format</param>
  /// <param name="arg2">An Object to format</param>
  /// <remarks>
  /// <para>
  /// The message is formatted using the <c>String.Format</c> method. See
  /// <see cref="M:String.Format(string, object[])"/> for details of the syntax of the format string and the behavior
  /// of the formatting.
  /// </para>
  /// <para>
  /// This method does not take an <see cref="Exception"/> object to include in the
  /// log event. To pass an <see cref="Exception"/> use one of the <see cref="M:Debug(object,Exception)"/>
  /// methods instead.
  /// </para>
  /// </remarks>
  /// <seealso cref="M:Debug(object)"/>
  /// <seealso cref="IsDebugEnabled"/>
  void DebugFormat(string format, object? arg0, object? arg1, object? arg2);

  /// <summary>
  /// Logs a formatted message string with the <see cref="Level.Debug"/> level.
  /// </summary>
  /// <param name="provider">An <see cref="IFormatProvider"/> that supplies culture-specific formatting information</param>
  /// <param name="format">A String containing zero or more format items</param>
  /// <param name="args">An Object array containing zero or more objects to format</param>
  /// <remarks>
  /// <para>
  /// The message is formatted using the <c>String.Format</c> method. See
  /// <see cref="M:String.Format(string, object[])"/> for details of the syntax of the format string and the behavior
  /// of the formatting.
  /// </para>
  /// <para>
  /// This method does not take an <see cref="Exception"/> object to include in the
  /// log event. To pass an <see cref="Exception"/> use one of the <see cref="M:Debug(object,Exception)"/>
  /// methods instead.
  /// </para>
  /// </remarks>
  /// <seealso cref="M:Debug(object)"/>
  /// <seealso cref="IsDebugEnabled"/>
  void DebugFormat(IFormatProvider? provider, string format, params object?[]? args);

  /// <overloads>Log a message object with the <see cref="Level.Info"/> level.</overloads>
  /// <summary>
  /// Logs a message object with the <see cref="Level.Info"/> level.
  /// </summary>
  /// <remarks>
  /// <para>
  /// This method first checks if this logger is <c>INFO</c>
  /// enabled by comparing the level of this logger with the 
  /// <see cref="Level.Info"/> level. If this logger is
  /// <c>INFO</c> enabled, then it converts the message object
  /// (passed as parameter) to a string by invoking the appropriate
  /// <see cref="log4net.ObjectRenderer.IObjectRenderer"/>. It then 
  /// proceeds to call all the registered appenders in this logger 
  /// and also higher in the hierarchy depending on the value of the 
  /// additivity flag.
  /// </para>
  /// <para><b>WARNING</b> Note that passing an <see cref="Exception"/> 
  /// to this method will print the name of the <see cref="Exception"/> 
  /// but no stack trace. To print a stack trace use the 
  /// <see cref="M:Info(object,Exception)"/> form instead.
  /// </para>
  /// </remarks>
  /// <param name="message">The message object to log.</param>
  /// <seealso cref="M:Info(object,Exception)"/>
  /// <seealso cref="IsInfoEnabled"/>
  void Info(object? message);

  /// <summary>
  /// Logs a message object with the <c>INFO</c> level including
  /// the stack trace of the <see cref="Exception"/> passed
  /// as a parameter.
  /// </summary>
  /// <param name="message">The message object to log.</param>
  /// <param name="exception">The exception to log, including its stack trace.</param>
  /// <remarks>
  /// <para>
  /// See the <see cref="M:Info(object)"/> form for more detailed information.
  /// </para>
  /// </remarks>
  /// <seealso cref="M:Info(object)"/>
  /// <seealso cref="IsInfoEnabled"/>
  void Info(object? message, Exception? exception);

  /// <overloads>Log a formatted message string with the <see cref="Level.Info"/> level.</overloads>
  /// <summary>
  /// Logs a formatted message string with the <see cref="Level.Info"/> level.
  /// </summary>
  /// <param name="format">A String containing zero or more format items</param>
  /// <param name="args">An Object array containing zero or more objects to format</param>
  /// <remarks>
  /// <para>
  /// The message is formatted using the <c>String.Format</c> method. See
  /// <see cref="M:String.Format(string, object[])"/> for details of the syntax of the format string and the behavior
  /// of the formatting.
  /// </para>
  /// <para>
  /// This method does not take an <see cref="Exception"/> object to include in the
  /// log event. To pass an <see cref="Exception"/> use one of the <see cref="M:Info(object)"/>
  /// methods instead.
  /// </para>
  /// </remarks>
  /// <seealso cref="M:Info(object,Exception)"/>
  /// <seealso cref="IsInfoEnabled"/>
  void InfoFormat(string format, params object?[]? args);

