using System.Diagnostics;
using System.IO.Compression;
using System.Reflection;
using System.Runtime.Loader;
using System.Text.Json;
using System.Text.RegularExpressions;

namespace MSCO.Server;

/// <summary>
/// Server-Updates aus dem Git-Repository (git.mbm.wtf). Prüft regelmäßig, ob auf "main" eine neuere Version
/// (&lt;Version&gt; in MSCO.Server.csproj) liegt. Installieren im Panel: Quellcode laden, mit dem .NET SDK bauen
/// (dotnet publish) und nach DATA/app/current legen, dann neu starten. Beim Start lädt das Programm von dort die neuere
/// Version (siehe RunInstalled) - so klappt es auch in Docker, wo /app zum Image gehört. Ein neueres Image
/// (docker compose up --build) gewinnt wieder gegen ein älteres installiertes Update.
/// </summary>
public sealed class Updater
{
    /// <summary>Exit-Code "neu starten für das Update" - Docker (restart: unless-stopped) und systemd starten neu.</summary>
    public const int RestartExitCode = 75;
    const int MaxStartAttempts = 3;
    static readonly TimeSpan CheckInterval = TimeSpan.FromHours(6);
    static readonly TimeSpan BuildTimeout = TimeSpan.FromMinutes(15);
    const int MaxLogLines = 400;

    /// <summary>Quelle der Updates (für Forks/Tests per MSCO_UPDATE_SOURCE änderbar).</summary>
    public static string Source => (Environment.GetEnvironmentVariable("MSCO_UPDATE_SOURCE") ?? "https://git.mbm.wtf/MrMaho/MSCO-Dedicated-Server").TrimEnd('/');
    public static string Branch => Environment.GetEnvironmentVariable("MSCO_UPDATE_BRANCH") ?? "main";
    static string Api
    {
        get
        {
            var u = new Uri(Source);
            return $"{u.Scheme}://{u.Authority}/api/v1/repos{u.AbsolutePath.TrimEnd('/')}";
        }
    }

    static readonly HttpClient Http = CreateHttp();

    static HttpClient CreateHttp()
    {
        var http = new HttpClient { Timeout = TimeSpan.FromSeconds(30) };
        http.DefaultRequestHeaders.UserAgent.ParseAdd("MSCO-Server/" + CurrentVersion);
        return http;
    }

    // ---------------------------------------------------------------- eigene Version

    static string Informational =>
        typeof(Updater).Assembly.GetCustomAttribute<AssemblyInformationalVersionAttribute>()?.InformationalVersion ?? "0.0.0";

    /// <summary>Version dieses Programms (aus MSCO.Server.csproj), z.B. "2.9.0".</summary>
    public static string CurrentVersion => Informational.Split('+')[0];

    /// <summary>Git-Commit dieses Builds (nur bei per Update gebauten Versionen bekannt).</summary>
    public static string CurrentCommit
    {
        get
        {
            int plus = Informational.IndexOf('+');
            return plus < 0 ? null : Informational[(plus + 1)..];
        }
    }

    public static bool IsNewer(string candidate, string than) =>
        Version.TryParse(candidate, out var a) && Version.TryParse(than, out var b) && a > b;

    /// <summary>&lt;Version&gt; aus einer .csproj-Datei.</summary>
    public static string ParseCsprojVersion(string csproj)
    {
        var m = Regex.Match(csproj ?? "", @"<Version>\s*([0-9][0-9.]*)\s*</Version>");
        return m.Success ? m.Groups[1].Value : null;
    }

    /// <summary>Mod-Version (Protokoll) aus GameServer.cs.</summary>
    public static string ParseModVersion(string source)
    {
        var m = Regex.Match(source ?? "", @"ModVersion\s*=\s*""([^""]+)""");
        return m.Success ? m.Groups[1].Value : null;
    }

