using System;
using System.Collections.Generic;
using System.Reflection;

namespace Mistox.Attributes {

    public class NetworkPacketDictionary {
    
        // Fills out the NetworkPacket Lookup Dictionary
        public static readonly Dictionary<ushort, Type> PacketLookupTable = new();
        public static readonly Dictionary<Type, ushort> PacketIDTable = new();

        // Have a way to assign a number to the packet that will run the same ever time
        static ushort GetDeterministicHashCode(string str) {
            unchecked {
                uint hash = 2166136261;
                foreach (char c in str) {
                    hash = (hash ^ c) * 16777619;
                }
                return (ushort)(hash % 0xFFFF);
            }
        }

        // Map all packets to a number [ Error on packet collisions ]
        public static void BuildNetworkPacketList() {
            Assembly[] assemblies = AppDomain.CurrentDomain.GetAssemblies();
            foreach (Assembly assembly in assemblies) {
                Type[] allClasses = assembly.GetTypes();
                foreach( Type cur in allClasses) {
                    mPacket attribute = cur.GetCustomAttribute<mPacket>(false);
                    if (attribute != null) {

                        // Generate a deterministic 16-bit ID based on the Type's FullName
                        string identifier = cur.FullName ?? cur.Name;
                        ushort packetId = GetDeterministicHashCode(identifier);

                        if (PacketLookupTable.ContainsKey(packetId)) {
                            throw new Exception($"CRITICAL: Duplicate Packet ID detected! ID {packetId} is used by both {PacketLookupTable[packetId].Name} and {cur.Name}");
                        }
                        PacketLookupTable[packetId] = cur;
                        PacketIDTable[cur] = packetId;
                    }
                }
            }
        }

    }

}