using System.Text;
using System.Text.RegularExpressions;

namespace CVRManager.Services;

public static class MultiInstance
{
    const int KeepLogs = 7;

    static readonly Regex SingleInstanceLine = new(@"^single-instance[^\r\n]*(\r?\n|$)", RegexOptions.Multiline | RegexOptions.Compiled);

    public static void Prepare(string gameDir, Action<string> log)
    {
        RemoveSingleInstanceFlag(gameDir, log);
        PruneMelonLoaderLogs(gameDir, log);
    }

    static void RemoveSingleInstanceFlag(string gameDir, Action<string> log)
    {
        var boot = Path.Combine(gameDir, "ChilloutVR_Data", "boot.config");
        if (!File.Exists(boot)) return;
        var text = File.ReadAllText(boot);
        var cleaned = SingleInstanceLine.Replace(text, "");
        if (cleaned == text) return;
        File.WriteAllText(boot, cleaned, new UTF8Encoding(false));
        log("Removed 'single-instance' from boot.config so more than one instance can run.");
    }

    static void PruneMelonLoaderLogs(string gameDir, Action<string> log)
    {
        var logs = Path.Combine(gameDir, "MelonLoader", "Logs");
        if (!Directory.Exists(logs)) return;
        var files = new DirectoryInfo(logs).GetFiles("*.log").OrderBy(f => f.LastWriteTimeUtc).ToList();
        var excess = files.Count - KeepLogs;
        var removed = 0;
        foreach (var f in files)
        {
            if (removed >= excess) break;
            try
            {
                f.Delete();
                removed++;
            }
            catch (Exception e) when (e is IOException or UnauthorizedAccessException) { }
        }
        if (removed > 0) log($"Removed {removed} old MelonLoader log(s) so a second instance does not trip MelonLoader's log cleanup.");
    }
}