    // ---------------------------------------------------------------- Zustand fürs Panel

    public enum Step { Idle, Downloading, Building, Installing, Restarting, Failed }

    public sealed class Commit
    {
        public string Sha, Title, Date;
    }

    sealed class Latest
    {
        public string Version, Commit, Date, Message, ModVersion;
        public List<Commit> Changes = new();
    }

    readonly ServerHost host;
    readonly string dataDir;
    readonly object gate = new();
    readonly List<string> log = new();
    Latest latest;
    DateTime? lastCheckUtc;
    string checkError;
    Step step = Step.Idle;
    int progress;
    string message, error, target, startedBy;
    DateTime stepSinceUtc = DateTime.UtcNow;
    bool notified;
    (bool ok, string reason)? sdk;

    public Updater(ServerHost host, string dataDir)
    {
        this.host = host;
        this.dataDir = dataDir;
    }

    string AppDir => Path.Combine(dataDir, "app");
    string WorkDir => Path.Combine(dataDir, "update");

    /// <summary>Hintergrund: kurz nach dem Start und dann alle 6 Stunden prüfen; neu installierte Version als gut markieren.</summary>
    public void StartBackground()
    {
        _ = Task.Run(async () =>
        {
            await Task.Delay(TimeSpan.FromSeconds(60));
            MarkHealthy(); // eine Minute ohne Absturz: das installierte Update läuft
            while (true)
            {
                try { await CheckAsync(); } catch { }
                await Task.Delay(CheckInterval);
            }
        });
    }

    bool firstCheckStarted;

    public object Status()
    {
        // Noch nie geprüft (gerade erst gestartet): jetzt im Hintergrund prüfen, damit das Panel den Punkt bald zeigt
        if (lastCheckUtc == null && !firstCheckStarted)
        {
            firstCheckStarted = true;
            _ = Task.Run(async () => { try { await CheckAsync(); } catch { } });
        }
        lock (gate)
        {
            var sdkInfo = sdk;
            return new
            {
                current = CurrentVersion,
                currentCommit = CurrentCommit,
                modVersion = GameServer.ModVersion,
                source = Source,
                branch = Branch,
                latest = latest?.Version,
                latestCommit = latest?.Commit,
                latestDate = latest?.Date,
                latestMessage = latest?.Message,
                latestModVersion = latest?.ModVersion,
                available = latest != null && IsNewer(latest.Version, CurrentVersion),
                changes = latest?.Changes.Select(c => new { sha = c.Sha, title = c.Title, date = c.Date }),
                lastCheck = lastCheckUtc?.ToString("o"),
                checkError,
                canInstall = sdkInfo?.ok,
                cannotInstall = sdkInfo is { ok: false } ? sdkInfo.Value.reason : null,
                supervised = Supervised,
                step = step.ToString().ToLowerInvariant(),
                progress,
                message,
                error,
                target,
                startedBy,
                stepSince = stepSinceUtc.ToString("o"),
                log = log.ToArray()
            };
        }
    }

    public bool Busy
    {
        get { lock (gate) return step is Step.Downloading or Step.Building or Step.Installing or Step.Restarting; }
    }

    void SetStep(Step s, int percent, string text)
    {
        lock (gate)
        {
            if (s != step) stepSinceUtc = DateTime.UtcNow;
            step = s;
            progress = percent;
            message = text;
        }
        AddLog("== " + text);
    }

    void SetProgress(int percent, string text = null)
    {
        lock (gate)
        {
            progress = Math.Max(progress, Math.Clamp(percent, 0, 100));
            if (text != null) message = text;
        }
    }

    void AddLog(string line)
    {
        lock (gate)
        {
            log.Add(line);
            if (log.Count > MaxLogLines) log.RemoveRange(0, log.Count - MaxLogLines);
        }
    }

