using System.Collections.Concurrent;
using System.Net;
using System.Net.Sockets;
using System.Reflection;
using System.Security.Cryptography;
using System.Text.Json;
using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.AspNetCore.Http;
using Microsoft.AspNetCore.HttpOverrides;
using Microsoft.Extensions.Logging;

namespace MSCO.Server;

/// <summary>
/// Web-Panel: Anmelden, Spielerliste, Kick/Ban/Admin, Banns, Live-Konsole mit Eingabe, Chat,
/// Welt zurücksetzen, Backups, Benutzerverwaltung.
///
/// Port: Standard ist derselbe Port wie der Gameserver - der Server erkennt an den ersten Bytes, ob ein Browser
/// (HTTP) oder das Spiel verbindet, und reicht Browser-Verbindungen an das Panel weiter (das intern nur auf
/// 127.0.0.1 lauscht). Mit PanelPort in server.json läuft es stattdessen auf einem eigenen Port.
///
/// Hinter einem Reverse-Proxy: PanelTrustProxy = true übernimmt X-Forwarded-For/-Proto/-Prefix,
/// PanelBasePath (z.B. "/panel") für den Betrieb unter einem Unterpfad.
/// </summary>
public sealed class AdminPanel
{
    const string CookieName = "msco_panel";
    const string CsrfHeader = "X-MSCO-Panel";
    static readonly TimeSpan SessionLifetime = TimeSpan.FromHours(12);
    static readonly TimeSpan ActionTimeout = TimeSpan.FromSeconds(8);
    const int MaxLoginFailures = 8;
    static readonly TimeSpan LoginWindow = TimeSpan.FromMinutes(5);

    sealed class Session
    {
        public string User;
        public DateTime Expires;
    }

    readonly ServerHost host;   // läuft immer - der Gameserver darunter kann aus sein
    readonly string dataDir;
    ServerConfig config;
    readonly PanelUsers users;
    readonly ConcurrentDictionary<string, Session> sessions = new();
    readonly ConcurrentDictionary<string, List<DateTime>> failures = new();
    // Weitergereichte Verbindungen (gleicher Port): lokaler Port der Weiterleitung -> echte Adresse des Browsers
    readonly ConcurrentDictionary<int, IPAddress> relayed = new();
    WebApplication app;

    /// <summary>Einmal-Code für das erste Konto (null, sobald es einen Benutzer gibt).</summary>
    public string SetupCode { get; private set; }
    /// <summary>Interner Port, wenn das Panel den Spiel-Port mitbenutzt.</summary>
    public int InternalPort { get; private set; }
    public bool SharesGamePort { get; private set; }

    AdminPanel(ServerHost host, ServerConfig config, string dataDir)
    {
        this.host = host;
        this.dataDir = dataDir;
        this.config = config;
        users = new PanelUsers(Path.Combine(dataDir, "panel_users.json"));
    }

    // ---------------------------------------------------------------- Start

    public static AdminPanel Start(ServerHost host, ServerConfig config, string dataDir)
    {
        var panel = new AdminPanel(host, config, dataDir);
        try
        {
            panel.StartWeb();
        }
        catch (Exception e)
        {
            GameServer.Log("Web panel could not start: " + e.Message);
            return null;
        }
        return panel;
    }

    void StartWeb()
    {
        SharesGamePort = config.PanelPort <= 0 || config.PanelPort == config.Port;
        IPAddress bind;
        int port;
        if (SharesGamePort)
        {
            bind = IPAddress.Loopback;
            port = InternalPort = FreeLoopbackPort();
        }
        else
        {
            bind = ParseBind(config.PanelBindAddress);
            port = config.PanelPort;
        }

        var builder = WebApplication.CreateSlimBuilder(new WebApplicationOptions { ContentRootPath = AppContext.BaseDirectory });
        builder.Logging.ClearProviders();
        builder.WebHost.ConfigureKestrel(k =>
        {
            k.Listen(bind, port);
            k.Limits.MaxRequestBodySize = 64 * 1024;
            k.AddServerHeader = false;
        });
        app = builder.Build();

