using System;

namespace XWorld.Framework.Protocol
{
    public static class DevDiscovery
    {
        public const int Port = 48923;
        public const uint ProtoVersion = 1;
        public static readonly byte[] Magic = { 0x58, 0x57, 0x44, 0x4C };
        public const byte TypeQuery = 1;
        public const byte TypeReply = 2;
    }

    public struct DevDiscoveryQuery
    {
        public uint ProtoVersion;
        public uint Nonce;
        public string Token;
    }

    public struct DevDiscoveryReply
    {
        public uint ProtoVersion;
        public uint Nonce;
        public string ServerName;
        public string GatewayUrl;
        public string ResourceBaseUrl;
        public string Token;
    }

    public static class DevDiscoveryCodec
    {
        public static byte[] EncodeQuery(DevDiscoveryQuery q)
        {
            var w = new PacketWriter(32);
            WriteHeader(w, DevDiscovery.TypeQuery);
            w.WriteVarUInt(q.ProtoVersion);
            w.WriteVarUInt(q.Nonce);
            w.WriteString(q.Token);
            return w.ToArray();
        }

        public static byte[] EncodeReply(DevDiscoveryReply r)
        {
            var w = new PacketWriter(96);
            WriteHeader(w, DevDiscovery.TypeReply);
            w.WriteVarUInt(r.ProtoVersion);
            w.WriteVarUInt(r.Nonce);
            w.WriteString(r.ServerName);
            w.WriteString(r.GatewayUrl);
            w.WriteString(r.ResourceBaseUrl);
            w.WriteString(r.Token);
            return w.ToArray();
        }

        public static bool TryDecodeQuery(byte[] data, out DevDiscoveryQuery q)
        {
            q = default;
            try
            {
                var r = new PacketReader(data);
                if (!ReadAndCheckHeader(r, DevDiscovery.TypeQuery)) return false;
                q.ProtoVersion = r.ReadVarUInt();
                q.Nonce = r.ReadVarUInt();
                q.Token = r.ReadString();
                return true;
            }
            catch (FormatException)
            {
                return false;
            }
        }

        public static bool TryDecodeReply(byte[] data, out DevDiscoveryReply reply)
        {
            reply = default;
            try
            {
                var r = new PacketReader(data);
                if (!ReadAndCheckHeader(r, DevDiscovery.TypeReply)) return false;
                reply.ProtoVersion = r.ReadVarUInt();
                reply.Nonce = r.ReadVarUInt();
                reply.ServerName = r.ReadString();
                reply.GatewayUrl = r.ReadString();
                reply.ResourceBaseUrl = r.ReadString();
                reply.Token = r.ReadString();
                return true;
            }
            catch (FormatException)
            {
                return false;
            }
        }

        private static void WriteHeader(PacketWriter w, byte type)
        {
            for (int i = 0; i < DevDiscovery.Magic.Length; i++)
            {
                w.WriteByte(DevDiscovery.Magic[i]);
            }
            w.WriteByte(type);
        }

        private static bool ReadAndCheckHeader(PacketReader r, byte expectedType)
        {
            for (int i = 0; i < DevDiscovery.Magic.Length; i++)
            {
                if (r.ReadByte() != DevDiscovery.Magic[i]) return false;
            }
            return r.ReadByte() == expectedType;
        }
    }
}