    // ---------------------------------------------------------------- Prüfen

    /// <summary>Neueste Version auf dem Branch abfragen.</summary>
    public async Task CheckAsync()
    {
        CheckSdk();
        try
        {
            using var branchDoc = JsonDocument.Parse(await Http.GetStringAsync($"{Api}/branches/{Branch}"));
            var commit = branchDoc.RootElement.GetProperty("commit");
            string sha = commit.GetProperty("id").GetString();
            string msg = commit.TryGetProperty("message", out var m) ? m.GetString() : "";
            string date = commit.TryGetProperty("timestamp", out var t) ? t.GetString() : null;

            string version = ParseCsprojVersion(await Http.GetStringAsync($"{Source}/raw/commit/{sha}/MSCO.Server.csproj"))
                             ?? throw new Exception("No <Version> in MSCO.Server.csproj");
            string modVersion = null;
            try { modVersion = ParseModVersion(await Http.GetStringAsync($"{Source}/raw/commit/{sha}/GameServer.cs")); } catch { }

            var found = new Latest
            {
                Version = version, Commit = sha, Date = date, ModVersion = modVersion,
                Message = (msg ?? "").Split('\n')[0].Trim()
            };
            if (IsNewer(version, CurrentVersion))
            {
                try { found.Changes = await ChangesAsync(sha); } catch { }
            }

            bool newlyAvailable;
            lock (gate)
            {
                newlyAvailable = IsNewer(version, CurrentVersion) && (latest == null || latest.Version != version || !notified);
                latest = found;
                lastCheckUtc = DateTime.UtcNow;
                checkError = null;
                if (newlyAvailable) notified = true;
            }
            if (newlyAvailable)
                GameServer.Log($"Update available: MSCO server {version} (you have {CurrentVersion}) - install it in the web panel (Update)" +
                               (modVersion != null && modVersion != GameServer.ModVersion ? $". Players then need MSCO mod {modVersion}." : ""));
        }
        catch (Exception e)
        {
            lock (gate)
            {
                lastCheckUtc = DateTime.UtcNow;
                checkError = "Could not check for updates: " + Short(e);
            }
        }
    }

    /// <summary>Commits seit der eigenen Version (bzw. die letzten, wenn der eigene Commit unbekannt ist).</summary>
    async Task<List<Commit>> ChangesAsync(string sha)
    {
        using var doc = JsonDocument.Parse(await Http.GetStringAsync(
            $"{Api}/commits?sha={sha}&limit=30&stat=false&verification=false&files=false"));
        var list = new List<Commit>();
        string own = CurrentCommit;
        foreach (var c in doc.RootElement.EnumerateArray())
        {
            string id = c.GetProperty("sha").GetString();
            if (own != null && id.StartsWith(own, StringComparison.OrdinalIgnoreCase)) break;
            var inner = c.GetProperty("commit");
            string text = inner.GetProperty("message").GetString() ?? "";
            string date = inner.TryGetProperty("author", out var a) && a.TryGetProperty("date", out var d) ? d.GetString() : null;
            list.Add(new Commit { Sha = id[..Math.Min(8, id.Length)], Title = text.Split('\n')[0].Trim(), Date = date });
            if (list.Count >= (own != null ? 30 : 10)) break;
        }
        return list;
    }

    /// <summary>Ist ein .NET SDK zum Bauen da? (Docker-Image ab 2.9 enthält es.)</summary>
    void CheckSdk()
    {
        if (sdk != null) return;
        try
        {
            var psi = new ProcessStartInfo(DotnetPath(), "--list-sdks") { RedirectStandardOutput = true, RedirectStandardError = true, UseShellExecute = false };
            using var p = Process.Start(psi);
            string output = p.StandardOutput.ReadToEnd();
            p.WaitForExit(15000);
            int need = Environment.Version.Major;
            bool ok = output.Split('\n').Any(l => int.TryParse(l.Split('.')[0].Trim(), out int major) && major >= need);
            lock (gate) sdk = ok ? (true, null) : (false, $"No .NET {need} SDK found - it is needed to build the update. " +
                "With Docker: pull the new version once (git pull && docker compose up -d --build), its image contains the SDK.");
        }
        catch (Exception e)
        {
            lock (gate) sdk = (false, "The dotnet command was not found (" + Short(e) + ") - install the .NET SDK to update from the panel.");
        }
    }

    static string DotnetPath()
    {
        string self = Environment.ProcessPath;
        string name = Path.GetFileNameWithoutExtension(self ?? "");
        return name.Equals("dotnet", StringComparison.OrdinalIgnoreCase) ? self : "dotnet";
    }

