using System;
using System.Collections.Generic;
using System.Net.Sockets;
using UnityEngine;
using UnityEngine.Assertions;

public enum HeaderCode
{
    Invalid = 0,
    Heartbeat = 1,
    JoinGame = 100,
}

public struct Header
{
    public HeaderCode code;
    public int size;

    public void SetData(byte[] bytes)
    {
        Debug.Assert(bytes.Length == GetSize(), $"Header size is invalid! {bytes.Length}");

        code = (HeaderCode)BitConverter.ToInt32(bytes, 0);
        size = BitConverter.ToInt32(bytes, sizeof(HeaderCode));
    }

    public byte[] GetData()
    {
        byte[] bytes = new byte[GetSize()];
        BitConverter.GetBytes((int)code).CopyTo(bytes, 0);
        BitConverter.GetBytes(size).CopyTo(bytes, sizeof(HeaderCode));

        return bytes;
    }

    public static int GetSize() => sizeof(HeaderCode) + sizeof(int);
}

public struct Body
{
    public byte[] data;
}

public class Packet
{
    public Header header;
    public Body body;

    public byte[] GetData()
    {
        byte[] headerData = header.GetData();
        byte[] data = new byte[headerData.Length + header.size];

        headerData.CopyTo(data, 0);
        body.data.CopyTo(data, headerData.Length);

        return data;
    }
}

public class Session
{
    Queue<byte> penddingBuffer = new Queue<byte>();

    Header currentHeader;
    Body currentBody;

    public Header CurrentHeader => currentHeader;
    public Body CurrentBody => currentBody;

    public Session()
    {
        ClearHeader();
    }

    public void PenddingData(byte[] data)
    {
        for (int i = 0; i < data.Length; i++)
        {
            penddingBuffer.Enqueue(data[i]);
        }
    }

    public bool TryParseHeader()
    {
        int headerSize = Header.GetSize();

        if (currentHeader.code == HeaderCode.Invalid && penddingBuffer.Count >= headerSize)
        {
            byte[] headerData = new byte[headerSize];
            for (int i = 0; i < headerSize; i++)
                headerData[i] = penddingBuffer.Dequeue();

            currentHeader.SetData(headerData);
        }

        return currentHeader.code != HeaderCode.Invalid;
    }

    public bool TryParseBody()
    {
        if (currentHeader.code != HeaderCode.Invalid && penddingBuffer.Count >= currentHeader.size)
        {
            byte[] bodyData = new byte[currentHeader.size];
            for (int i = 0; i < currentHeader.size; i++)
                bodyData[i] = penddingBuffer.Dequeue();

            currentBody.data = bodyData;
            return true;
        }

        return false;
    }

    public void ClearHeader()
    {
        currentHeader.code = HeaderCode.Invalid;
        currentHeader.size = 0;
    }
}

public abstract class TcpServerClient : MonoBehaviour
{
    [SerializeField] string host = "127.0.0.1";
    [SerializeField] int port = 123;
    [SerializeField] int bufferSize = 1024 * 8; // 8KB

    TcpClient client;
    NetworkStream stream;
    byte[] reciveBuffer;
    Session session;

    Queue<Packet> recievedPacket = new Queue<Packet>();

    public bool IsConnected => client != null && client.Connected;

    private void OnApplicationQuit()
    {
        if(client != null && client.Connected)
            client.Close();
    }

    private void Start()
    {
        Invoke(nameof(test), 5);
    }

    private void test()
    {
        //temp code
        Header header = new Header
        {
            code = HeaderCode.JoinGame,
            size = UserState.GetSize(),
        };

        Body body = new Body();
        Vector3 position = new Vector3(0, 0, 0);
        byte[] data = new byte[sizeof(float) * 3];
        BitConverter.GetBytes(position.x).CopyTo(data, 0);
        BitConverter.GetBytes(position.y).CopyTo(data, sizeof(float));
        BitConverter.GetBytes(position.z).CopyTo(data, sizeof(float) * 2);
        body.data = data;

        Send(new Packet { header = header, body = body });
    }

    void Update()
    {
        while (recievedPacket.Count > 0)
        {
            OnDataReceived(recievedPacket.Dequeue());
        }
    }

    public void Connect()
    {
        if(IsConnected)
        {
            Logger.LogWarning("Already connected to server!");
            return;
        }

        client = new TcpClient
        {
            ReceiveBufferSize = bufferSize,
            SendBufferSize = bufferSize,
        };

        session = new Session();

        client.BeginConnect(host, port, ConnectCallback, null);
    }

    public async void Send(Packet packet)
    {
        if (!IsConnected)
        {
            Logger.LogError("Failed to send packet! Not connected to server!");
            return;
        }

        var dataBytes = packet.GetData();

        try
        {
            await stream.WriteAsync(dataBytes, 0, dataBytes.Length);
        }
        catch (Exception e)
        {
            Logger.LogError(e);
        }
    }

    private void ConnectCallback(IAsyncResult ar)
    {
        client.EndConnect(ar);

        if(!client.Connected)
        {
            Debug.LogError("Failed to connect server!");
            return;
        }

        Logger.Log("Connected to server!");

        stream = client.GetStream();
        reciveBuffer = new byte[bufferSize];

        stream.BeginRead(reciveBuffer, 0, bufferSize, ReadCallback, null);
    }

    private void ReadCallback(IAsyncResult ar)
    {
        try
        {
            int read = stream.EndRead(ar);

            if (read <= 0)
                return;

            byte[] buffer = new byte[read];
            Array.Copy(reciveBuffer, buffer, read);

            session.PenddingData(buffer);

            while (session.TryParseHeader() && session.TryParseBody())
            {
                recievedPacket.Enqueue(new Packet
                {
                    header = session.CurrentHeader,
                    body = session.CurrentBody,
                });
                session.ClearHeader();
            }

            stream.BeginRead(reciveBuffer, 0, bufferSize, ReadCallback, null);
        }
        catch (Exception e)
        {
            Logger.LogError(e);
        }
    }

    protected virtual void OnConnected() { }
    protected abstract void OnDataReceived(in Packet packet);
}