  /// <summary>
  /// Logs a formatted message string with the <see cref="Level.Info"/> level.
  /// </summary>
  /// <param name="format">A String containing zero or more format items</param>
  /// <param name="arg0">An Object to format</param>
  /// <remarks>
  /// <para>
  /// The message is formatted using the <c>String.Format</c> method. See
  /// <see cref="M:String.Format(string, object[])"/> for details of the syntax of the format string and the behavior
  /// of the formatting.
  /// </para>
  /// <para>
  /// This method does not take an <see cref="Exception"/> object to include in the
  /// log event. To pass an <see cref="Exception"/> use one of the <see cref="M:Info(object,Exception)"/>
  /// methods instead.
  /// </para>
  /// </remarks>
  /// <seealso cref="M:Info(object)"/>
  /// <seealso cref="IsInfoEnabled"/>
  void InfoFormat(string format, object? arg0);

  /// <summary>
  /// Logs a formatted message string with the <see cref="Level.Info"/> level.
  /// </summary>
  /// <param name="format">A String containing zero or more format items</param>
  /// <param name="arg0">An Object to format</param>
  /// <param name="arg1">An Object to format</param>
  /// <remarks>
  /// <para>
  /// The message is formatted using the <c>String.Format</c> method. See
  /// <see cref="M:String.Format(string, object[])"/> for details of the syntax of the format string and the behavior
  /// of the formatting.
  /// </para>
  /// <para>
  /// This method does not take an <see cref="Exception"/> object to include in the
  /// log event. To pass an <see cref="Exception"/> use one of the <see cref="M:Info(object,Exception)"/>
  /// methods instead.
  /// </para>
  /// </remarks>
  /// <seealso cref="M:Info(object)"/>
  /// <seealso cref="IsInfoEnabled"/>
  void InfoFormat(string format, object? arg0, object? arg1);

  /// <summary>
  /// Logs a formatted message string with the <see cref="Level.Info"/> level.
  /// </summary>
  /// <param name="format">A String containing zero or more format items</param>
  /// <param name="arg0">An Object to format</param>
  /// <param name="arg1">An Object to format</param>
  /// <param name="arg2">An Object to format</param>
  /// <remarks>
  /// <para>
  /// The message is formatted using the <c>String.Format</c> method. See
  /// <see cref="M:String.Format(string, object[])"/> for details of the syntax of the format string and the behavior
  /// of the formatting.
  /// </para>
  /// <para>
  /// This method does not take an <see cref="Exception"/> object to include in the
  /// log event. To pass an <see cref="Exception"/> use one of the <see cref="M:Info(object,Exception)"/>
  /// methods instead.
  /// </para>
  /// </remarks>
  /// <seealso cref="M:Info(object)"/>
  /// <seealso cref="IsInfoEnabled"/>
  void InfoFormat(string format, object? arg0, object? arg1, object? arg2);

  /// <summary>
  /// Logs a formatted message string with the <see cref="Level.Info"/> level.
  /// </summary>
  /// <param name="provider">An <see cref="IFormatProvider"/> that supplies culture-specific formatting information</param>
  /// <param name="format">A String containing zero or more format items</param>
  /// <param name="args">An Object array containing zero or more objects to format</param>
  /// <remarks>
  /// <para>
  /// The message is formatted using the <c>String.Format</c> method. See
  /// <see cref="M:String.Format(string, object[])"/> for details of the syntax of the format string and the behavior
  /// of the formatting.
  /// </para>
  /// <para>
  /// This method does not take an <see cref="Exception"/> object to include in the
  /// log event. To pass an <see cref="Exception"/> use one of the <see cref="M:Info(object)"/>
  /// methods instead.
  /// </para>
  /// </remarks>
  /// <seealso cref="M:Info(object,Exception)"/>
  /// <seealso cref="IsInfoEnabled"/>
  void InfoFormat(IFormatProvider? provider, string format, params object?[]? args);