    // ---------------------------------------------------------------- Installieren

    /// <summary>Update im Hintergrund laden, bauen, installieren und neu starten. null = gestartet, sonst Fehlertext.</summary>
    public string Install(string by)
    {
        lock (gate)
        {
            if (step is Step.Downloading or Step.Building or Step.Installing or Step.Restarting) return "An update is already running";
            if (latest == null || !IsNewer(latest.Version, CurrentVersion)) return "No update available - check again first";
            if (sdk is { ok: false }) return sdk.Value.reason;
            log.Clear();
            error = null;
            target = latest.Version;
            startedBy = by;
            step = Step.Downloading;
            progress = 0;
            stepSinceUtc = DateTime.UtcNow;
        }
        GameServer.Log($"Server update to {target} started by {by}");
        _ = Task.Run(InstallAsync);
        return null;
    }

    async Task InstallAsync()
    {
        try
        {
            // 1) Quellcode des neuesten Commits laden
            SetStep(Step.Downloading, 2, "Checking the newest version");
            await CheckAsync();
            Latest want;
            lock (gate) want = latest;
            if (want == null || !IsNewer(want.Version, CurrentVersion)) throw new Exception(checkError ?? "No update available anymore");
            lock (gate) target = want.Version;

            Directory.CreateDirectory(WorkDir);
            string zip = Path.Combine(WorkDir, "source.zip"), src = Path.Combine(WorkDir, "src");
            SetStep(Step.Downloading, 5, $"Downloading MSCO server {want.Version} ({want.Commit[..8]})");
            await DownloadAsync($"{Source}/archive/{want.Commit}.zip", zip);
            if (Directory.Exists(src)) Directory.Delete(src, true);
            ZipFile.ExtractToDirectory(zip, src);
            string csproj = Directory.GetFiles(src, "MSCO.Server.csproj", SearchOption.AllDirectories)
                                .OrderBy(p => p.Length).FirstOrDefault()
                            ?? throw new Exception("MSCO.Server.csproj not found in the download");
            SetProgress(25, "Download complete");

            // 2) Bauen
            string build = Path.Combine(AppDir, "build");
            if (Directory.Exists(build)) Directory.Delete(build, true);
            SetStep(Step.Building, 27, "Building (dotnet publish) - this takes a minute");
            await BuildAsync(csproj, build, want.Commit);
            string dll = Path.Combine(build, "MSCO.Server.dll");
            if (!File.Exists(dll)) throw new Exception("The build did not produce MSCO.Server.dll");

            // 3) Installieren: build -> current (die bisherige bleibt als previous)
            SetStep(Step.Installing, 92, "Installing");
            WriteInfo(build, new InstallInfo { Version = want.Version, Commit = want.Commit, InstalledUtc = DateTime.UtcNow, By = startedBy });
            string current = Path.Combine(AppDir, "current"), previous = Path.Combine(AppDir, "previous");
            if (Directory.Exists(previous)) Directory.Delete(previous, true);
            if (Directory.Exists(current)) Directory.Move(current, previous);
            Directory.Move(build, current);
            try { Directory.Delete(src, true); File.Delete(zip); } catch { }
            AddLog("Installed to " + current);

