using System;
using NUnit.Framework;
using RebootKit.Engine.Foundation;
using RebootKit.Engine.Main;
using Unity.Collections;
using Unity.Collections.LowLevel.Unsafe;
using Unity.Netcode;
using UnityEngine;
using Logger = RebootKit.Engine.Foundation.Logger;

namespace RebootKit.Engine.Simulation {
    public interface ISerializableEntity {
        void Serialize(FastBufferWriter writer);
        void Deserialize(FastBufferReader reader);

        // @NOTE: -1 means use the default size and have hope it will fit.
        int MinimumSizeInBytes() { return -1; }
    }

    public interface IActorData : ISerializableEntity { }

    public class NoActorData : IActorData {
        public void Serialize(FastBufferWriter writer) { }

        public void Deserialize(FastBufferReader reader) { }
    }

    public static class DataSerializationUtils {
        public const int k_DefaultMessageSize = 256;

        public static NativeArray<byte> Serialize<TEntity>(TEntity entity,
                                                                      Allocator allocator = Allocator.Temp)
            where TEntity : ISerializableEntity {
            int size = entity.MinimumSizeInBytes();
            if (size < 0) {
                size = k_DefaultMessageSize;
            }

            using FastBufferWriter writer = new FastBufferWriter(size, allocator);
            if (writer.TryBeginWrite(size)) {
                entity.Serialize(writer);

                int length = writer.Length;
                NativeArray<byte> data = new NativeArray<byte>(length, allocator);

                unsafe {
                    void* dst = data.GetUnsafePtr();
                    void* src = writer.GetUnsafePtr();
                    Buffer.MemoryCopy(src, dst, length, length);
                }

                return data;
            }

            return default;
        }

        public static void Deserialize<TEntity>(NativeArray<byte> data, ref TEntity entity)
            where TEntity : ISerializableEntity {
            using FastBufferReader reader = new FastBufferReader(data, Allocator.Temp);
            if (reader.TryBeginRead(data.Length)) {
                entity.Deserialize(reader);
            }
        }
    }

    public struct ActorCommand : INetworkSerializable {
        public ulong ActorID;
        public ulong ClientID;
        public ushort CommandID;
        public NativeArray<byte> Data;

        public void NetworkSerialize<T>(BufferSerializer<T> serializer) where T : IReaderWriter {
            serializer.SerializeValue(ref ActorID);
            serializer.SerializeValue(ref ClientID);
            serializer.SerializeValue(ref CommandID);

            if (serializer.IsWriter) {
                bool hasData = Data.IsCreated;
                serializer.SerializeValue(ref hasData);

                if (hasData) {
                    serializer.SerializeValue(ref Data, Allocator.Temp);
                }
            } else if (serializer.IsReader) {
                bool hasData = false;
                serializer.SerializeValue(ref hasData);

                if (hasData) {
                    serializer.SerializeValue(ref Data, Allocator.Temp);
                }
            }
        }
    }

    public struct ActorEvent : INetworkSerializable {
        public ulong ActorID;
        public ulong ClientID;
        public ushort EventID;
        public NativeArray<byte> Data;

        public void NetworkSerialize<T>(BufferSerializer<T> serializer) where T : IReaderWriter {
            serializer.SerializeValue(ref ActorID);
            serializer.SerializeValue(ref ClientID);
            serializer.SerializeValue(ref EventID);

            if (serializer.IsWriter) {
                bool hasData = Data.IsCreated;
                serializer.SerializeValue(ref hasData);

                if (hasData) {
                    serializer.SerializeValue(ref Data, Allocator.Temp);
                }
            } else if (serializer.IsReader) {
                bool hasData = false;
                serializer.SerializeValue(ref hasData);

                if (hasData) {
                    serializer.SerializeValue(ref Data, Allocator.Temp);
                }
            }
        }
    }

    public abstract class Actor : MonoBehaviour {
        static readonly Logger s_ActorLogger = new Logger(nameof(Actor));

