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.

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:

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}";
    }
}