using EC.Util.Common;
using System.Collections.Concurrent;
using System.Net;
using System.Net.Sockets;
using System.Runtime.InteropServices;
using System.Text;

namespace JiLinApp.Docking.VibrateAlarm;

public class AsyncTcpServer : IDisposable
{
    #region Fields

    private TcpListener Listener { get; set; }

    private ConcurrentDictionary<string, TcpClientState> Clients { get; }

    #region Properties

    /// <summary>
    /// 监听的IP地址
    /// </summary>
    public IPAddress Address { get; private set; }

    /// <summary>
    /// 监听的端口
    /// </summary>
    public int Port { get; private set; }

    /// <summary>
    /// 通信使用的编码
    /// </summary>
    public Encoding Encoding { get; set; }

    public bool Disposed { get; private set; }

    #endregion Properties

    #endregion Fields

    #region Ctors

    /// <summary>
    /// 异步TCP服务器
    /// </summary>
    /// <param name="port">监听的端口</param>
    public AsyncTcpServer(int port) : this(IPAddress.Any, port)
    {
    }

    /// <summary>
    /// 异步TCP服务器
    /// </summary>
    /// <param name="ipep">监听的终结点</param>
    public AsyncTcpServer(IPEndPoint ipep) : this(ipep.Address, ipep.Port)
    {
    }

    /// <summary>
    /// 异步TCP服务器
    /// </summary>
    /// <param name="address">监听的IP地址</param>
    /// <param name="port">监听的端口</param>
    public AsyncTcpServer(IPAddress address, int port)
    {
        Address = address;
        Port = port;
        Encoding = Encoding.Default;
        Listener = new(address, port);
        Clients = new();
        if (RuntimeInformation.IsOSPlatform(OSPlatform.Windows)) Listener.AllowNatTraversal(true);
    }

    ~AsyncTcpServer()
    {
        Stop();
    }

    #endregion Ctors

    #region Server

    /// <summary>
    /// 启动服务器
    /// </summary>
    /// <returns>异步TCP服务器</returns>
    public void Start()
    {
        Start(30);
    }

    /// <summary>
    /// 启动服务器
    /// </summary>
    /// <param name="backlog">服务器所允许的挂起连接序列的最大长度</param>
    /// <returns>异步TCP服务器</returns>
    public void Start(int backlog)
    {
        if (IsRunning()) return;
        Listener.Start(backlog);
        AcceptTcpClient(Listener);
    }

    /// <summary>
    /// 停止服务器
    /// </summary>
    /// <returns>异步TCP服务器</returns>
    public void Stop()
    {
        if (!IsRunning()) return;
        try
        {
            Listener.Stop();
        }
        finally
        {
            foreach (var client in Clients.Values)
            {
                client.Client.Client.Disconnect(false);
            }
            Clients.Clear();
        }
    }

    public bool IsRunning()
    {
        return Listener != null && Listener.Server.IsBound;
    }

    public ICollection<TcpClientState> GetAllClient()
    {
        return Clients.Values;
    }

    #endregion Server

    #region Events

    /// <summary>
    /// 与客户端的连接已建立事件
    /// </summary>
    public event EventHandler<TcpClientConnectedEventArgs>? ClientConnected;

    /// <summary>
    /// 与客户端的连接已断开事件
    /// </summary>
    public event EventHandler<TcpClientDisconnectedEventArgs>? ClientDisconnected;

    /// <summary>
    /// 接收到数据报文事件
    /// </summary>
    public event EventHandler<TcpDatagramReceivedEventArgs<byte[]>>? DatagramReceived;

    private void RaiseClientConnected(string clientAddr, TcpClientState clientState)
    {
        if (string.IsNullOrEmpty(clientAddr) || clientAddr.Equals(":")) return;
        Clients.AddOrUpdate(clientAddr, clientState, (n, o) => { return clientState; });
        ClientConnected?.Invoke(this, new TcpClientConnectedEventArgs(clientState.Client));
    }

    private void RaiseClientDisconnected(string clientAddr, TcpClient client)
    {
        if (string.IsNullOrEmpty(clientAddr) || clientAddr.Equals(":")) return;
        client.Client.Disconnect(false);
        if (Clients.TryRemove(clientAddr, out _))
        {
            ClientDisconnected?.Invoke(this, new TcpClientDisconnectedEventArgs(client));
        }
    }

    private void RaiseDatagramReceived(TcpClientState sender, byte[] datagram)
    {
        DatagramReceived?.Invoke(this, new TcpDatagramReceivedEventArgs<byte[]>(sender, datagram));
    }

    #endregion Events

    #region Receive

    private void AcceptTcpClient(TcpListener listener)
    {
        listener.BeginAcceptTcpClient(HandleTcpClientAccepted, listener);
    }

    private void HandleTcpClientAccepted(IAsyncResult ar)
    {
        if (!IsRunning()) return;
        if (ar.AsyncState is not TcpListener listener) return;

        TcpClient? client;
        try
        {
            client = listener.EndAcceptTcpClient(ar);
            if (client == null || !client.Connected)
            {
                client?.Client.Disconnect(false);
                return;
            }
        }
        catch (Exception)
        {
            return;
        }

        // add client connection to cache
        string clientAddr = client.ClientAddr();
        byte[] buffer = new byte[client.ReceiveBufferSize];
        TcpClientState clientState = new(client, buffer);
        RaiseClientConnected(clientAddr, clientState);

        // begin to read data
        ReadBuffer(clientState);

