RegexBot/Services/Logging/LoggingService.cs

using Discord;
using System.Reflection;
using System.Text;

namespace RegexBot.Services.Logging;
/// <summary>
/// Implements program-wide logging.
/// </summary>
class LoggingService : Service {
    // NOTE: Service.Log's functionality is implemented here. DO NOT use within this class.
    private readonly string _logBasePath;

    internal LoggingService(RegexbotClient bot) : base(bot) {
        _logBasePath = Path.GetDirectoryName(Assembly.GetEntryAssembly()!.Location)
            + Path.DirectorySeparatorChar + "logs";
        try {
            if (!Directory.Exists(_logBasePath)) Directory.CreateDirectory(_logBasePath);
            Directory.GetFiles(_logBasePath);
        } catch (Exception ex) when (ex is IOException or UnauthorizedAccessException) {
            throw new Exception("Cannot create or access logging directory.");
        }

        bot.DiscordClient.Log += DiscordClient_Log;
    }

    /// <summary>
    /// Discord.Net logging events handled here.
    /// Only events with high importance are stored. Others are just printed to console.
    /// </summary>
    private Task DiscordClient_Log(LogMessage arg) {
        var msg = $"[{Enum.GetName(typeof(LogSeverity), arg.Severity)}] {arg.Message}";
        if (arg.Exception != null) msg += arg.Exception.ToString();

        switch (arg.Message) { // Prevent webhook logs for these 'important' Discord.Net messages
            case "Connecting":
            case "Connected":
            case "Ready":
            case "Disconnecting":
            case "Disconnected":
            case "Resumed previous session":
            case "Failed to resume previous session":
                break;
        }
        DoLog("Discord.Net", msg);

        return Task.CompletedTask;
    }

    // Hooked
    internal void DoLog(string source, string? message) {
        message ??= "(null)";
        var now = DateTimeOffset.Now;
        var output = new StringBuilder();
        var prefix = $"[{now:s}] [{source}] ";
        foreach (var line in message.Split(["\r\n", "\n"], StringSplitOptions.None)) {
            output.Append(prefix).AppendLine(line);
        }
        var outstr = output.ToString();
        Console.Write(outstr);
        var filename = _logBasePath + Path.DirectorySeparatorChar + $"{now:yyyy-MM}.log";
        File.AppendAllText(filename, outstr, Encoding.UTF8);
    }
}