using System.Net.Sockets;
using Google.Protobuf;
using RPG.Network.Proto;
using RPG.Services.Core.Network;
using RPG.Services.Core.Network.Command;
using RPG.Services.Core.Session;
using RPG.Services.Gateserver.Network;

namespace RPG.Services.Gateserver.Session;
internal class NetworkSession : RPGSession
{
    private const int ReadTimeoutMs = 30000;
    private const int ReceiveBufferSize = 16384;

    private readonly byte[] _recvBuffer;

    public Socket? Socket { private get; set; }
    public PlayerGetTokenCsReq? GetTokenCsReq { get; private set; }

    public NetworkSession(ulong sessionId, ServiceBox serviceBox) : base(sessionId, serviceBox)
    {
        _recvBuffer = GC.AllocateUninitializedArray<byte>(ReceiveBufferSize);
    }

    public async Task RunAsync()
    {
        if (Socket == null) throw new InvalidOperationException("RunAsync called but socket was not set!");

        int recvBufferIdx = 0;
        Memory<byte> recvBufferMem = _recvBuffer.AsMemory();

        while (true)
        {
            int readAmount = await ReadWithTimeoutAsync(Socket, recvBufferMem[recvBufferIdx..], ReadTimeoutMs);
            if (readAmount == 0) break;

            recvBufferIdx += readAmount;

            do
            {
                NetPacket.DeserializationResult result = NetPacket.TryDeserialize(recvBufferMem[..recvBufferIdx], out NetPacket? packet, out int bytesRead);
                if (result == NetPacket.DeserializationResult.BufferExceeded) break;
                if (result == NetPacket.DeserializationResult.Corrupted) return;

                HandleSessionPacketAsync(packet!);
                Buffer.BlockCopy(_recvBuffer, recvBufferIdx, _recvBuffer, 0, recvBufferIdx -= bytesRead);
            }
            while (recvBufferIdx >= NetPacket.Overhead);
        }
    }

    public async Task SendAsync<TBody>(ushort cmdType, TBody body) where TBody : IMessage<TBody>
    {
        await SendAsync(new(cmdType, ReadOnlyMemory<byte>.Empty, body.ToByteArray()));
    }

    public async Task SendAsync(NetPacket packet)
    {
        if (Socket == null) return;

        byte[] buffer = GC.AllocateUninitializedArray<byte>(packet.Size);
        packet.Serialize(buffer);

        await Socket!.SendAsync(buffer);
    }

    private void HandleSessionPacketAsync(NetPacket packet)
    {
        switch (packet.CmdType)
        {
            case CmdType.CmdPlayerGetTokenCsReq:
                HandlePlayerGetTokenCsReq(PlayerGetTokenCsReq.Parser.ParseFrom(packet.Body.Span));
                break;
            case CmdType.CmdPlayerKeepAliveNotify:
                break;
            default:
                ForwardToGameserver(packet);
                break;
        }
    }

    private void HandlePlayerGetTokenCsReq(PlayerGetTokenCsReq req)
    {
        GetTokenCsReq = req;
        PlayerUid = uint.Parse(req.AccountUid);

        BindService(RPGServiceType.Gameserver);
    }

    private void ForwardToGameserver(NetPacket packet)
    {
        SendToService(RPGServiceType.Gameserver, ServiceCommandType.ForwardGameMessage, new CmdForwardGameMessage
        {
            SessionId = SessionId,
            CmdType = packet.CmdType,
            Payload = ByteString.CopyFrom(packet.Body.Span)
        });
    }

    private static async ValueTask<int> ReadWithTimeoutAsync(Socket socket, Memory<byte> buffer, int timeoutMs)
    {
        CancellationTokenSource cts = new(TimeSpan.FromMilliseconds(timeoutMs));
        return await socket.ReceiveAsync(buffer, cts.Token);
    }
}