        [field: SerializeField, TriInspector.ReadOnly] public string SourceActorPath { get; internal set; } = "";
        [field: SerializeField, ReadOnly] public ulong ActorID { get; internal set; }

        [NonSerialized] internal IActorData Data;

        public bool IsDataDirty { get; protected internal set; }

        internal ActorsManager Manager;

        internal IActorData InternalCreateActorData() {
            return CreateActorData();
        }

        internal void HandleActorCommand(ActorCommand actorCommand) {
            if (!RR.IsServer()) {
                s_ActorLogger.Error($"Only the server can handle actor commands. Actor: {name} (ID: {ActorID})");
                return;
            }

            if (Manager is null) {
                s_ActorLogger.Error($"Cannot handle command because Manager is null for actor {name} (ID: {ActorID})");
                return;
            }

            if (actorCommand.ActorID != ActorID) {
                s_ActorLogger
                    .Error($"Actor command ActorID {actorCommand.ActorID} does not match this actor's ID {ActorID}");
                return;
            }

            OnActorCommandServer(actorCommand);
        }

        internal void HandleActorEvent(ActorEvent actorEvent) {
            if (Manager is null) {
                s_ActorLogger.Error($"Cannot handle event because Manager is null for actor {name} (ID: {ActorID})");
                return;
            }

            if (actorEvent.ActorID != ActorID) {
                s_ActorLogger
                    .Error($"Actor event ActorID {actorEvent.ActorID} does not match this actor's ID {ActorID}");
                return;
            }

            OnActorEventClient(actorEvent);
        }

        protected abstract IActorData CreateActorData();

        // Override this method to implement server-side logic
        public virtual void ServerTick(float deltaTime) { }

        // Override this method to implement client-side logic
        public virtual void ClientTick(float deltaTime) { }

        // @NOTE: Server-side method to handle actor commands
        protected virtual void OnActorCommandServer(ActorCommand actorCommand) { }

        // @NOTE: Client-side method to handle actor events
        protected virtual void OnActorEventClient(ActorEvent actorEvent) { }

        protected void SendActorCommand<TCmdData>(ushort commandID, ref TCmdData commandData)
            where TCmdData : struct, ISerializableEntity {
            NativeArray<byte> data = DataSerializationUtils.Serialize(commandData);
            SendActorCommand(commandID, data);
        }

        protected void SendActorCommand(ushort commandID, NativeArray<byte> data = default) {
            if (Manager is null) {
                s_ActorLogger.Error($"Cannot send command because Manager is null for actor {name} (ID: {ActorID})");
                return;
            }

            ActorCommand command = new ActorCommand {
                ActorID = ActorID,
                ClientID = NetworkManager.Singleton.LocalClientId,
                CommandID = commandID,
                Data = data
            };

            Manager.SendActorCommandToServerRpc(command);
        }

        protected void SendActorEvent(ushort eventID, NativeArray<byte> data = default) {
            if (!RR.IsServer()) {
                s_ActorLogger.Error($"Only the server can send actor events. Actor: {name} (ID: {ActorID})");
                return;
            }

            if (Manager is null) {
                s_ActorLogger.Error($"Cannot send event because Manager is null for actor {name} (ID: {ActorID})");
                return;
            }

            ActorEvent actorEvent = new ActorEvent {
                ActorID = ActorID,
                ClientID = NetworkManager.Singleton.LocalClientId,
                EventID = eventID,
                Data = data
            };

            Manager.SendActorEventToClientsRpc(actorEvent);
        }

        protected T DataAs<T>() where T : IActorData {
            if (Data is T data) {
                return data;
            }

            throw new System.InvalidCastException($"Actor data is not of type {typeof(T).Name}");
        }

        void OnValidate() {
            if (ActorID == 0) {
                ActorID = UniqueID.NewULongFromGuid();
            }
        }
    }
}