LLamaSharp/docs/More/log.md

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# The Logger in LLamaSharp
LLamaSharp supports customized logger because it could be used in many kinds of applications, like Winform/WPF, WebAPI and Blazor, so that the preference of logger varies.
## Define customized logger
What you need to do is to implement the `ILogger` interface.
```cs
public interface ILLamaLogger
{
public enum LogLevel
{
Info,
Debug,
Warning,
Error
}
void Log(string source, string message, LogLevel level);
}
```
The `source` specifies where the log message is from, which could be a function, a class, etc..
The `message` is the log message itself.
The `level` is the level of the information in the log. As shown above, there're four levels, which are `info`, `debug`, `warning` and `error` respectively.
The following is a simple example of the logger implementation:
```cs
public sealed class LLamaDefaultLogger : ILLamaLogger
{
private static readonly Lazy<LLamaDefaultLogger> _instance = new Lazy<LLamaDefaultLogger>(() => new LLamaDefaultLogger());
private bool _toConsole = true;
private bool _toFile = false;
private FileStream? _fileStream = null;
private StreamWriter _fileWriter = null;
public static LLamaDefaultLogger Default => _instance.Value;
private LLamaDefaultLogger()
{
}
public LLamaDefaultLogger EnableConsole()
{
_toConsole = true;
return this;
}
public LLamaDefaultLogger DisableConsole()
{
_toConsole = false;
return this;
}
public LLamaDefaultLogger EnableFile(string filename, FileMode mode = FileMode.Append)
{
_fileStream = new FileStream(filename, mode, FileAccess.Write);
_fileWriter = new StreamWriter(_fileStream);
_toFile = true;
return this;
}
public LLamaDefaultLogger DisableFile(string filename)
{
if (_fileWriter is not null)
{
_fileWriter.Close();
_fileWriter = null;
}
if (_fileStream is not null)
{
_fileStream.Close();
_fileStream = null;
}
_toFile = false;
return this;
}
public void Log(string source, string message, LogLevel level)
{
if (level == LogLevel.Info)
{
Info(message);
}
else if (level == LogLevel.Debug)
{
}
else if (level == LogLevel.Warning)
{
Warn(message);
}
else if (level == LogLevel.Error)
{
Error(message);
}
}
public void Info(string message)
{
message = MessageFormat("info", message);
if (_toConsole)
{
Console.ForegroundColor = ConsoleColor.White;
Console.WriteLine(message);
Console.ResetColor();
}
if (_toFile)
{
Debug.Assert(_fileStream is not null);
Debug.Assert(_fileWriter is not null);
_fileWriter.WriteLine(message);
}
}
public void Warn(string message)
{
message = MessageFormat("warn", message);
if (_toConsole)
{
Console.ForegroundColor = ConsoleColor.Yellow;
Console.WriteLine(message);
Console.ResetColor();
}
if (_toFile)
{
Debug.Assert(_fileStream is not null);
Debug.Assert(_fileWriter is not null);
_fileWriter.WriteLine(message);
}
}
public void Error(string message)
{
message = MessageFormat("error", message);
if (_toConsole)
{
Console.ForegroundColor = ConsoleColor.Red;
Console.WriteLine(message);
Console.ResetColor();
}
if (_toFile)
{
Debug.Assert(_fileStream is not null);
Debug.Assert(_fileWriter is not null);
_fileWriter.WriteLine(message);
}
}
private string MessageFormat(string level, string message)
{
DateTime now = DateTime.Now;
string formattedDate = now.ToString("yyyy.MM.dd HH:mm:ss");
return $"[{formattedDate}][{level}]: {message}";
}
}
```