using Serilog;
using Serilog.Core;
using Serilog.Events;

// alias to prevent conflict own Log method
using SerilogLoggingInstance = Serilog.Log;

namespace Common.Logging;

/// <summary>
/// Implements a Logger that uses the Serilog package to create log entries and distributes them into different sinks.
/// Implemented Sinks: File (rolling file), Debug (<see cref="System.Diagnostics.Debug"/>).
/// </summary>
public class SerilogLogger : ILogger
{
    private readonly LoggingLevelSwitch loggingLevelSwitch;

    public event EventHandler<NewLogEntryEventArgs>? NewLogEntry;

    public LogLevel CurrentMinimumLogLevel { get; private set; } = LogLevel.Undefined;

    /// <summary>
    /// Constructor of a Logger that uses the Serilog package to create log entries and distributes them into different sinks.
    /// </summary>
    /// <param name="logFilePath">
    /// path where the logfile shall be created. 
    /// rolling file is created with daily interval. date is automatically added to file name.
    /// Example: "C:/log/log-.txt"
    /// </param>
    /// <param name="logToDebug">
    /// if true the log entries are written to <see cref="System.Diagnostics.Debug"/>. 
    /// Minimum level is ignored for this log entries, therefore every log entry will be logged.
    /// </param>
    public SerilogLogger(string logFilePath, bool logToDebug)
    {
        // create logging level switch and initialized with lowest level
        this.loggingLevelSwitch = new LoggingLevelSwitch() { MinimumLevel = Serilog.Events.LogEventLevel.Verbose };

        // create logger instance
        if (logToDebug)
        {
            SerilogLoggingInstance.Logger = new LoggerConfiguration()
                .WriteTo.Debug()
                .WriteTo.File(logFilePath, 
                    rollingInterval: RollingInterval.Day, 
                    levelSwitch: loggingLevelSwitch,
                    outputTemplate: "{Message:lj}")   // outputTemplate = plain message, formatting is done inside log entry
                .CreateLogger();
        }
        else
        {
            SerilogLoggingInstance.Logger = new LoggerConfiguration()
                .WriteTo.File(logFilePath, 
                    rollingInterval: RollingInterval.Day, 
                    levelSwitch: loggingLevelSwitch,
                    outputTemplate: "{Message:lj}")   // outputTemplate = plain message, formatting is done inside log entry
                .CreateLogger();
        }
    }

    public void Initialize()
    {
        this.Initialize(LogLevel.Trace);
    }

    public void Initialize(LogLevel minimumLogLevel)
    {
        this.SetMinimumLogLevel(minimumLogLevel);
        // Nothing else to do for this logger
    }

    public void SetMinimumLogLevel(LogLevel newMinimumLogLevel)
    {
        this.loggingLevelSwitch.MinimumLevel = this.ConvertGenericToSerilogLogLevel(newMinimumLogLevel);
        this.CurrentMinimumLogLevel = newMinimumLogLevel;
    }

    private LogEventLevel ConvertGenericToSerilogLogLevel(LogLevel newMinimumLogLevel) => newMinimumLogLevel switch
    {
        LogLevel.Undefined => LogEventLevel.Verbose,
        LogLevel.Trace => LogEventLevel.Verbose,
        LogLevel.Debug => LogEventLevel.Debug,
        LogLevel.Info => LogEventLevel.Information,
        LogLevel.Warn => LogEventLevel.Warning,
        LogLevel.Error => LogEventLevel.Error,
        _ => throw new NotImplementedException($"'{nameof(ConvertGenericToSerilogLogLevel)}()' does not contain an entry for {nameof(LogLevel)} {newMinimumLogLevel}"),
    };

    public void StopLogging()
    {
        SerilogLoggingInstance.CloseAndFlush();
    }


    #region Logging methods
    public void Log(LogEntry logEntry)
    {
        var serilogEventLevel = this.ConvertGenericToSerilogLogLevel(logEntry.LogLevel);

        // formatting is done inside logEntry.ToString() method => therefore log plain message text with right category
        switch (serilogEventLevel)
        {
            case LogEventLevel.Verbose:
                SerilogLoggingInstance.Verbose(logEntry.ToString());
                break;

            case LogEventLevel.Debug:
                SerilogLoggingInstance.Debug(logEntry.ToString());
                break;

            case LogEventLevel.Information:
                SerilogLoggingInstance.Information(logEntry.ToString());
                break;

            case LogEventLevel.Warning:
                SerilogLoggingInstance.Warning(logEntry.ToString());
                break;

            case LogEventLevel.Error:
                SerilogLoggingInstance.Error(logEntry.ToString());
                break;

            case LogEventLevel.Fatal:
                SerilogLoggingInstance.Error(logEntry.ToString());
                break;

            default:
                throw new NotImplementedException($"'{nameof(Log)}()' does not contain an implementation for {nameof(LogEventLevel)} {serilogEventLevel}.");
        }

        // Raise event (only if the log is wanted due to the configured log level)
        if (logEntry.LogLevel <= this.CurrentMinimumLogLevel)
        {
            this.NewLogEntry?.Invoke(this, new NewLogEntryEventArgs(logEntry));
        }
    }

    public void LogTrace(string message, string category = "")
    {
        this.Log(new LogEntry { Category = category, LogLevel = LogLevel.Trace, Message = message });
    }

    public void LogDebug(string message, string category = "")
    {
        this.Log(new LogEntry { Category = category, LogLevel = LogLevel.Debug, Message = message });
    }

    public void LogInfo(string message, string category = "")
    {
        this.Log(new LogEntry { Category = category, LogLevel = LogLevel.Info, Message = message });
    }

    public void LogWarn(string message, string category = "")
    {
        this.Log(new LogEntry { Category = category, LogLevel = LogLevel.Warn, Message = message });
    }

    public void LogError(string message, string category = "")
    {
        this.Log(new LogEntry { Category = category, LogLevel = LogLevel.Error, Message = message });
    }

    public void LogException(Exception exception, string category = "")
    {
        this.Log(new LogEntry { Category = category, LogLevel = LogLevel.Error, Exception = exception });
    }

    public void LogException(Exception exception, string message, string category = "")
    {
        this.Log(
            new LogEntry
            {
                Category = category,
                LogLevel = LogLevel.Error,
                Message = message,
                Exception = exception
            });
    }
    #endregion

}