        // Weitergereichte Verbindung: echte Browser-Adresse wiederherstellen (sonst wäre jeder 127.0.0.1)
        app.Use(async (ctx, next) =>
        {
            var remote = ctx.Connection.RemoteIpAddress;
            if (remote != null && IPAddress.IsLoopback(remote) && relayed.TryGetValue(ctx.Connection.RemotePort, out var real))
                ctx.Connection.RemoteIpAddress = real;
            await next();
        });

        if (config.PanelTrustProxy)
        {
            var forwarded = new ForwardedHeadersOptions
            {
                ForwardedHeaders = ForwardedHeaders.XForwardedFor | ForwardedHeaders.XForwardedProto | ForwardedHeaders.XForwardedHost
            };
            forwarded.KnownIPNetworks.Clear(); // jedem Proxy vertrauen (PanelTrustProxy ist eine bewusste Entscheidung)
            forwarded.KnownProxies.Clear();
            app.UseForwardedHeaders(forwarded);
            // Proxy unter Unterpfad (Reverse-Proxy mit X-Forwarded-Prefix)
            app.Use(async (ctx, next) =>
            {
                string prefix = ctx.Request.Headers["X-Forwarded-Prefix"];
                if (!string.IsNullOrEmpty(prefix) && prefix.StartsWith('/')) ctx.Request.PathBase = prefix.TrimEnd('/');
                await next();
            });
        }
        string basePath = (config.PanelBasePath ?? "").Trim().TrimEnd('/');
        if (basePath.Length > 0)
        {
            if (!basePath.StartsWith('/')) basePath = "/" + basePath;
            app.UsePathBase(basePath);
        }

        // Sicherheits-Header
        app.Use(async (ctx, next) =>
        {
            var h = ctx.Response.Headers;
            h["X-Content-Type-Options"] = "nosniff";
            h["X-Frame-Options"] = "DENY";
            h["Referrer-Policy"] = "no-referrer";
            h["Content-Security-Policy"] = "default-src 'self'; img-src 'self' data: https://avatars.steamstatic.com; style-src 'self'; script-src 'self'; frame-ancestors 'none'; base-uri 'none'; form-action 'self'";
            if (ctx.Request.Path.StartsWithSegments("/api")) h["Cache-Control"] = "no-store";
            await next();
        });

        MapFiles();
        MapApi();

        app.StartAsync().GetAwaiter().GetResult();

        if (users.Empty) CreateSetupCode();
        if (SharesGamePort)
            GameServer.Log($"Web panel: http://<server>:{config.Port}/{(basePath.Length > 0 ? basePath.TrimStart('/') + "/" : "")}  (same port as the game)");
        else
            GameServer.Log($"Web panel: http://{(bind.Equals(IPAddress.Any) ? "<server>" : bind.ToString())}:{port}{basePath}/");
    }

    /// <summary>Neu gelesene Einstellungen (der Host liest server.json bei jedem Start neu).</summary>
    public void UpdateConfig(ServerConfig newConfig) => config = newConfig;

    public void Stop()
    {
        try
        {
            using var timeout = new CancellationTokenSource(TimeSpan.FromSeconds(2));
            app?.StopAsync(timeout.Token).GetAwaiter().GetResult();
        }
        catch { }
    }

    void CreateSetupCode()
    {
        const string alphabet = "ABCDEFGHJKLMNPQRSTUVWXYZ23456789";
        var code = new char[10];
        for (int i = 0; i < code.Length; i++) code[i] = alphabet[RandomNumberGenerator.GetInt32(alphabet.Length)];
        SetupCode = new string(code, 0, 5) + "-" + new string(code, 5, 5);
        GameServer.Log("============================================================");
        GameServer.Log("  WEB PANEL SETUP - open the panel in your browser and enter");
        GameServer.Log("  this code to create the owner account:  " + SetupCode);
        GameServer.Log("============================================================");
    }

    /// <summary>Konsolenbefehl "panel": Adresse und (falls noch nötig) den Einrichtungs-Code zeigen.</summary>
    public void PrintInfo()
    {
        GameServer.Log(SharesGamePort ? $"Web panel on the game port {config.Port}" : $"Web panel on port {config.PanelPort}");
        if (SetupCode != null) GameServer.Log("Setup code for the first account: " + SetupCode);
        else GameServer.Log($"{users.All().Count} panel user(s): " + string.Join(", ", users.All().Select(u => $"{u.Name} ({u.Role})")));
    }

    static int FreeLoopbackPort()
    {
        var probe = new TcpListener(IPAddress.Loopback, 0);
        probe.Start();
        int port = ((IPEndPoint)probe.LocalEndpoint).Port;
        probe.Stop();
        return port;
    }

    static IPAddress ParseBind(string address)
    {
        if (string.IsNullOrWhiteSpace(address) || address == "*" || address == "0.0.0.0") return IPAddress.Any;
        if (address == "localhost") return IPAddress.Loopback;
        return IPAddress.TryParse(address, out var ip) ? ip : IPAddress.Any;
    }