  /// <overloads>Log a message object with the <see cref="Level.Warn"/> level.</overloads>
  /// <summary>
  /// Log a message object with the <see cref="Level.Warn"/> level.
  /// </summary>
  /// <remarks>
  /// <para>
  /// This method first checks if this logger is <c>WARN</c>
  /// enabled by comparing the level of this logger with the 
  /// <see cref="Level.Warn"/> level. If this logger is
  /// <c>WARN</c> enabled, then it converts the message object
  /// (passed as parameter) to a string by invoking the appropriate
  /// <see cref="log4net.ObjectRenderer.IObjectRenderer"/>. It then 
  /// proceeds to call all the registered appenders in this logger 
  /// and also higher in the hierarchy depending on the value of the 
  /// additivity flag.
  /// </para>
  /// <para><b>WARNING</b> Note that passing an <see cref="Exception"/> 
  /// to this method will print the name of the <see cref="Exception"/> 
  /// but no stack trace. To print a stack trace use the 
  /// <see cref="M:Warn(object,Exception)"/> form instead.
  /// </para>
  /// </remarks>
  /// <param name="message">The message object to log.</param>
  /// <seealso cref="M:Warn(object,Exception)"/>
  /// <seealso cref="IsWarnEnabled"/>
  void Warn(object? message);

  /// <summary>
  /// Log a message object with the <see cref="Level.Warn"/> level including
  /// the stack trace of the <see cref="Exception"/> passed
  /// as a parameter.
  /// </summary>
  /// <param name="message">The message object to log.</param>
  /// <param name="exception">The exception to log, including its stack trace.</param>
  /// <remarks>
  /// <para>
  /// See the <see cref="M:Warn(object)"/> form for more detailed information.
  /// </para>
  /// </remarks>
  /// <seealso cref="M:Warn(object)"/>
  /// <seealso cref="IsWarnEnabled"/>
  void Warn(object? message, Exception? exception);

  /// <overloads>Log a formatted message string with the <see cref="Level.Warn"/> level.</overloads>
  /// <summary>
  /// Logs a formatted message string with the <see cref="Level.Warn"/> level.
  /// </summary>
  /// <param name="format">A String containing zero or more format items</param>
  /// <param name="args">An Object array containing zero or more objects to format</param>
  /// <remarks>
  /// <para>
  /// The message is formatted using the <c>String.Format</c> method. See
  /// <see cref="M:String.Format(string, object[])"/> for details of the syntax of the format string and the behavior
  /// of the formatting.
  /// </para>
  /// <para>
  /// This method does not take an <see cref="Exception"/> object to include in the
  /// log event. To pass an <see cref="Exception"/> use one of the <see cref="M:Warn(object)"/>
  /// methods instead.
  /// </para>
  /// </remarks>
  /// <seealso cref="M:Warn(object,Exception)"/>
  /// <seealso cref="IsWarnEnabled"/>
  void WarnFormat(string format, params object?[]? args);

  /// <summary>
  /// Logs a formatted message string with the <see cref="Level.Warn"/> level.
  /// </summary>
  /// <param name="format">A String containing zero or more format items</param>
  /// <param name="arg0">An Object to format</param>
  /// <remarks>
  /// <para>
  /// The message is formatted using the <c>String.Format</c> method. See
  /// <see cref="M:String.Format(string, object[])"/> for details of the syntax of the format string and the behavior
  /// of the formatting.
  /// </para>
  /// <para>
  /// This method does not take an <see cref="Exception"/> object to include in the
  /// log event. To pass an <see cref="Exception"/> use one of the <see cref="M:Warn(object,Exception)"/>
  /// methods instead.
  /// </para>
  /// </remarks>
  /// <seealso cref="M:Warn(object)"/>
  /// <seealso cref="IsWarnEnabled"/>
  void WarnFormat(string format, object? arg0);

  /// <summary>
  /// Logs a formatted message string with the <see cref="Level.Warn"/> level.
  /// </summary>
  /// <param name="format">A String containing zero or more format items</param>
  /// <param name="arg0">An Object to format</param>
  /// <param name="arg1">An Object to format</param>
  /// <remarks>
  /// <para>
  /// The message is formatted using the <c>String.Format</c> method. See
  /// <see cref="M:String.Format(string, object[])"/> for details of the syntax of the format string and the behavior
  /// of the formatting.
  /// </para>
  /// <para>
  /// This method does not take an <see cref="Exception"/> object to include in the
  /// log event. To pass an <see cref="Exception"/> use one of the <see cref="M:Warn(object,Exception)"/>
  /// methods instead.
  /// </para>
  /// </remarks>
  /// <seealso cref="M:Warn(object)"/>
  /// <seealso cref="IsWarnEnabled"/>
  void WarnFormat(string format, object? arg0, object? arg1);