            // 4) Neu starten - die Spieler verbinden sich danach automatisch wieder
            SetStep(Step.Restarting, 96, $"Restarting with version {want.Version}");
            var server = host.Server;
            if (server != null && host.State == HostState.Running)
            {
                // im Server-Thread: Spieler zählen und vorwarnen
                var warn = server.Invoke(() => server.JoinedCount > 0
                    && server.PanelSay("Server update - restarting in 5 seconds, you reconnect automatically", "Server") != null);
                if (await Task.WhenAny(warn, Task.Delay(3000)) == warn && warn.Result) await Task.Delay(5000);
            }
            await Task.Delay(1500); // Panel: "Neustart" noch anzeigen lassen
            GameServer.Log($"Update {want.Version} installed - restarting");
            host.ExitForUpdate();
        }
        catch (Exception e)
        {
            lock (gate)
            {
                step = Step.Failed;
                error = Short(e);
                message = "Update failed";
                stepSinceUtc = DateTime.UtcNow;
            }
            AddLog("FAILED: " + Short(e));
            GameServer.Log("Server update failed: " + Short(e) + " - the server keeps running the old version");
        }
    }

    async Task DownloadAsync(string url, string file)
    {
        using var res = await Http.GetAsync(url, HttpCompletionOption.ResponseHeadersRead);
        res.EnsureSuccessStatusCode();
        long? total = res.Content.Headers.ContentLength;
        await using var input = await res.Content.ReadAsStreamAsync();
        await using var output = File.Create(file);
        var buffer = new byte[81920];
        long done = 0;
        int read;
        while ((read = await input.ReadAsync(buffer)) > 0)
        {
            await output.WriteAsync(buffer.AsMemory(0, read));
            done += read;
            string mb = (done / 1048576.0).ToString("0.0", System.Globalization.CultureInfo.InvariantCulture);
            if (total > 0) SetProgress(5 + (int)(18 * done / total.Value), $"Downloading … {mb} MB");
            else SetProgress(Math.Min(22, 5 + (int)(done / 100_000)), $"Downloading … {mb} MB");
        }
        AddLog($"Downloaded {done / 1024} KB");
    }

    async Task BuildAsync(string csproj, string output, string commit)
    {
        var psi = new ProcessStartInfo(DotnetPath())
        {
            UseShellExecute = false,
            RedirectStandardOutput = true,
            RedirectStandardError = true,
            WorkingDirectory = Path.GetDirectoryName(csproj)
        };
        foreach (string a in new[] { "publish", csproj, "-c", "Release", "-o", output, "--nologo", "--disable-build-servers",
                     "-p:SourceRevisionId=" + commit, "-p:UseAppHost=" + (OperatingSystem.IsWindows() ? "true" : "false") })
            psi.ArgumentList.Add(a);
        // Alles Schreibbare in den Datenordner (in Docker ist HOME nur /tmp)
        psi.Environment["DOTNET_CLI_HOME"] = Path.Combine(WorkDir, "home");
        psi.Environment["NUGET_PACKAGES"] = Path.Combine(WorkDir, "nuget");
        psi.Environment["DOTNET_CLI_TELEMETRY_OPTOUT"] = "1";
        psi.Environment["DOTNET_NOLOGO"] = "1";
        psi.Environment["DOTNET_SKIP_FIRST_TIME_EXPERIENCE"] = "1";
        psi.Environment["MSBUILDDISABLENODEREUSE"] = "1";

        using var p = new Process { StartInfo = psi };
        void OnLine(string line)
        {
            if (string.IsNullOrWhiteSpace(line)) return;
            AddLog(line.TrimEnd());
            if (line.Contains("Restored ") || line.Contains("All projects are up-to-date")) SetProgress(45, "Building - packages restored");
            else if (line.Contains(" -> ") && line.Contains(".dll")) SetProgress(80, "Building - compiled");
            else if (line.Contains(" -> ")) SetProgress(90, "Building - published");
        }
        p.OutputDataReceived += (_, e) => { if (e.Data != null) OnLine(e.Data); };
        p.ErrorDataReceived += (_, e) => { if (e.Data != null) OnLine(e.Data); };
        p.Start();
        p.BeginOutputReadLine();
        p.BeginErrorReadLine();