    // ---------------------------------------------------------------- Gleicher Port: HTTP erkennen und weiterreichen

    /// <summary>Beginnen die Bytes wie eine HTTP-Anfrage? (Spiel-Pakete beginnen mit einer kleinen Längenangabe.)</summary>
    public static bool LooksLikeHttp(byte[] b, int n)
    {
        if (n < 4) return false;
        for (int i = 0; i < 3; i++)
            if (b[i] < 'A' || b[i] > 'Z') return false;
        return (b[3] >= 'A' && b[3] <= 'Z') || b[3] == ' '; // "GET ", "PUT ", POST, HEAD, DELE, OPTI, PATC ...
    }

    /// <summary>Browser-Verbindung vom Spiel-Port an das intern laufende Panel weiterreichen (in beide Richtungen).</summary>
    public async Task RelayAsync(TcpClient browser)
    {
        var real = (browser.Client.RemoteEndPoint as IPEndPoint)?.Address;
        using var panel = new TcpClient { NoDelay = true };
        int localPort = 0;
        try
        {
            await panel.ConnectAsync(IPAddress.Loopback, InternalPort);
            localPort = ((IPEndPoint)panel.Client.LocalEndPoint).Port;
            if (real != null) relayed[localPort] = real.IsIPv4MappedToIPv6 ? real.MapToIPv4() : real;
            using var a = browser.GetStream();
            using var b = panel.GetStream();
            var up = a.CopyToAsync(b);
            var down = b.CopyToAsync(a);
            await Task.WhenAny(up, down);
        }
        catch { }
        finally
        {
            if (localPort != 0) relayed.TryRemove(localPort, out _);
            try { browser.Close(); } catch { }
        }
    }

    // ---------------------------------------------------------------- Dateien (Oberfläche)

    void MapFiles()
    {
        byte[] html = Resource("panel.index.html"), js = Resource("panel.app.js"), i18n = Resource("panel.i18n.js"), css = Resource("panel.app.css"), logo = Resource("panel.logo.png");
        app.MapGet("/", (HttpContext ctx) =>
        {
            // /panel ohne Schrägstrich -> /panel/ (sonst zeigen die relativen Adressen der Seite ins Leere)
            if (ctx.Request.PathBase.HasValue && !ctx.Request.Path.HasValue)
                return Results.Redirect(ctx.Request.PathBase + "/");
            return Results.Bytes(html, "text/html; charset=utf-8");
        });
        app.MapGet("/app.js", () => Results.Bytes(js, "text/javascript; charset=utf-8"));
        app.MapGet("/i18n.js", () => Results.Bytes(i18n, "text/javascript; charset=utf-8"));
        app.MapGet("/app.css", () => Results.Bytes(css, "text/css; charset=utf-8"));
        if (logo != null) app.MapGet("/logo.png", () => Results.Bytes(logo, "image/png"));
    }

    static byte[] Resource(string name)
    {
        using var s = Assembly.GetExecutingAssembly().GetManifestResourceStream(name);
        if (s == null) return null;
        using var ms = new MemoryStream();
        s.CopyTo(ms);
        return ms.ToArray();
    }

    // ---------------------------------------------------------------- API

    void MapApi()
    {
        // --- Anmeldung
        app.MapGet("/api/session", (HttpContext ctx) =>
        {
            var user = CurrentUser(ctx);
            return Results.Json(new
            {
                needsSetup = users.Empty,
                serverName = config.Name,
                user = user == null ? null : new { name = user.Name, role = user.Role.ToString() }
            });
        });

