LogLevel.cs

using System;

namespace CK.Core;

/// <summary>
/// Five standard log levels in increasing order used by <see cref="IActivityMonitor"/>.
/// </summary>
[Flags]
public enum LogLevel
{
    /// <summary>
    /// No logging level.
    /// </summary>
    None = 0,

    /// <summary>
    /// Debug logging level (the most verbose level).
    /// </summary>
    Debug = 1,

    /// <summary>
    /// A trace logging level (quite verbose level).
    /// </summary>
    Trace = 2,

    /// <summary>
    /// An info logging level.
    /// </summary>
    Info = 4,

    /// <summary>
    /// A warn logging level.
    /// </summary>
    Warn = 8,

    /// <summary>
    /// An error logging level: denotes an error for the current activity. 
    /// This error does not necessarily abort the activity.
    /// </summary>
    Error = 16,

    /// <summary>
    /// A fatal error logging level: denotes an error that breaks (aborts)
    /// the current activity. This kind of error may have important side effects
    /// on the system.
    /// </summary>
    Fatal = 32,

    /// <summary>
    /// Mask that covers actual levels to easily ignore <see cref="IsFiltered"/> bit.
    /// </summary>
    Mask = 63,

    /// <summary>
    /// Flag that denotes a log level that has been filtered.
    /// When this flag is not set, the <see cref="IActivityMonitor.UnfilteredOpenGroup"/> or <see cref="IActivityLineEmitter.UnfilteredLog"/> has been 
    /// called directly. When set, the log has typically been emitted through the extension methods that challenge the 
    /// monitor's <see cref="IActivityMonitor.ActualFilter">actual filter</see> and <see cref="ActivityMonitor.DefaultFilter"/> static configuration
    /// and/or the <see cref="ActivityMonitor.Tags"/>.
    /// </summary>
    IsFiltered = 64,

    /// <summary>
    /// Number of bits actually covered by this bit flag.
    /// </summary>
    NumberOfBits = 7
}

/// <summary>
/// Extends <see cref="LogFilter"/>.
/// </summary>
public static class LogLevelExtensions
{
    /// <summary>
    /// Returns 'F', 'E', 'W', 'i', 't' or 'd'. 
    /// </summary>
    /// <param name="l">This log level.</param>
    /// <returns>The char.</returns>
    public static char ToChar( this LogLevel l ) => (l & LogLevel.Mask) switch
    {
        LogLevel.Fatal => 'F',
        LogLevel.Error => 'E',
        LogLevel.Warn => 'W',
        LogLevel.Info => 'i',
        LogLevel.Trace => 't',
        _ => 'd',
    };
}