using System.Net;
using System.Net.Sockets;
using BSO.Net;

namespace BSO.Server;

/// <summary>
/// Dedizierter Server: nimmt Spieler an (Hello -> Welcome), merkt sich den letzten Zustand jedes Spielers und reicht
/// ihn an alle anderen weiter. Laeuft in einer einzigen Schleife (Tick) - alle Verbindungen werden dort abgefragt,
/// es braucht keine Sperren.
/// </summary>
public class GameServer
{
    public const string Version = "0.3.0";
    static readonly TimeSpan HelloTimeout = TimeSpan.FromSeconds(10);
    static readonly TimeSpan SilenceTimeout = TimeSpan.FromSeconds(30); // Mod pingt alle 2 s

    class Client
    {
        public int Id;
        public string Name;
        public string Address;
        public Connection Conn;
        public bool Welcomed;
        public DateTime Connected, LastMessage;
        public PlayerState State;
        public bool HasState;
        public string AccountId; // aus dem Spiel-Ticket (null mit --no-auth)
    }

    readonly TcpListener listener;
    readonly Dictionary<int, Client> clients = new();
    int nextId = 1;

    public string Name { get; }
    public int MaxPlayers { get; }
    public TestBot Bot { get; private set; }
    /// <summary>Fuer den Heartbeat (anderer Thread) - wird in Tick aktualisiert.</summary>
    public int PlayerCount => playerCount;
    volatile int playerCount;

    /// <summary>Spiel-Tickets pruefen (Konto der BSO-Website)? Aus mit --no-auth (LAN, Tests).</summary>
    public bool RequireAccount { get; set; } = true;
    public MasterClient Master { get; set; }

    public GameServer(int port, string name, int maxPlayers)
    {
        Name = name;
        MaxPlayers = maxPlayers;
        // IPv4 und IPv6 (die Website prueft die Erreichbarkeit ueber die Adresse, von der der Heartbeat kam - das kann IPv6 sein)
        listener = new TcpListener(IPAddress.IPv6Any, port);
        listener.Server.DualMode = true;
        listener.Start();
        Log($"BSO Server {Version} (Protokoll {Protocol.Version}) auf Port {port} - \"{name}\", max. {maxPlayers} Spieler");
    }

    public static void Log(string line) => Console.WriteLine(DateTime.Now.ToString("HH:mm:ss") + "  " + line);

    public void Tick()
    {
        while (listener.Pending())
        {
            TcpClient tcp = listener.AcceptTcpClient();
            var c = new Client
            {
                Id = nextId++,
                Address = (tcp.Client.RemoteEndPoint as IPEndPoint)?.Address.ToString() ?? "?",
                Conn = new Connection(tcp),
                Connected = DateTime.UtcNow,
                LastMessage = DateTime.UtcNow
            };
            clients[c.Id] = c;
        }

        DateTime now = DateTime.UtcNow;
        foreach (Client c in clients.Values.ToList())
        {
            foreach (Message m in c.Conn.Poll())
            {
                c.LastMessage = now;
                try { Handle(c, m); }
                catch (Exception e) { c.Conn.Close("Ungueltige Nachricht " + m.Type + ": " + e.Message); }
            }
            if (!c.Welcomed && now - c.Connected > HelloTimeout) c.Conn.Close("Kein Hello");
            if (now - c.LastMessage > SilenceTimeout) c.Conn.Close("Zeitueberschreitung");
            if (c.Conn.IsClosed) Remove(c);
        }

        playerCount = Players().Count();
        if (Bot != null && Bot.Tick(Players().Where(p => p.HasState).Select(p => p.State)))
            Broadcast(MsgType.PlayerState, StatePayload(Bot.Id, Bot.State), except: 0);
    }

    void Handle(Client c, Message m)
    {
        BinaryReader r = m.Reader();
        switch (m.Type)
        {
            case MsgType.Info:
                c.Conn.Send(MsgType.InfoReply, Wire.Build(w =>
                {
                    w.Write(Name);
                    w.Write(Version);
                    w.Write(Players().Count());
                    w.Write(MaxPlayers);
                }));
                break;

            case MsgType.Hello:
                if (c.Welcomed) return;
                int protocol = r.ReadInt32();
                string modVersion = r.ReadString();
                string name = Clean(r.ReadString(), c.Id);
                if (protocol != Protocol.Version)
                {
                    Reject(c, $"Versionen passen nicht: Server Protokoll {Protocol.Version}, Mod {modVersion} hat Protokoll {protocol}");
                    return;
                }
                // Ab Protokoll 2: Spiel-Ticket des Launchers - der Name kommt dann aus dem Konto, nicht vom Spieler
                string ticketText = r.ReadString();
                if (RequireAccount)
                {
                    if (Master?.TicketKey == null)
                    {
                        Reject(c, "Der Server kann gerade keine BSO-Konten pruefen (Website nicht erreichbar)");
                        return;
                    }
                    Ticket ticket = Ticket.Verify(ticketText, Master.TicketKey, out string ticketError);
                    if (ticket == null)
                    {
                        Reject(c, ticketError);
                        return;
                    }
                    if (Players().Any(p => p.AccountId == ticket.AccountId))
                    {
                        Reject(c, $"Das Konto {ticket.Username} ist schon auf diesem Server");
                        return;
                    }
                    c.AccountId = ticket.AccountId;
                    name = Clean(ticket.Username, c.Id);
                }
                if (Players().Count() >= MaxPlayers)
                {
                    Reject(c, $"Server ist voll ({MaxPlayers} Spieler)");
                    return;
                }
                c.Name = name;
                c.Welcomed = true;
                var others = Others(c.Id).ToList();
                c.Conn.Send(MsgType.Welcome, Wire.Build(w =>
                {
                    w.Write(c.Id);
                    w.Write(Name);
                    w.Write(others.Count);
                    foreach ((int id, string n, _, _) in others) { w.Write(id); w.Write(n); }
                }));
                // Letzten Stand der anderen gleich mitschicken, damit sie nicht erst beim naechsten Paket auftauchen
                foreach ((int id, _, bool has, PlayerState s) in others)
                    if (has) c.Conn.Send(MsgType.PlayerState, StatePayload(id, s));
                Broadcast(MsgType.PlayerJoined, Wire.Build(w => { w.Write(c.Id); w.Write(c.Name); }), except: c.Id);
                Log($"{c.Name} (#{c.Id}, {c.Address}, Mod {modVersion}) ist beigetreten - {Players().Count()} Spieler");
                break;