        app.MapPost("/api/setup", async (HttpContext ctx) =>
        {
            if (!CsrfOk(ctx)) return Forbidden("Missing header");
            if (!users.Empty || SetupCode == null) return Error(400, "The panel is already set up");
            if (RateLimited(ctx)) return Error(429, "Too many attempts - wait a few minutes");
            var body = await Body(ctx);
            string code = Str(body, "code").Trim().ToUpperInvariant();
            if (!CryptographicOperations.FixedTimeEquals(System.Text.Encoding.UTF8.GetBytes(code), System.Text.Encoding.UTF8.GetBytes(SetupCode)))
            {
                RecordFailure(ctx);
                return Error(403, "Wrong setup code (see the server console / docker logs)");
            }
            string name = Str(body, "username").Trim(), password = Str(body, "password");
            string error = users.Add(name, password, PanelRole.Owner);
            if (error != null) return Error(400, error);
            SetupCode = null;
            GameServer.Log($"[panel] Owner account '{name}' created ({Ip(ctx)})");
            StartSession(ctx, name);
            return Results.Json(new { ok = true });
        });

        app.MapPost("/api/login", async (HttpContext ctx) =>
        {
            if (!CsrfOk(ctx)) return Forbidden("Missing header");
            if (RateLimited(ctx)) return Error(429, "Too many failed logins - wait a few minutes");
            var body = await Body(ctx);
            var user = users.Verify(Str(body, "username").Trim(), Str(body, "password"));
            if (user == null)
            {
                RecordFailure(ctx);
                GameServer.Log($"[panel] Failed login for '{Str(body, "username").Trim()}' from {Ip(ctx)}");
                return Error(401, "Wrong username or password");
            }
            failures.TryRemove(Ip(ctx), out _);
            StartSession(ctx, user.Name);
            GameServer.Log($"[panel] {user.Name} logged in ({Ip(ctx)})");
            return Results.Json(new { ok = true });
        });

        app.MapPost("/api/logout", (HttpContext ctx) =>
        {
            if (!CsrfOk(ctx)) return Forbidden("Missing header");
            string token = ctx.Request.Cookies[CookieName];
            if (token != null) sessions.TryRemove(token, out _);
            ctx.Response.Cookies.Delete(CookieName, CookieOptions(ctx));
            return Results.Json(new { ok = true });
        });

        app.MapPost("/api/me/password", async (HttpContext ctx) =>
        {
            var user = Require(ctx, PanelRole.Moderator, out var denied); if (user == null) return denied;
            var body = await Body(ctx);
            if (users.Verify(user.Name, Str(body, "current")) == null) return Error(403, "Current password is wrong");
            string error = users.SetPassword(user.Name, Str(body, "password"));
            if (error != null) return Error(400, error);
            GameServer.Log($"[panel] {user.Name} changed their password");
            return Ok("Password changed");
        });

        // --- Server
        app.MapGet("/api/status", async (HttpContext ctx) =>
        {
            var user = Require(ctx, PanelRole.Moderator, out var denied); if (user == null) return denied;
            return await Run(s => s.PanelStatus(), () => host.OfflineStatus());
        });

        app.MapGet("/api/players", async (HttpContext ctx) =>
        {
            var user = Require(ctx, PanelRole.Moderator, out var denied); if (user == null) return denied;
            bool withAddress = user.Role >= PanelRole.Admin; // IP-Adressen nur für Admins
            return await Run(s => s.PanelPlayers(withAddress), () => Array.Empty<object>());
        });

        app.MapPost("/api/players/{id:int}/{action}", async (HttpContext ctx, int id, string action) =>
        {
            var need = action == "kick" ? PanelRole.Moderator : PanelRole.Admin;
            var user = Require(ctx, need, out var denied); if (user == null) return denied;
            var body = await Body(ctx);
            string by = By(user);
            string reason = Str(body, "reason");
            return action switch
            {
                "kick" => await RunText(s => s.PanelKick(id, false, reason, by)),
                "ban" => await RunText(s => s.PanelKick(id, true, reason, by)),
                "op" => await RunText(s => s.PanelSetAdmin(id, true, by)),
                "deop" => await RunText(s => s.PanelSetAdmin(id, false, by)),
                _ => Error(404, "Unknown action")
            };
        });

        app.MapPost("/api/say", async (HttpContext ctx) =>
        {
            var user = Require(ctx, PanelRole.Moderator, out var denied); if (user == null) return denied;
            var body = await Body(ctx);
            string text = Str(body, "text"), by = By(user);
            return await RunText(s => s.PanelSay(text, by));
        });

