using System;
using System.Collections.Generic;
using System.Threading;
using Cysharp.Threading.Tasks;
using RebootKit.Engine.Simulation;
using Unity.Collections;
using Unity.Netcode;
using UnityEngine;
using Logger = RebootKit.Engine.Foundation.Logger;

namespace RebootKit.Engine.Main {
    class NetworkClientState {
        public ulong ClientID;
        public bool IsWorldLoaded;
        public bool AreActorsSynced;
        public bool IsReadyForActorsSync;
        public int ActorsSyncPacketsLeft;

        public bool IsReady;
    }

    public class NetworkSystem : NetworkBehaviour {
        static readonly Logger s_Logger = new Logger(nameof(NetworkSystem));

        [field: SerializeField] public ActorsManager Actors { get; private set; }

        readonly Dictionary<ulong, NetworkClientState> m_Clients = new Dictionary<ulong, NetworkClientState>();

        FixedString512Bytes m_WorldID = new FixedString512Bytes("");
        bool m_IsChangingWorld = false;

        void Awake() {
            RR.NetworkSystemInstance = this;
        }

        public override void OnNetworkSpawn() {
            base.OnNetworkSpawn();

            NetworkManager.Singleton.OnClientConnectedCallback += OnClientConnected;
            NetworkManager.Singleton.OnClientDisconnectCallback += OnClientDisconnect;
        }

        public override void OnNetworkDespawn() {
            base.OnNetworkDespawn();

            NetworkManager.Singleton.OnClientConnectedCallback -= OnClientConnected;
            NetworkManager.Singleton.OnClientDisconnectCallback -= OnClientDisconnect;
        }

        void OnClientConnected(ulong clientID) {
            if (!IsServer) {
                return;
            }

            s_Logger.Info($"OnClientConnected: {clientID}");

            NetworkClientState newClientState = new NetworkClientState {
                ClientID = clientID,
                IsWorldLoaded = false,
                AreActorsSynced = false,
                IsReadyForActorsSync = false,
                IsReady = false
            };
            m_Clients.Add(clientID, newClientState);

            if (!m_WorldID.IsEmpty) {
                s_Logger.Info($"Synchronizing world load for client {clientID} with world ID '{m_WorldID}'");
                ClientLoadWorldRpc(m_WorldID.ToString(), RpcTarget.Single(clientID, RpcTargetUse.Temp));
            }
        }

        void OnClientDisconnect(ulong clientID) {
            if (!IsServer) {
                return;
            }
            
            s_Logger.Info($"OnClientDisconnect: {clientID}");
            m_Clients.Remove(clientID);
        }
        
        internal NetworkClientState GetClientState(ulong clientID) {
            if (m_Clients.TryGetValue(clientID, out NetworkClientState clientState)) {
                return clientState;
            }

            s_Logger.Error($"Client state for {clientID} not found.");
            return null;
        }

        public void SetCurrentWorld(string worldID) {
            if (!IsServer) {
                s_Logger.Error("Only server can set the current world.");
                return;
            }

            if (m_IsChangingWorld) {
                s_Logger.Error($"Already changing world to '{m_WorldID}'. Please wait until the current world change is complete.");
                return;
            }

            WorldConfigAsset worldConfigAsset = RR.GetWorldConfigAsset(worldID);
            if (worldConfigAsset is null) {
                s_Logger.Error($"Failed to set current world: World config asset for '{worldID}' not found.");
                return;
            }

            m_WorldID = worldID;

            foreach (KeyValuePair<ulong, NetworkClientState> kv in m_Clients) {
                kv.Value.IsWorldLoaded = false;
                kv.Value.AreActorsSynced = false;
                kv.Value.IsReadyForActorsSync = false;
                kv.Value.IsReady = false;
            }

            ServerLoadWorldAsync(worldConfigAsset, destroyCancellationToken).Forget();
        }

        async UniTask ServerLoadWorldAsync(WorldConfigAsset asset, CancellationToken cancellationToken) {
            s_Logger.Info($"ServerLoadWorldAsync: {asset.Config.name}");

            m_IsChangingWorld = true;

            RR.World.Unload();
            RR.CloseMainMenu();

            await RR.World.LoadAsync(asset.Config, cancellationToken);

            m_IsChangingWorld = false;

            NetworkClientState localClientState = GetClientState(NetworkManager.Singleton.LocalClientId);
            localClientState.IsReady = true;

            RR.GameInstance.PlayerBecameReady(localClientState.ClientID);

            ClientLoadWorldRpc(asset.name, RpcTarget.NotMe);
        }

        [Rpc(SendTo.SpecifiedInParams, Delivery = RpcDelivery.Reliable)]
        void ClientLoadWorldRpc(string worldID, RpcParams rpcParams) {
            WorldConfigAsset worldConfigAsset = RR.GetWorldConfigAsset(worldID);
            if (worldConfigAsset is null) {
                s_Logger.Error($"World config asset for '{worldID}' not found.");
                RR.Disconnect();
                return;
            }

            ClientLoadWorldAsync(worldID, destroyCancellationToken).Forget();
        }

        async UniTask ClientLoadWorldAsync(string worldID, CancellationToken cancellationToken) {
            s_Logger.Info($"ClientLoadWorldAsync: {worldID}");

            WorldConfigAsset worldConfigAsset = RR.GetWorldConfigAsset(worldID);
            if (worldConfigAsset is null) {
                s_Logger.Error($"World config asset for '{worldID}' not found.");
                return;
            }

            RR.World.Unload();
            RR.CloseMainMenu();

            await RR.World.LoadAsync(worldConfigAsset.Config, cancellationToken);

            m_WorldID = worldID;
            ClientLoadedWorldRpc(worldID);
        }

        [Rpc(SendTo.Server, Delivery = RpcDelivery.Reliable)]
        void ClientLoadedWorldRpc(string worldID, RpcParams rpcParams = default) {
            ulong clientID = rpcParams.Receive.SenderClientId;

            if (!m_WorldID.Equals(worldID)) {
                s_Logger.Error($"Client {clientID} tried to load world '{worldID}', but server is in world '{m_WorldID}'.");
                NetworkManager.Singleton.DisconnectClient(clientID, "World mismatch!");
                return;
            }

            if (m_Clients.TryGetValue(clientID, out NetworkClientState clientState)) {
                clientState.IsWorldLoaded = true;
                clientState.IsReadyForActorsSync = false;
                Actors.SynchronizeActorsForClient(clientID);
            } else {
                NetworkManager.Singleton.DisconnectClient(clientID, "Client is not registered!");
            }
        }
        
        internal void ClientSynchronizedActors(ulong clientID) {
            NetworkClientState clientState = GetClientState(clientID);
            if (clientState is null) {
                s_Logger.Error($"Client state for {clientID} not found.");
                return;
            }

            clientState.IsReady = true;
            RR.GameInstance.PlayerBecameReady(clientID);
        }
    }
}