            case MsgType.PlayerState:
                if (!c.Welcomed) return;
                c.State = PlayerState.Read(r);
                c.HasState = true;
                Broadcast(MsgType.PlayerState, StatePayload(c.Id, c.State), except: c.Id);
                break;

            case MsgType.Ping:
                c.Conn.Send(MsgType.Pong, m.Payload);
                break;
        }
    }

    void Reject(Client c, string reason)
    {
        Log($"{c.Address} abgelehnt: {reason}");
        c.Conn.Send(MsgType.Reject, Wire.Build(w => w.Write(reason)));
        c.Conn.Close(reason);
    }

    void Remove(Client c)
    {
        clients.Remove(c.Id);
        if (!c.Welcomed) return;
        Broadcast(MsgType.PlayerLeft, Wire.Build(w => w.Write(c.Id)), except: c.Id);
        Log($"{c.Name} (#{c.Id}) ist gegangen: {c.Conn.CloseReason} - {Players().Count()} Spieler");
    }

    IEnumerable<Client> Players() => clients.Values.Where(c => c.Welcomed && !c.Conn.IsClosed);

    /// <summary>Alle anderen Spieler inkl. Testbot: (ID, Name, hat Zustand, Zustand).</summary>
    IEnumerable<(int, string, bool, PlayerState)> Others(int self)
    {
        foreach (Client p in Players())
            if (p.Id != self) yield return (p.Id, p.Name, p.HasState, p.State);
        if (Bot != null) yield return (Bot.Id, Bot.Name, Bot.HasState, Bot.State);
    }

    void Broadcast(MsgType type, byte[] payload, int except)
    {
        foreach (Client p in Players())
            if (p.Id != except) p.Conn.Send(type, payload);
    }

    static byte[] StatePayload(int id, PlayerState s) => Wire.Build(w => { w.Write(id); s.Write(w); });

    static string Clean(string name, int id)
    {
        name = new string((name ?? "").Where(ch => !char.IsControl(ch)).ToArray()).Trim();
        if (name.Length > 24) name = name.Substring(0, 24);
        return name.Length > 0 ? name : "Spieler" + id;
    }

    // ---------------------------------------------------------------------------------------------------------------
    // Konsole

    public void Command(string line)
    {
        string[] parts = line.Trim().Split(' ', 2, StringSplitOptions.RemoveEmptyEntries);
        if (parts.Length == 0) return;
        switch (parts[0].ToLowerInvariant())
        {
            case "help":
                Log("Befehle: status, bot, kick <id> [grund], stop");
                break;
            case "status":
            case "players":
                Log($"{Players().Count()}/{MaxPlayers} Spieler" + (Bot != null ? " + Testbot" : ""));
                foreach (Client p in Players())
                    Log($"  #{p.Id} {p.Name} ({p.Address}) " + (p.HasState ? $"{p.State.Mode} bei {p.State.X / 100:0} / {p.State.Y / 100:0} m, {p.State.Speed * 0.036f:0} km/h" : "noch keine Position"));
                break;
            case "bot":
                if (Bot == null) AddBot();
                else
                {
                    Broadcast(MsgType.PlayerLeft, Wire.Build(w => w.Write(Bot.Id)), except: 0);
                    Bot = null;
                    Log("Testbot entfernt");
                }
                break;
            case "kick":
                string[] args = parts.Length > 1 ? parts[1].Split(' ', 2) : Array.Empty<string>();
                if (args.Length > 0 && int.TryParse(args[0], out int kickId) && clients.TryGetValue(kickId, out Client k))
                {
                    string reason = args.Length > 1 ? args[1] : "Vom Server entfernt";
                    Reject(k, reason);
                }
                else Log("kick <id> [grund] - IDs siehe status");
                break;
            default:
                Log("Unbekannter Befehl - help");
                break;
        }
    }

    public void AddBot()
    {
        Bot = new TestBot(nextId++);
        Broadcast(MsgType.PlayerJoined, Wire.Build(w => { w.Write(Bot.Id); w.Write(Bot.Name); }), except: 0);
        Log($"Testbot #{Bot.Id} da - faehrt Kreise um den ersten Spieler, der im Spiel ist");
    }

    public void Stop()
    {
        foreach (Client c in clients.Values) c.Conn.Close("Server beendet");
        listener.Stop();
    }
}