  /// <summary>
  /// Logs a formatted message string with the <see cref="Level.Warn"/> level.
  /// </summary>
  /// <param name="format">A String containing zero or more format items</param>
  /// <param name="arg0">An Object to format</param>
  /// <param name="arg1">An Object to format</param>
  /// <param name="arg2">An Object to format</param>
  /// <remarks>
  /// <para>
  /// The message is formatted using the <c>String.Format</c> method. See
  /// <see cref="M:String.Format(string, object[])"/> for details of the syntax of the format string and the behavior
  /// of the formatting.
  /// </para>
  /// <para>
  /// This method does not take an <see cref="Exception"/> object to include in the
  /// log event. To pass an <see cref="Exception"/> use one of the <see cref="M:Warn(object,Exception)"/>
  /// methods instead.
  /// </para>
  /// </remarks>
  /// <seealso cref="M:Warn(object)"/>
  /// <seealso cref="IsWarnEnabled"/>
  void WarnFormat(string format, object? arg0, object? arg1, object? arg2);

  /// <summary>
  /// Logs a formatted message string with the <see cref="Level.Warn"/> level.
  /// </summary>
  /// <param name="provider">An <see cref="IFormatProvider"/> that supplies culture-specific formatting information</param>
  /// <param name="format">A String containing zero or more format items</param>
  /// <param name="args">An Object array containing zero or more objects to format</param>
  /// <remarks>
  /// <para>
  /// The message is formatted using the <c>String.Format</c> method. See
  /// <see cref="M:String.Format(string, object[])"/> for details of the syntax of the format string and the behavior
  /// of the formatting.
  /// </para>
  /// <para>
  /// This method does not take an <see cref="Exception"/> object to include in the
  /// log event. To pass an <see cref="Exception"/> use one of the <see cref="M:Warn(object)"/>
  /// methods instead.
  /// </para>
  /// </remarks>
  /// <seealso cref="M:Warn(object,Exception)"/>
  /// <seealso cref="IsWarnEnabled"/>
  void WarnFormat(IFormatProvider? provider, string format, params object?[]? args);

  /// <overloads>Log a message object with the <see cref="Level.Error"/> level.</overloads>
  /// <summary>
  /// Logs a message object with the <see cref="Level.Error"/> level.
  /// </summary>
  /// <param name="message">The message object to log.</param>
  /// <remarks>
  /// <para>
  /// This method first checks if this logger is <c>ERROR</c>
  /// enabled by comparing the level of this logger with the 
  /// <see cref="Level.Error"/> level. If this logger is
  /// <c>ERROR</c> enabled, then it converts the message object
  /// (passed as parameter) to a string by invoking the appropriate
  /// <see cref="log4net.ObjectRenderer.IObjectRenderer"/>. It then 
  /// proceeds to call all the registered appenders in this logger 
  /// and also higher in the hierarchy depending on the value of the 
  /// additivity flag.
  /// </para>
  /// <para><b>WARNING</b> Note that passing an <see cref="Exception"/> 
  /// to this method will print the name of the <see cref="Exception"/> 
  /// but no stack trace. To print a stack trace use the 
  /// <see cref="M:Error(object,Exception)"/> form instead.
  /// </para>
  /// </remarks>
  /// <seealso cref="M:Error(object,Exception)"/>
  /// <seealso cref="IsErrorEnabled"/>
  void Error(object? message);

  /// <summary>
  /// Log a message object with the <see cref="Level.Error"/> level including
  /// the stack trace of the <see cref="Exception"/> passed
  /// as a parameter.
  /// </summary>
  /// <param name="message">The message object to log.</param>
  /// <param name="exception">The exception to log, including its stack trace.</param>
  /// <remarks>
  /// <para>
  /// See the <see cref="M:Error(object)"/> form for more detailed information.
  /// </para>
  /// </remarks>
  /// <seealso cref="M:Error(object)"/>
  /// <seealso cref="IsErrorEnabled"/>
  void Error(object? message, Exception? exception);