        // --- Banns
        app.MapGet("/api/bans", async (HttpContext ctx) =>
        {
            var user = Require(ctx, PanelRole.Moderator, out var denied); if (user == null) return denied;
            return await Run(s => s.PanelBans(), () => config.BannedSteamIds.ToList());
        });

        app.MapPost("/api/bans/add", async (HttpContext ctx) =>
        {
            var user = Require(ctx, PanelRole.Admin, out var denied); if (user == null) return denied;
            var body = await Body(ctx);
            string id = Str(body, "id"), reason = Str(body, "reason"), by = By(user);
            return await RunText(s => s.PanelBanId(id, reason, by), () => OfflineBan(id, true, by));
        });

        app.MapPost("/api/bans/remove", async (HttpContext ctx) =>
        {
            var user = Require(ctx, PanelRole.Admin, out var denied); if (user == null) return denied;
            var body = await Body(ctx);
            string id = Str(body, "id"), by = By(user);
            return await RunText(s => s.PanelUnban(id, by), () => OfflineBan(id, false, by));
        });

        // --- Ingame-Admins (dürfen im Spiel /admin benutzen)
        app.MapGet("/api/admins", async (HttpContext ctx) =>
        {
            var user = Require(ctx, PanelRole.Moderator, out var denied); if (user == null) return denied;
            return await Run(s => s.PanelAdmins(), () => new
            {
                steamVerification = !string.IsNullOrWhiteSpace(config.SteamWebApiKey),
                admins = config.Admins.Select(id => new { steamId = id, name = (string)null, online = false }).ToList()
            });
        });

        app.MapPost("/api/admins/{action}", async (HttpContext ctx, string action) =>
        {
            var user = Require(ctx, PanelRole.Admin, out var denied); if (user == null) return denied;
            var body = await Body(ctx);
            string id = Str(body, "id").Trim(), by = By(user);
            if (id.Length != 17 || !id.All(char.IsDigit)) return Error(400, "Enter a SteamID64 (17 digits)");
            if (action != "add" && action != "remove") return Error(404, "Unknown action");
            bool add = action == "add";
            return await RunText(s => s.RunCommandCaptured((add ? "op " : "deop ") + id, by), () =>
            {
                config.Admins.Remove(id);
                if (add) config.Admins.Add(id);
                try { config.Save(host.ConfigPath); } catch (Exception e) { return "Could not save server.json: " + e.Message; }
                GameServer.Log($"SteamID {id} is {(add ? "now an admin" : "no longer an admin")} ({by})");
                return $"SteamID {id} is {(add ? "now an admin" : "no longer an admin")}";
            });
        });

        // --- Konsole
        app.MapGet("/api/console", (HttpContext ctx) =>
        {
            var user = Require(ctx, PanelRole.Moderator, out var denied); if (user == null) return denied;
            long.TryParse(ctx.Request.Query["after"], out long after);
            var lines = LogBuffer.Since(after, 1000);
            return Results.Json(new
            {
                last = lines.Count > 0 ? lines[^1].Seq : Math.Max(after, 0),
                lines = lines.Select(l => new { seq = l.Seq, time = l.Time, text = l.Text })
            });
        });

        app.MapPost("/api/console", async (HttpContext ctx) =>
        {
            var user = Require(ctx, PanelRole.Admin, out var denied); if (user == null) return denied;
            var body = await Body(ctx);
            string command = Str(body, "command").Trim();
            if (command.Length == 0 || command.Length > 500) return Error(400, "Enter a command");
            string by = By(user);
            if (host.State != HostState.Running || host.Server == null)
            {
                // Server aus: Host-Befehle (start, status, panel ...) - Ausgabe aus dem Log einsammeln
                long from = LogBuffer.LastSeq;
                GameServer.Log($"> {command}   ({by})");
                host.Command(command);
                await Task.Delay(400);
                return Ok(string.Join("\n", LogBuffer.Since(from, 200).Skip(1).Select(l => l.Text)));
            }
            return await RunText(s => s.RunCommandCaptured(command, by));
        });

        // --- Welt / Backups
        app.MapGet("/api/backups", async (HttpContext ctx) =>
        {
            var user = Require(ctx, PanelRole.Admin, out var denied); if (user == null) return denied;
            return await Run(s => s.PanelBackups(), () => SaveStore.BackupDirs(dataDir).Select(d => Path.GetFileName(d)).ToList());
        });

        app.MapPost("/api/world/{action}", async (HttpContext ctx, string action) =>
        {
            var user = Require(ctx, PanelRole.Admin, out var denied); if (user == null) return denied;
            var body = await Body(ctx);
            string name = Str(body, "name"), by = By(user);
            return await RunText(s => s.PanelWorld(action, name, by), () => OfflineWorld(action, name, by));
        });