        // keep listening to accept next connection
        AcceptTcpClient(listener);
    }

    private void ReadBuffer(TcpClientState clientState)
    {
        try
        {
            NetworkStream stream = clientState.GetStream;
            if (clientState.IsRead) return;
            lock (clientState.IsReadLock)
            {
                if (clientState.IsRead) return;
                clientState.IsRead = true;
                stream.BeginRead(clientState.Buffer, 0, clientState.Buffer.Length, HandleDatagramReceived, clientState);
            }
        }
        catch (IOException e)
        {
            LogUnit.Error(e);
            return;
        }
        catch (Exception e)
        {
            LogUnit.Error(e);
            string clientAddr = clientState.Client.ClientAddr();
            RaiseClientDisconnected(clientAddr, clientState.Client);
        }
    }

    private void HandleDatagramReceived(IAsyncResult ar)
    {
        if (!IsRunning()) return;
        if (ar.AsyncState is not TcpClientState clientState) return;

        int readNum;
        string clientAddr = clientState.Client.ClientAddr();
        try
        {
            NetworkStream networkStream = clientState.GetStream;
            // if the remote host has shutdown its connection, read will immediately return with zero bytes.
            readNum = networkStream.EndRead(ar);
            if (readNum == 0)
            {
                RaiseClientDisconnected(clientAddr, clientState.Client);
                return;
            }
        }
        catch (Exception)
        {
            RaiseClientDisconnected(clientAddr, clientState.Client);
            return;
        }

        // received byte and trigger event notification
        byte[] receivedBytes = new byte[readNum];
        Buffer.BlockCopy(clientState.Buffer, 0, receivedBytes, 0, readNum);
        RaiseDatagramReceived(clientState, receivedBytes);

        lock (clientState.IsReadLock)
        {
            clientState.IsRead = false;
        }
        // continue listening for tcp datagram packets
        ReadBuffer(clientState);
    }

    #endregion Receive

    #region Send

    /// <summary>
    /// 发送报文至指定的客户端
    /// </summary>
    /// <param name="client">客户端</param>
    /// <param name="datagram">报文</param>
    public void Send(TcpClient client, byte[] datagram)
    {
        if (!IsRunning()) return;
        if (client == null || datagram == null) return;
        try
        {
            NetworkStream stream = client.GetStream();
            stream.Write(datagram, 0, datagram.Length);
        }
        catch (Exception)
        {
            string clientAddr = client.ClientAddr();
            RaiseClientDisconnected(clientAddr, client);
        }
    }

    /// <summary>
    /// 发送报文至指定的客户端
    /// </summary>
    /// <param name="client">客户端</param>
    /// <param name="datagram">报文</param>
    public void Send(TcpClient client, string datagram)
    {
        Send(client, Encoding.GetBytes(datagram));
    }

    /// <summary>
    /// 发送报文至所有客户端
    /// </summary>
    /// <param name="datagram">报文</param>
    public void SendToAll(byte[] datagram)
    {
        if (!IsRunning()) return;
        foreach (var client in Clients.Values)
        {
            Send(client.Client, datagram);
        }
    }

    /// <summary>
    /// 发送报文至所有客户端
    /// </summary>
    /// <param name="datagram">报文</param>
    public void SendToAll(string datagram)
    {
        if (!IsRunning()) return;
        SendToAll(Encoding.GetBytes(datagram));
    }

    /// <summary>
    /// 发送报文至指定的客户端
    /// </summary>
    /// <param name="client">客户端</param>
    /// <param name="datagram">报文</param>
    public bool SendAsync(TcpClient client, byte[] datagram)
    {
        if (!IsRunning()) return false;
        if (client == null || datagram == null) return false;
        try
        {
            NetworkStream stream = client.GetStream();
            IAsyncResult result = stream.BeginWrite(datagram, 0, datagram.Length, HandleDatagramWritten, client);
            return result.IsCompleted;
        }
        catch (Exception)
        {
            string clientAddr = client.ClientAddr();
            RaiseClientDisconnected(clientAddr, client);
        }
        return false;
    }

    /// <summary>
    /// 发送报文至指定的客户端
    /// </summary>
    /// <param name="client">客户端</param>
    /// <param name="datagram">报文</param>
    public bool SendAsync(TcpClient client, string datagram)
    {
        return SendAsync(client, Encoding.GetBytes(datagram));
    }

    /// <summary>
    /// 发送报文至所有客户端
    /// </summary>
    /// <param name="datagram">报文</param>
    public void SendToAllAsync(byte[] datagram)
    {
        if (!IsRunning()) return;
        foreach (var client in Clients.Values)
        {
            SendAsync(client.Client, datagram);
        }
    }

    /// <summary>
    /// 发送报文至所有客户端
    /// </summary>
    /// <param name="datagram">报文</param>
    public void SendToAllAsync(string datagram)
    {
        if (!IsRunning()) return;
        SendToAllAsync(Encoding.GetBytes(datagram));
    }

    private void HandleDatagramWritten(IAsyncResult ar)
    {
        if (ar.AsyncState is not TcpClient client) return;
        try
        {
            client.GetStream().EndWrite(ar);
        }
        catch (Exception)
        {
            string clientAddr = client.ClientAddr();
            RaiseClientDisconnected(clientAddr, client);
        }
    }

    #endregion Send

    #region IDisposable Members

    /// <summary>
    /// Performs application-defined tasks associated with freeing, releasing, or resetting unmanaged resources.
    /// </summary>
    public void Dispose()
    {
        Dispose(true);
        GC.SuppressFinalize(this);
    }

    /// <summary>
    /// Releases unmanaged and - optionally - managed resources
    /// </summary>
    /// <param name="disposing"><c>true</c> to release both managed and unmanaged resources;
    /// <c>false</c> to release only unmanaged resources.</param>
    protected virtual void Dispose(bool disposing)
    {
        if (!Disposed)
        {
            if (disposing) Stop();
            Disposed = true;
        }
    }

    #endregion IDisposable Members
}