  /// <overloads>Log a formatted message string with the <see cref="Level.Error"/> level.</overloads>
  /// <summary>
  /// Logs a formatted message string with the <see cref="Level.Error"/> level.
  /// </summary>
  /// <param name="format">A String containing zero or more format items</param>
  /// <param name="args">An Object array containing zero or more objects to format</param>
  /// <remarks>
  /// <para>
  /// The message is formatted using the <c>String.Format</c> method. See
  /// <see cref="M:String.Format(string, object[])"/> for details of the syntax of the format string and the behavior
  /// of the formatting.
  /// </para>
  /// <para>
  /// This method does not take an <see cref="Exception"/> object to include in the
  /// log event. To pass an <see cref="Exception"/> use one of the <see cref="M:Error(object)"/>
  /// methods instead.
  /// </para>
  /// </remarks>
  /// <seealso cref="M:Error(object,Exception)"/>
  /// <seealso cref="IsErrorEnabled"/>
  void ErrorFormat(string format, params object?[]? args);

  /// <summary>
  /// Logs a formatted message string with the <see cref="Level.Error"/> level.
  /// </summary>
  /// <param name="format">A String containing zero or more format items</param>
  /// <param name="arg0">An Object to format</param>
  /// <remarks>
  /// <para>
  /// The message is formatted using the <c>String.Format</c> method. See
  /// <see cref="M:String.Format(string, object[])"/> for details of the syntax of the format string and the behavior
  /// of the formatting.
  /// </para>
  /// <para>
  /// This method does not take an <see cref="Exception"/> object to include in the
  /// log event. To pass an <see cref="Exception"/> use one of the <see cref="M:Error(object,Exception)"/>
  /// methods instead.
  /// </para>
  /// </remarks>
  /// <seealso cref="M:Error(object)"/>
  /// <seealso cref="IsErrorEnabled"/>
  void ErrorFormat(string format, object? arg0);

  /// <summary>
  /// Logs a formatted message string with the <see cref="Level.Error"/> level.
  /// </summary>
  /// <param name="format">A String containing zero or more format items</param>
  /// <param name="arg0">An Object to format</param>
  /// <param name="arg1">An Object to format</param>
  /// <remarks>
  /// <para>
  /// The message is formatted using the <c>String.Format</c> method. See
  /// <see cref="M:String.Format(string, object[])"/> for details of the syntax of the format string and the behavior
  /// of the formatting.
  /// </para>
  /// <para>
  /// This method does not take an <see cref="Exception"/> object to include in the
  /// log event. To pass an <see cref="Exception"/> use one of the <see cref="M:Error(object,Exception)"/>
  /// methods instead.
  /// </para>
  /// </remarks>
  /// <seealso cref="M:Error(object)"/>
  /// <seealso cref="IsErrorEnabled"/>
  void ErrorFormat(string format, object? arg0, object? arg1);

  /// <summary>
  /// Logs a formatted message string with the <see cref="Level.Error"/> level.
  /// </summary>
  /// <param name="format">A String containing zero or more format items</param>
  /// <param name="arg0">An Object to format</param>
  /// <param name="arg1">An Object to format</param>
  /// <param name="arg2">An Object to format</param>
  /// <remarks>
  /// <para>
  /// The message is formatted using the <c>String.Format</c> method. See
  /// <see cref="M:String.Format(string, object[])"/> for details of the syntax of the format string and the behavior
  /// of the formatting.
  /// </para>
  /// <para>
  /// This method does not take an <see cref="Exception"/> object to include in the
  /// log event. To pass an <see cref="Exception"/> use one of the <see cref="M:Error(object,Exception)"/>
  /// methods instead.
  /// </para>
  /// </remarks>
  /// <seealso cref="M:Error(object)"/>
  /// <seealso cref="IsErrorEnabled"/>
  void ErrorFormat(string format, object? arg0, object? arg1, object? arg2);