        // Fortschritt langsam weiterlaufen lassen, solange das Bauen dauert
        var started = DateTime.UtcNow;
        while (!p.HasExited)
        {
            await Task.Delay(1000);
            if (DateTime.UtcNow - started > BuildTimeout)
            {
                try { p.Kill(true); } catch { }
                throw new Exception("The build took longer than " + BuildTimeout.TotalMinutes + " minutes");
            }
            lock (gate) if (progress < 88) progress++;
        }
        p.WaitForExit();
        if (p.ExitCode != 0)
        {
            string lastError;
            lock (gate) lastError = log.LastOrDefault(l => l.Contains("error", StringComparison.OrdinalIgnoreCase)) ?? "see the log";
            throw new Exception($"The build failed (exit code {p.ExitCode}): {lastError}");
        }
        SetProgress(91, "Build complete");
    }

    static string Short(Exception e)
    {
        while (e.InnerException != null && e is AggregateException or TargetInvocationException) e = e.InnerException;
        return e.Message;
    }

    // ---------------------------------------------------------------- Neu starten

    /// <summary>Läuft das Programm unter Docker/systemd (die starten nach dem Beenden neu)?</summary>
    public static bool Supervised =>
        Environment.GetEnvironmentVariable("DOTNET_RUNNING_IN_CONTAINER") == "true"
        || Environment.GetEnvironmentVariable("INVOCATION_ID") != null // systemd
        || Environment.GetEnvironmentVariable("MSCO_SUPERVISED") == "1";

    /// <summary>Nach dem Beenden für ein Update: ohne Docker/systemd startet sich das Programm selbst neu.</summary>
    public static void Relaunch(string[] args)
    {
        if (Supervised)
        {
            GameServer.Log("Exiting for the update - Docker/systemd starts the server again");
            return;
        }
        try
        {
            string self = Environment.ProcessPath;
            var all = new List<string>();
            if (Path.GetFileNameWithoutExtension(self).Equals("dotnet", StringComparison.OrdinalIgnoreCase))
                all.Add(Environment.GetCommandLineArgs()[0]); // die gestartete MSCO.Server.dll
            all.AddRange(args);
            var psi = new ProcessStartInfo(self)
            {
                Arguments = string.Join(" ", all.Select(Quote)),
                WorkingDirectory = Environment.CurrentDirectory,
                UseShellExecute = OperatingSystem.IsWindows() // Windows: neues Konsolenfenster
            };
            Process.Start(psi);
            GameServer.Log("Started the updated server");
        }
        catch (Exception e)
        {
            GameServer.Log("Could not restart automatically (" + e.Message + ") - please start the server again");
        }
    }

    static string Quote(string a) => a.Length > 0 && a.IndexOfAny(new[] { ' ', '"', '\t' }) < 0 ? a : "\"" + a.Replace("\"", "\\\"") + "\"";

    // ---------------------------------------------------------------- installierte Version starten

    sealed class InstallInfo
    {
        public string Version { get; set; }
        public string Commit { get; set; }
        public DateTime InstalledUtc { get; set; }
        public string By { get; set; }
        public int Attempts { get; set; }
        public bool Verified { get; set; }
    }

    static InstallInfo ReadInfo(string dir)
    {
        try { return JsonSerializer.Deserialize<InstallInfo>(File.ReadAllText(Path.Combine(dir, "msco-update.json"))); }
        catch { return null; }
    }

    static void WriteInfo(string dir, InstallInfo info) =>
        File.WriteAllText(Path.Combine(dir, "msco-update.json"), JsonSerializer.Serialize(info, new JsonSerializerOptions { WriteIndented = true }));

    /// <summary>Läuft gerade eine installierte Update-Version? Dann nach einer Minute als funktionierend merken.</summary>
    static void MarkHealthy()
    {
        string dir = Environment.GetEnvironmentVariable("MSCO_UPDATE_DIR");
        if (dir == null) return;
        var info = ReadInfo(dir);
        if (info == null || info.Verified) return;
        info.Verified = true;
        info.Attempts = 0;
        try { WriteInfo(dir, info); } catch { }
    }

