using System.Text;

namespace SwyxTray;

/// <summary>
/// Schlankes Dateiprotokoll unter %LOCALAPPDATA%\SwyxTray\. Bewusst ohne
/// Framework: die App hat kein Fenster, ein Protokoll ist deshalb das einzige
/// Mittel zur Fehlersuche.
/// </summary>
internal static class Log
{
    private const long MaxBytes = 1024 * 1024;
    private static readonly object Gate = new();

    public static bool VerboseEnabled { get; set; }

    public static string Directory { get; } = Path.Combine(
        Environment.GetFolderPath(Environment.SpecialFolder.LocalApplicationData),
        "SwyxTray");

    public static string FilePath { get; } = Path.Combine(Directory, "swyxtray.log");

    public static void Debug(string message)
    {
        if (VerboseEnabled)
        {
            Write("DBG", message);
        }
    }

    public static void Info(string message) => Write("INF", message);

    public static void Error(string message, Exception? ex = null)
        => Write("ERR", ex is null ? message : $"{message} :: {ex}");

    private static void Write(string level, string message)
    {
        var line = $"{DateTime.Now:yyyy-MM-dd HH:mm:ss.fff} [{level}] {message}{Environment.NewLine}";

        lock (Gate)
        {
            try
            {
                System.IO.Directory.CreateDirectory(Directory);
                RollIfTooLarge();
                File.AppendAllText(FilePath, line, Encoding.UTF8);
            }
            catch (Exception ex) when (ex is IOException or UnauthorizedAccessException)
            {
                // Ein fehlschlagendes Protokoll darf die App nicht beenden.
            }
        }
    }

    private static void RollIfTooLarge()
    {
        var info = new FileInfo(FilePath);
        if (!info.Exists || info.Length < MaxBytes)
        {
            return;
        }

        var backup = FilePath + ".1";
        File.Delete(backup);
        File.Move(FilePath, backup);
    }
}