  /// <summary>
  /// Logs a formatted message string with the <see cref="Level.Error"/> level.
  /// </summary>
  /// <param name="provider">An <see cref="IFormatProvider"/> that supplies culture-specific formatting information</param>
  /// <param name="format">A String containing zero or more format items</param>
  /// <param name="args">An Object array containing zero or more objects to format</param>
  /// <remarks>
  /// <para>
  /// The message is formatted using the <c>String.Format</c> method. See
  /// <see cref="M:String.Format(string, object[])"/> for details of the syntax of the format string and the behavior
  /// of the formatting.
  /// </para>
  /// <para>
  /// This method does not take an <see cref="Exception"/> object to include in the
  /// log event. To pass an <see cref="Exception"/> use one of the <see cref="M:Error(object)"/>
  /// methods instead.
  /// </para>
  /// </remarks>
  /// <seealso cref="M:Error(object,Exception)"/>
  /// <seealso cref="IsErrorEnabled"/>
  void ErrorFormat(IFormatProvider? provider, string format, params object?[]? args);

  /// <overloads>Log a message object with the <see cref="Level.Fatal"/> level.</overloads>
  /// <summary>
  /// Log a message object with the <see cref="Level.Fatal"/> level.
  /// </summary>
  /// <remarks>
  /// <para>
  /// This method first checks if this logger is <c>FATAL</c>
  /// enabled by comparing the level of this logger with the 
  /// <see cref="Level.Fatal"/> level. If this logger is
  /// <c>FATAL</c> enabled, then it converts the message object
  /// (passed as parameter) to a string by invoking the appropriate
  /// <see cref="log4net.ObjectRenderer.IObjectRenderer"/>. It then 
  /// proceeds to call all the registered appenders in this logger 
  /// and also higher in the hierarchy depending on the value of the 
  /// additivity flag.
  /// </para>
  /// <para><b>WARNING</b> Note that passing an <see cref="Exception"/> 
  /// to this method will print the name of the <see cref="Exception"/> 
  /// but no stack trace. To print a stack trace use the 
  /// <see cref="M:Fatal(object,Exception)"/> form instead.
  /// </para>
  /// </remarks>
  /// <param name="message">The message object to log.</param>
  /// <seealso cref="M:Fatal(object,Exception)"/>
  /// <seealso cref="IsFatalEnabled"/>
  void Fatal(object? message);

  /// <summary>
  /// Log a message object with the <see cref="Level.Fatal"/> level including
  /// the stack trace of the <see cref="Exception"/> passed
  /// as a parameter.
  /// </summary>
  /// <param name="message">The message object to log.</param>
  /// <param name="exception">The exception to log, including its stack trace.</param>
  /// <remarks>
  /// <para>
  /// See the <see cref="M:Fatal(object)"/> form for more detailed information.
  /// </para>
  /// </remarks>
  /// <seealso cref="M:Fatal(object)"/>
  /// <seealso cref="IsFatalEnabled"/>
  void Fatal(object? message, Exception? exception);

  /// <overloads>Log a formatted message string with the <see cref="Level.Fatal"/> level.</overloads>
  /// <summary>
  /// Logs a formatted message string with the <see cref="Level.Fatal"/> level.
  /// </summary>
  /// <param name="format">A String containing zero or more format items</param>
  /// <param name="args">An Object array containing zero or more objects to format</param>
  /// <remarks>
  /// <para>
  /// The message is formatted using the <c>String.Format</c> method. See
  /// <see cref="M:String.Format(string, object[])"/> for details of the syntax of the format string and the behavior
  /// of the formatting.
  /// </para>
  /// <para>
  /// This method does not take an <see cref="Exception"/> object to include in the
  /// log event. To pass an <see cref="Exception"/> use one of the <see cref="M:Fatal(object)"/>
  /// methods instead.
  /// </para>
  /// </remarks>
  /// <seealso cref="M:Fatal(object,Exception)"/>
  /// <seealso cref="IsFatalEnabled"/>
  void FatalFormat(string format, params object?[]? args);

  /// <summary>
  /// Logs a formatted message string with the <see cref="Level.Fatal"/> level.
  /// </summary>
  /// <param name="format">A String containing zero or more format items</param>
  /// <param name="arg0">An Object to format</param>
  /// <remarks>
  /// <para>
  /// The message is formatted using the <c>String.Format</c> method. See
  /// <see cref="M:String.Format(string, object[])"/> for details of the syntax of the format string and the behavior
  /// of the formatting.
  /// </para>
  /// <para>
  /// This method does not take an <see cref="Exception"/> object to include in the
  /// log event. To pass an <see cref="Exception"/> use one of the <see cref="M:Fatal(object,Exception)"/>
  /// methods instead.
  /// </para>
  /// </remarks>
  /// <seealso cref="M:Fatal(object)"/>
  /// <seealso cref="IsFatalEnabled"/>
  void FatalFormat(string format, object? arg0);