        // --- Server steuern (Start/Stopp/Neustart)
        app.MapPost("/api/server/{action}", async (HttpContext ctx, string action) =>
        {
            var user = Require(ctx, PanelRole.Admin, out var denied); if (user == null) return denied;
            string by = By(user);
            await Task.CompletedTask;
            return action switch
            {
                "start" => Ok(host.RequestStart(by)),
                "stop" => Ok(host.RequestStop(by)),
                "restart" => Ok(host.RequestRestart(by)),
                _ => Error(404, "Unknown action")
            };
        });

        // --- Einstellungen (server.json)
        app.MapGet("/api/config", async (HttpContext ctx) =>
        {
            var user = Require(ctx, PanelRole.Admin, out var denied); if (user == null) return denied;
            return await Run(s => s.PanelConfig(), () => ConfigEditor.Build(config));
        });

        app.MapPost("/api/config", async (HttpContext ctx) =>
        {
            var user = Require(ctx, PanelRole.Admin, out var denied); if (user == null) return denied;
            var body = await Body(ctx);
            bool owner = user.Role >= PanelRole.Owner;
            string by = By(user);
            return await RunText(s => s.PanelUpdateConfig(body, owner, by), () => ConfigEditor.Apply(config, host.ConfigPath, body, owner, by));
        });

        // --- Spielstand als ZIP
        app.MapGet("/api/save/download", async (HttpContext ctx) =>
        {
            var user = Require(ctx, PanelRole.Admin, out var denied); if (user == null) return denied;
            await Task.CompletedTask;
            if (!SaveStore.HasSave(dataDir)) return Error(404, "There is no save game on the server yet");
            GameServer.Log($"[panel] {user.Name} downloaded the save game");
            return Results.File(SaveStore.ExportZip(dataDir), "application/zip", $"msco-save-{DateTime.Now:yyyyMMdd-HHmmss}.zip");
        });

        app.MapPost("/api/save/upload", async (HttpContext ctx) =>
        {
            var user = Require(ctx, PanelRole.Admin, out var denied); if (user == null) return denied;
            // Größere Grenze nur für den Spielstand
            var sizeFeature = ctx.Features.Get<Microsoft.AspNetCore.Http.Features.IHttpMaxRequestBodySizeFeature>();
            if (sizeFeature != null && !sizeFeature.IsReadOnly) sizeFeature.MaxRequestBodySize = 64L * 1024 * 1024;
            byte[] zip;
            try
            {
                using var ms = new MemoryStream();
                await ctx.Request.Body.CopyToAsync(ms);
                zip = ms.ToArray();
            }
            catch (Exception e) { return Error(400, "Upload failed: " + e.Message); }
            if (zip.Length == 0) return Error(400, "Choose a ZIP, RAR or 7z file");
            string by = By(user);
            var server = host.Server;
            string result;
            if (server == null || host.State != HostState.Running) result = SaveStore.ImportZipOffline(dataDir, zip, by);
            else
            {
                var task = server.Invoke(() => server.ImportSaveZip(zip, by));
                if (await Task.WhenAny(task, Task.Delay(ActionTimeout)) != task) return Error(503, "The server is busy");
                result = await task;
            }
            return result.StartsWith("Save game uploaded") ? Ok(result) : Error(400, result);
        });

        // --- Benutzer (nur Owner)
        app.MapGet("/api/users", (HttpContext ctx) =>
        {
            var user = Require(ctx, PanelRole.Owner, out var denied); if (user == null) return denied;
            return Results.Json(users.All().Select(u => new
            {
                name = u.Name,
                role = u.Role.ToString(),
                created = u.CreatedUtc.ToString("o"),
                lastLogin = u.LastLoginUtc?.ToString("o")
            }));
        });

        app.MapPost("/api/users", async (HttpContext ctx) =>
        {
            var user = Require(ctx, PanelRole.Owner, out var denied); if (user == null) return denied;
            var body = await Body(ctx);
            if (!Enum.TryParse(Str(body, "role"), true, out PanelRole role)) return Error(400, "Unknown role");
            string name = Str(body, "name").Trim();
            string error = users.Add(name, Str(body, "password"), role);
            if (error != null) return Error(400, error);
            GameServer.Log($"[panel] {user.Name} added user '{name}' ({role})");
            return Ok($"User {name} created");
        });

