using System;

namespace XWorld.Framework.Protocol
{
    public enum Channel : byte
    {
        Framework = 0, // 匹配/心跳/大厅等框架消息
        Game = 1,      // 转发给具体小游戏房间的业务消息
    }

    // 一帧线网消息
    public readonly struct Frame
    {
        public readonly Channel Channel;
        public readonly ushort Opcode;
        public readonly byte[] Payload;

        public Frame(Channel channel, ushort opcode, byte[] payload)
        {
            Channel = channel;
            Opcode = opcode;
            Payload = payload ?? Array.Empty<byte>();
        }
    }

    public static class FrameCodec
    {
        // 线网: [channel:u8][opcode:u16 LE][payloadLen:varuint][payload]
        public static byte[] Encode(Frame frame)
        {
            var w = new PacketWriter(frame.Payload.Length + 8);
            w.WriteByte((byte)frame.Channel);
            w.WriteUInt16(frame.Opcode);
            w.WriteBytes(frame.Payload); // 自带 varuint 长度前缀
            return w.ToArray();
        }

        public static Frame Decode(byte[] data)
        {
            var r = new PacketReader(data);
            var channel = (Channel)r.ReadByte();
            ushort opcode = r.ReadUInt16();
            byte[] payload = r.ReadBytes();
            return new Frame(channel, opcode, payload);
        }
    }
}