    /// <summary>
    /// Ganz am Anfang von Program: liegt in DATA/app/current eine neuere Version, diese statt der eigenen ausführen
    /// (im selben Prozess, eigener AssemblyLoadContext - Signale, Konsole und Docker bleiben gleich). Gibt den Exit-Code
    /// zurück oder null, wenn die eigene Version laufen soll.
    /// </summary>
    public static int? RunInstalled(string[] args, string dataDir)
    {
        if (Environment.GetEnvironmentVariable("MSCO_UPDATE_DIR") != null) return null; // wir SIND die installierte Version
        if (Environment.GetEnvironmentVariable("MSCO_NO_UPDATES") == "1") return null;
        string dir = Path.Combine(dataDir, "app", "current");
        var info = ReadInfo(dir);
        if (info == null) return null;
        string dll = Path.Combine(dir, "MSCO.Server.dll");
        if (!File.Exists(dll)) return null;
        if (!IsNewer(info.Version, CurrentVersion))
        {
            // Das Programm selbst ist gleich neu oder neuer (z.B. neues Docker-Image) - altes Update aufräumen
            Console.WriteLine($"Installed update {info.Version} is not newer than this version ({CurrentVersion}) - removing it");
            try { Directory.Delete(Path.Combine(dataDir, "app"), true); } catch { }
            return null;
        }
        if (!info.Verified && info.Attempts >= MaxStartAttempts)
        {
            Console.WriteLine($"The installed update {info.Version} failed to start {info.Attempts} times - running the built-in version {CurrentVersion}");
            try
            {
                string failed = Path.Combine(dataDir, "app", "failed");
                if (Directory.Exists(failed)) Directory.Delete(failed, true);
                Directory.Move(dir, failed);
            }
            catch { }
            return null;
        }
        if (!info.Verified)
        {
            info.Attempts++;
            try { WriteInfo(dir, info); } catch { }
        }

        MethodInfo entry;
        try
        {
            var context = new UpdateLoadContext(dll);
            entry = context.LoadFromAssemblyPath(dll).EntryPoint ?? throw new Exception("no entry point");
        }
        catch (Exception e)
        {
            Console.WriteLine($"Could not load the installed update {info.Version}: {e.Message} - running the built-in version {CurrentVersion}");
            return null;
        }
        Console.WriteLine($"Starting installed update {info.Version} (built-in version {CurrentVersion})");
        Environment.SetEnvironmentVariable("MSCO_UPDATE_DIR", dir);
        try
        {
            object result = entry.Invoke(null, entry.GetParameters().Length == 0 ? null : new object[] { args });
            if (result is Task<int> task) return task.GetAwaiter().GetResult();
            if (result is Task plain) { plain.GetAwaiter().GetResult(); return 0; }
            return result is int code ? code : 0;
        }
        catch (TargetInvocationException e) when (e.InnerException != null)
        {
            System.Runtime.ExceptionServices.ExceptionDispatchInfo.Capture(e.InnerException).Throw();
            throw;
        }
    }

    /// <summary>Lädt die installierte Version samt ihren Abhängigkeiten (z.B. SharpCompress) aus ihrem Ordner.</summary>
    sealed class UpdateLoadContext : AssemblyLoadContext
    {
        readonly AssemblyDependencyResolver resolver;

        public UpdateLoadContext(string mainAssembly) : base("msco-update") => resolver = new AssemblyDependencyResolver(mainAssembly);

        protected override Assembly Load(AssemblyName name)
        {
            string path = resolver.ResolveAssemblyToPath(name);
            return path != null ? LoadFromAssemblyPath(path) : null; // Framework (ASP.NET ...) aus dem Standard-Kontext
        }

        protected override IntPtr LoadUnmanagedDll(string name)
        {
            string path = resolver.ResolveUnmanagedDllToPath(name);
            return path != null ? LoadUnmanagedDllFromPath(path) : IntPtr.Zero;
        }
    }
}