dragon-iso/src/Dragon-ISO.App/StartupTrace.cs

using System.IO;

namespace DragonISO.App;

/// <summary>
/// Bare-metal startup tracer that opens, appends, and closes a file on
/// every call. Used to capture what's happening BEFORE Serilog comes up
/// (and to capture failures that would prevent Serilog from coming up at
/// all). Failures here are swallowed — we never want diagnostics to crash
/// the very thing we're trying to diagnose.
///
/// File lives at <c>%LOCALAPPDATA%\Dragon-ISO\startup-trace.log</c>. Grows
/// without rotation; expected to be tiny since each launch writes ~20
/// lines. Acceptable cost for catching launch-time regressions.
/// </summary>
internal static class StartupTrace
{
    private static readonly object _gate = new();

    public static void Write(string message)
    {
        try
        {
            var dir = Path.Combine(
                Environment.GetFolderPath(Environment.SpecialFolder.LocalApplicationData),
                "Dragon-ISO");
            Directory.CreateDirectory(dir);
            var path = Path.Combine(dir, "startup-trace.log");
            var line = $"[{DateTimeOffset.Now:yyyy-MM-dd HH:mm:ss.fff}] [PID {Environment.ProcessId}] {message}{Environment.NewLine}";
            lock (_gate)
            {
                File.AppendAllText(path, line);
            }
        }
        catch
        {
            // Diagnostics must NEVER crash startup.
        }
    }
}