        app.MapPost("/api/users/{name}/{action}", async (HttpContext ctx, string name, string action) =>
        {
            var user = Require(ctx, PanelRole.Owner, out var denied); if (user == null) return denied;
            var body = await Body(ctx);
            string error;
            switch (action)
            {
                case "role":
                    if (!Enum.TryParse(Str(body, "role"), true, out PanelRole role)) return Error(400, "Unknown role");
                    error = users.SetRole(name, role);
                    if (error == null) GameServer.Log($"[panel] {user.Name} changed the role of '{name}' to {role}");
                    break;
                case "password":
                    error = users.SetPassword(name, Str(body, "password"));
                    if (error == null)
                    {
                        EndSessionsOf(name);
                        GameServer.Log($"[panel] {user.Name} reset the password of '{name}'");
                    }
                    break;
                case "delete":
                    if (string.Equals(name, user.Name, StringComparison.OrdinalIgnoreCase)) return Error(400, "You cannot delete yourself");
                    error = users.Remove(name);
                    if (error == null)
                    {
                        EndSessionsOf(name);
                        GameServer.Log($"[panel] {user.Name} deleted user '{name}'");
                    }
                    break;
                default:
                    return Error(404, "Unknown action");
            }
            return error != null ? Error(400, error) : Ok("Done");
        });
    }

    // ---------------------------------------------------------------- Hilfen

    static string By(PanelUsers.User user) => user.Name + " (panel)";

    const string NotRunning = "The game server is not running - start it on the dashboard";

    /// <summary>In der Server-Schleife ausführen; ist der Server aus, whenStopped (oder Fehler 409).</summary>
    async Task<IResult> Run<T>(Func<GameServer, T> func, Func<object> whenStopped = null)
    {
        var server = host.Server;
        if (server == null || host.State != HostState.Running)
            return whenStopped != null ? Results.Json(whenStopped()) : Error(409, NotRunning);
        var task = server.Invoke(() => func(server));
        if (await Task.WhenAny(task, Task.Delay(ActionTimeout)) != task)
            return whenStopped != null ? Results.Json(whenStopped()) : Error(503, "The server is busy or stopping");
        return Results.Json(await task);
    }

    async Task<IResult> RunText(Func<GameServer, string> func, Func<string> whenStopped = null)
    {
        var server = host.Server;
        if (server == null || host.State != HostState.Running)
            return whenStopped != null ? Ok(whenStopped()) : Error(409, NotRunning);
        var task = server.Invoke(() => func(server));
        if (await Task.WhenAny(task, Task.Delay(ActionTimeout)) != task) return Error(503, "The server is busy or stopping");
        return Ok(await task);
    }

    /// <summary>Server aus: Bann direkt in server.json setzen bzw. aufheben.</summary>
    string OfflineBan(string id, bool ban, string by)
    {
        id = (id ?? "").Trim();
        if (ban)
        {
            bool valid = (id.Length == 17 && id.All(char.IsDigit)) || (id.StartsWith("name:") && id.Length > 5 && id.Length < 60);
            if (!valid) return "Enter a SteamID64 (17 digits) or name:playername";
            if (config.BannedSteamIds.Contains(id)) return id + " is already banned";
            config.BannedSteamIds.Add(id);
        }
        else if (!config.BannedSteamIds.Remove(id)) return id + " is not banned";
        try { config.Save(host.ConfigPath); } catch (Exception e) { return "Could not save server.json: " + e.Message; }
        GameServer.Log($"{id} was {(ban ? "banned" : "unbanned")} by {by}");
        return id + (ban ? " is banned" : " is no longer banned");
    }