  /// <summary>
  /// Logs a formatted message string with the <see cref="Level.Fatal"/> level.
  /// </summary>
  /// <param name="format">A String containing zero or more format items</param>
  /// <param name="arg0">An Object to format</param>
  /// <param name="arg1">An Object to format</param>
  /// <remarks>
  /// <para>
  /// The message is formatted using the <c>String.Format</c> method. See
  /// <see cref="M:String.Format(string, object[])"/> for details of the syntax of the format string and the behavior
  /// of the formatting.
  /// </para>
  /// <para>
  /// This method does not take an <see cref="Exception"/> object to include in the
  /// log event. To pass an <see cref="Exception"/> use one of the <see cref="M:Fatal(object,Exception)"/>
  /// methods instead.
  /// </para>
  /// </remarks>
  /// <seealso cref="M:Fatal(object)"/>
  /// <seealso cref="IsFatalEnabled"/>
  void FatalFormat(string format, object? arg0, object? arg1);

  /// <summary>
  /// Logs a formatted message string with the <see cref="Level.Fatal"/> level.
  /// </summary>
  /// <param name="format">A String containing zero or more format items</param>
  /// <param name="arg0">An Object to format</param>
  /// <param name="arg1">An Object to format</param>
  /// <param name="arg2">An Object to format</param>
  /// <remarks>
  /// <para>
  /// The message is formatted using the <c>String.Format</c> method. See
  /// <see cref="M:String.Format(string, object[])"/> for details of the syntax of the format string and the behavior
  /// of the formatting.
  /// </para>
  /// <para>
  /// This method does not take an <see cref="Exception"/> object to include in the
  /// log event. To pass an <see cref="Exception"/> use one of the <see cref="M:Fatal(object,Exception)"/>
  /// methods instead.
  /// </para>
  /// </remarks>
  /// <seealso cref="M:Fatal(object)"/>
  /// <seealso cref="IsFatalEnabled"/>
  void FatalFormat(string format, object? arg0, object? arg1, object? arg2);

  /// <summary>
  /// Logs a formatted message string with the <see cref="Level.Fatal"/> level.
  /// </summary>
  /// <param name="provider">An <see cref="IFormatProvider"/> that supplies culture-specific formatting information</param>
  /// <param name="format">A String containing zero or more format items</param>
  /// <param name="args">An Object array containing zero or more objects to format</param>
  /// <remarks>
  /// <para>
  /// The message is formatted using the <c>String.Format</c> method. See
  /// <see cref="M:String.Format(string, object[])"/> for details of the syntax of the format string and the behavior
  /// of the formatting.
  /// </para>
  /// <para>
  /// This method does not take an <see cref="Exception"/> object to include in the
  /// log event. To pass an <see cref="Exception"/> use one of the <see cref="M:Fatal(object)"/>
  /// methods instead.
  /// </para>
  /// </remarks>
  /// <seealso cref="M:Fatal(object,Exception)"/>
  /// <seealso cref="IsFatalEnabled"/>
  void FatalFormat(IFormatProvider? provider, string format, params object?[]? args);

