bepin/BepInEx/Logging/BaseLogger.cs

using System;
using System.IO;
using System.Text;

namespace BepInEx.Logging
{
	/// <summary>
	/// The base implementation of a logging class.
	/// </summary>
	public abstract class BaseLogger : TextWriter
	{
		protected BaseLogger()
		{
			DisplayedLevels = GetDefaultLogLevel();
		}

		/// <summary>
		/// The encoding that the underlying text writer should use. Defaults to UTF-8 BOM.
		/// </summary>
		public override Encoding Encoding { get; } = new UTF8Encoding(true);


		/// <summary>
		/// The handler for a entry logged event.
		/// </summary>
		/// <param name="entry">The text element of the log itself.</param>
		/// <param name="show">Whether or not it should be dislpayed to the user.</param>
		public delegate void EntryLoggedEventHandler(LogLevel level, object entry);

		/// <summary>
		/// The listener event for an entry being logged.
		/// </summary>
		public event EntryLoggedEventHandler EntryLogged;

		/// <summary>
		/// Retrieves the default log level to use for this logger.
		/// </summary>
		/// <returns>The default log level to use.</returns>
		protected virtual LogLevel GetDefaultLogLevel()
		{
			LogLevel lowest;

			try
			{
				lowest = (LogLevel)Enum.Parse(typeof(LogLevel), Config.GetEntry("logger-displayed-levels", nameof(LogLevel.Info), "BepInEx"));
			}
			catch
			{
				return LogLevel.All;
			}

			if (lowest == LogLevel.None)
				return LogLevel.None;

			LogLevel value = lowest;

			foreach (LogLevel e in Enum.GetValues(typeof(LogLevel)))
			{
				if (lowest > e)
					value |= e;
			}

			return value;
		}

		/// <summary>
		/// A filter which is used to specify which log levels are not ignored by the logger.
		/// </summary>
		public LogLevel DisplayedLevels { get; set; }

		private readonly object logLockObj = new object();

		/// <summary>
		/// Logs an entry to the Logger instance.
		/// </summary>
		/// <param name="level">The level of the entry.</param>
		/// <param name="entry">The textual value of the entry.</param>
		public virtual void Log(LogLevel level, object entry)
		{
			if ((DisplayedLevels & level) != LogLevel.None)
			{
				lock (logLockObj)
				{
					EntryLogged?.Invoke(level, entry);
					WriteLine($"[{level.GetHighestLevel()}] {entry}");
				}
			}
		}

		/// <summary>
		/// Logs an entry to the Logger instance, with a <see cref="LogLevel"/> of Message.
		/// </summary>
		/// <param name="entry">The text value of this log entry.</param>
		public virtual void Log(object entry)
		{
			Log(LogLevel.Message, entry);
		}
	}
}