    /// <summary>Server aus: Spielstand-Aktionen direkt auf den Dateien.</summary>
    string OfflineWorld(string action, string name, string by)
    {
        switch (action)
        {
            case "backup":
                if (!SaveStore.HasSave(dataDir)) return "There is no save game to back up";
                SaveStore.Backup(dataDir);
                GameServer.Log($"Save game backed up by {by}");
                return "Backup created";
            case "reset": return SaveStore.ResetOffline(dataDir, by);
            case "restore": return SaveStore.RestoreOffline(dataDir, name, by);
            case "resetpoint": return SaveStore.SetResetPoint(dataDir) ?? "The current save game is now the reset point";
            case "reloadsave": return "The server is stopped - it loads the save game when you start it";
            case "save": return "The server is stopped - nothing to save";
            default: return "Unknown action";
        }
    }

    static IResult Ok(string message) => Results.Json(new { ok = true, message });
    static IResult Error(int status, string message) => Results.Json(new { error = message }, statusCode: status);
    static IResult Forbidden(string message) => Error(403, message);

    /// <summary>
    /// Nur Anfragen aus der eigenen Oberfläche: sie schicken einen eigenen Header, den eine fremde Webseite ohne
    /// CORS-Freigabe nicht setzen kann (Schutz vor CSRF). Zusätzlich ist das Cookie SameSite=Strict.
    /// </summary>
    static bool CsrfOk(HttpContext ctx) => ctx.Request.Headers[CsrfHeader] == "1";

    PanelUsers.User CurrentUser(HttpContext ctx)
    {
        string token = ctx.Request.Cookies[CookieName];
        if (token == null || !sessions.TryGetValue(token, out var session)) return null;
        if (session.Expires < DateTime.UtcNow) { sessions.TryRemove(token, out _); return null; }
        var user = users.Find(session.User);
        if (user == null) { sessions.TryRemove(token, out _); return null; }
        session.Expires = DateTime.UtcNow + SessionLifetime; // gleitend verlängern
        return user;
    }

    PanelUsers.User Require(HttpContext ctx, PanelRole role, out IResult denied)
    {
        denied = null;
        if (!HttpMethods.IsGet(ctx.Request.Method) && !CsrfOk(ctx)) { denied = Forbidden("Missing header"); return null; }
        var user = CurrentUser(ctx);
        if (user == null) { denied = Error(401, "Please log in"); return null; }
        if (user.Role < role) { denied = Forbidden("Your role (" + user.Role + ") is not allowed to do this"); return null; }
        return user;
    }

    void StartSession(HttpContext ctx, string name)
    {
        string token = Convert.ToBase64String(RandomNumberGenerator.GetBytes(32)).TrimEnd('=').Replace('+', '-').Replace('/', '_');
        sessions[token] = new Session { User = name, Expires = DateTime.UtcNow + SessionLifetime };
        ctx.Response.Cookies.Append(CookieName, token, CookieOptions(ctx));
        // Alte Sitzungen aufräumen
        foreach (var kv in sessions) if (kv.Value.Expires < DateTime.UtcNow) sessions.TryRemove(kv.Key, out _);
    }

    void EndSessionsOf(string name)
    {
        foreach (var kv in sessions)
            if (string.Equals(kv.Value.User, name, StringComparison.OrdinalIgnoreCase)) sessions.TryRemove(kv.Key, out _);
    }

    static CookieOptions CookieOptions(HttpContext ctx) => new()
    {
        HttpOnly = true,
        SameSite = SameSiteMode.Strict,
        Secure = ctx.Request.IsHttps,
        Path = ctx.Request.PathBase.HasValue ? ctx.Request.PathBase.Value : "/",
        MaxAge = SessionLifetime
    };

    static string Ip(HttpContext ctx) => ctx.Connection.RemoteIpAddress?.ToString() ?? "?";

    bool RateLimited(HttpContext ctx)
    {
        if (!failures.TryGetValue(Ip(ctx), out var list)) return false;
        lock (list)
        {
            list.RemoveAll(t => DateTime.UtcNow - t > LoginWindow);
            return list.Count >= MaxLoginFailures;
        }
    }

    void RecordFailure(HttpContext ctx)
    {
        var list = failures.GetOrAdd(Ip(ctx), _ => new List<DateTime>());
        lock (list) list.Add(DateTime.UtcNow);
    }

    static async Task<JsonElement> Body(HttpContext ctx)
    {
        try
        {
            if (ctx.Request.ContentLength is null or 0) return default;
            return await JsonSerializer.DeserializeAsync<JsonElement>(ctx.Request.Body);
        }
        catch { return default; }
    }

    static string Str(JsonElement body, string name) =>
        body.ValueKind == JsonValueKind.Object && body.TryGetProperty(name, out var v) && v.ValueKind == JsonValueKind.String ? v.GetString() ?? "" : "";
}