  /// <summary>
  /// Checks if this logger is enabled for the <see cref="Level.Debug"/> level.
  /// </summary>
  /// <value>
  /// <c>true</c> if this logger is enabled for <see cref="Level.Debug"/> events, <c>false</c> otherwise.
  /// </value>
  /// <remarks>
  /// <para>
  /// This function is intended to lessen the computational cost of
  /// disabled log debug statements.
  /// </para>
  /// <para> For some ILog interface <c>log</c>, when you write:</para>
  /// <code lang="C#">
  /// log.Debug("This is entry number: " + i );
  /// </code>
  /// <para>
  /// You incur the cost constructing the message, string construction and concatenation in
  /// this case, regardless of whether the message is logged or not.
  /// </para>
  /// <para>
  /// If you are worried about speed (who isn't), then you should write:
  /// </para>
  /// <code lang="C#">
  /// if (log.IsDebugEnabled)
  /// { 
  ///     log.Debug("This is entry number: " + i );
  /// }
  /// </code>
  /// <para>
  /// This way you will not incur the cost of parameter
  /// construction if debugging is disabled for <c>log</c>. On
  /// the other hand, if the <c>log</c> is debug enabled, you
  /// will incur the cost of evaluating whether the logger is debug
  /// enabled twice. Once in <see cref="IsDebugEnabled"/> and once in
  /// the <see cref="M:Debug(object)"/>.  This is an insignificant overhead
  /// since evaluating a logger takes about 1% of the time it
  /// takes to actually log. This is the preferred style of logging.
  /// </para>
  /// <para>Alternatively if your logger is available statically then the is debug
  /// enabled state can be stored in a static variable like this:
  /// </para>
  /// <code lang="C#">
  /// private static readonly bool isDebugEnabled = log.IsDebugEnabled;
  /// </code>
  /// <para>
  /// Then when you come to log you can write:
  /// </para>
  /// <code lang="C#">
  /// if (isDebugEnabled)
  /// { 
  ///     log.Debug("This is entry number: " + i );
  /// }
  /// </code>
  /// <para>
  /// This way the debug enabled state is only queried once
  /// when the class is loaded. Using a <c>private static readonly</c>
  /// variable is the most efficient because it is a run time constant
  /// and can be heavily optimized by the JIT compiler.
  /// </para>
  /// <para>
  /// Of course if you use a static readonly variable to
  /// hold the enabled state of the logger then you cannot
  /// change the enabled state at runtime to vary the logging
  /// that is produced. You have to decide if you need absolute
  /// speed or runtime flexibility.
  /// </para>
  /// </remarks>
  /// <seealso cref="M:Debug(object)"/>
  /// <seealso cref="M:DebugFormat(IFormatProvider, string, object[])"/>
  bool IsDebugEnabled { get; }

  /// <summary>
  /// Checks if this logger is enabled for the <see cref="Level.Info"/> level.
  /// </summary>
  /// <value>
  /// <c>true</c> if this logger is enabled for <see cref="Level.Info"/> events, <c>false</c> otherwise.
  /// </value>
  /// <remarks>
  /// For more information see <see cref="ILog.IsDebugEnabled"/>.
  /// </remarks>
  /// <seealso cref="M:Info(object)"/>
  /// <seealso cref="M:InfoFormat(IFormatProvider, string, object[])"/>
  /// <seealso cref="ILog.IsDebugEnabled"/>
  bool IsInfoEnabled { get; }

  /// <summary>
  /// Checks if this logger is enabled for the <see cref="Level.Warn"/> level.
  /// </summary>
  /// <value>
  /// <c>true</c> if this logger is enabled for <see cref="Level.Warn"/> events, <c>false</c> otherwise.
  /// </value>
  /// <remarks>
  /// For more information see <see cref="ILog.IsDebugEnabled"/>.
  /// </remarks>
  /// <seealso cref="M:Warn(object)"/>
  /// <seealso cref="M:WarnFormat(IFormatProvider, string, object[])"/>
  /// <seealso cref="ILog.IsDebugEnabled"/>
  bool IsWarnEnabled { get; }

  /// <summary>
  /// Checks if this logger is enabled for the <see cref="Level.Error"/> level.
  /// </summary>
  /// <value>
  /// <c>true</c> if this logger is enabled for <see cref="Level.Error"/> events, <c>false</c> otherwise.
  /// </value>
  /// <remarks>
  /// For more information see <see cref="ILog.IsDebugEnabled"/>.
  /// </remarks>
  /// <seealso cref="M:Error(object)"/>
  /// <seealso cref="M:ErrorFormat(IFormatProvider, string, object[])"/>
  /// <seealso cref="ILog.IsDebugEnabled"/>
  bool IsErrorEnabled { get; }

  /// <summary>
  /// Checks if this logger is enabled for the <see cref="Level.Fatal"/> level.
  /// </summary>
  /// <value>
  /// <c>true</c> if this logger is enabled for <see cref="Level.Fatal"/> events, <c>false</c> otherwise.
  /// </value>
  /// <remarks>
  /// For more information see <see cref="ILog.IsDebugEnabled"/>.
  /// </remarks>
  /// <seealso cref="M:Fatal(object)"/>
  /// <seealso cref="M:FatalFormat(IFormatProvider, string, object[])"/>
  /// <seealso cref="ILog.IsDebugEnabled"/>
  bool IsFatalEnabled { get; }
}
