using System;
using System.Collections;
using System.Collections.Generic;
using System.Net;
using System.Reflection;
using System.Text;
using CLre_server.API.Engines;
using CLre_server.API.MainServer;
using Game.CommonComponents;
using HarmonyLib;
using Svelto.DataStructures;
using Svelto.ECS;
using User.Server;

namespace CLre_server.WebStatus
{
    public static class StatusEndpoints
    {
        private struct ServerStateCache
        {
            public List<PlayerData> OnlinePlayers;

            public int MaxPlayers;

            public RunState State;

            public static ServerStateCache Empty()
            {
                return new ServerStateCache
                {
                    OnlinePlayers = new List<PlayerData>(),
                    MaxPlayers = -1,
                    State = RunState.Initialising,
                };
            }

            public string Json()
            {
                // Unity's built-in JSON serializer does not work with arrays or lists :(
                // I miss Newtonsoft...
                StringBuilder sb = new StringBuilder($"{{\"PlayersMax\":{MaxPlayers},\"PlayerCount\":{OnlinePlayers.Count},\"Status\":\"{State.ToString()}\",\"OnlinePlayers\":[");
                foreach (PlayerData p in OnlinePlayers.ToArray())
                {
                    sb.Append(UnityEngine.JsonUtility.ToJson(p));
                    sb.Append(",");
                }
                if (OnlinePlayers.Count > 0) sb.Remove(sb.Length - 1, 1);
                sb.Append("]}");
                return sb.ToString();
            }
        }

        [Serializable]
        private struct PlayerData
        {
            public string id;
            public string name;
            public bool isDev;
            public float x;
            public float y;
            public float z;
        }

        private enum RunState : short
        {
            Initialising,
            Initialised,
            Online,
            Quitting,
        }
        
        private class StatusPollingEngine : ServerEnginePostBuild
        {
            public override void Ready()
            {
                API.Utility.Logging.MetaLog("StatusPolling Engine ready");
                pollLoop().Run();
            }

            public override IEntitiesDB entitiesDB { get; set; }
            public override IEntityFactory entityFactory { get; set; }

            private delegate void PlayerPositionFunc();

            private PlayerPositionFunc _playerPositionFunc = null;

            private IEnumerator pollLoop()
            {
                FieldInfo f = AccessTools.Field(AccessTools.TypeByName("User.Server.AccountExclusiveGroups"), "accountGroup");
                ExclusiveGroup accountGroup = (ExclusiveGroup) f.GetValue(null);
                while (_clState.State != RunState.Quitting)
                {
                    ReadOnlyCollectionStruct<AccountIdServerNode> accounts =
                        entitiesDB.QueryEntityViews<AccountIdServerNode>(accountGroup);
                    int index = 0;
                    foreach (AccountIdServerNode user in accounts)
                    {
                        if (index < _clState.OnlinePlayers.Count)
                        {
                            PlayerData p = _clState.OnlinePlayers[index];
                            p.id = user.accountId.publicId.ToString();
                            p.name = user.accountId.displayName;
                            p.isDev = (user.accountId.userFlags & UserFlags.Dev) == UserFlags.Dev;
                            _clState.OnlinePlayers[index] = p;
                        }
                        else
                        {
                            PlayerData p = default(PlayerData);
                            p.id = user.accountId.publicId.ToString();
                            p.name = user.accountId.displayName;
                            p.isDev = (user.accountId.userFlags & UserFlags.Dev) == UserFlags.Dev;
                            _clState.OnlinePlayers.Add(p);
                        }
                        index++;
                    }
                    if (index != 0) syncPlayerPositions();
                    if (index < _clState.OnlinePlayers.Count) _clState.OnlinePlayers.RemoveRange(index, _clState.OnlinePlayers.Count - index);
                    //API.Utility.Logging.MetaLog($"Polled {index} Online Users");
                    yield return null;
                }
            }

            private void syncPlayerPositions()
            {
                if (_playerPositionFunc == null)
                {
                    // build non-generic method using reflection
                    MethodInfo method = AccessTools.Method(typeof(StatusPollingEngine), "getPlayerPositionsGeneric",
                        generics: new[] {AccessTools.TypeByName("Game.Character.ServerCharacterPositionNode")});
                    _playerPositionFunc = API.Utility.Reflection.BuildDelegate<PlayerPositionFunc>(method, this);
                }

                _playerPositionFunc();
            }

            #pragma warning disable 0618
            private void getPlayerPositionsGeneric<T>() where T : EntityView // EntityView is deprecated lol
            {
                ReadOnlyCollectionStruct<T> scpnCollection = entitiesDB.QueryEntityViews<T>(DEPRECATED_SveltoExtensions.DEPRECATED_GROUP);
                //API.Utility.Logging.MetaLog($"Found {scpnCollection.Count} player positions");
                int i = 0;
                foreach (T scpn in scpnCollection)
                {
                    PlayerData p = _clState.OnlinePlayers[i];
                    UnityEngine.Vector3 pos = Traverse.Create(scpn).Field<IPositionComponent>("positionComponent")
                        .Value.position;
                    p.x = pos.x;
                    p.y = pos.y;
                    p.z = pos.z;
                    _clState.OnlinePlayers[i] = p;
                    i++;
                }
            }
            #pragma warning restore 0618
        }
        
        private static ServerStateCache _clState = ServerStateCache.Empty();

        internal static void Init()
        {
#if DEBUG
            API.Utility.Logging.MetaLog("Status Endpoint initialising");
#endif
            new StatusPollingEngine();
            // register API event callbacks
            Server.Instance.InitStart += (_, __) => _clState.State = RunState.Initialising;
            Server.Instance.InitComplete += (_, __) =>
            {
                _clState.State = RunState.Initialised;
                _clState.MaxPlayers = Server.Instance.GameServerSettings.GetMaxPlayers();
            };
            Server.Instance.FrameworkReady += (_, __) =>
            {
                _clState.State = RunState.Online;
                _clState.MaxPlayers = Server.Instance.GameServerSettings.GetMaxPlayers();
            };
            Server.Instance.FrameworkExit += (_, __) => _clState.State = RunState.Quitting;
        }

        [WebEndpoint("/status.json")]
        internal static void StatusJson(HttpListenerContext ctx)
        {
            ctx.Response.Headers.Add("Content-Type", "application/json");
            string json = _clState.Json();
#if DEBUG
            API.Utility.Logging.MetaLog("JSONified status: " + json);
#endif
            byte[] output = Encoding.UTF8.GetBytes(json);
            ctx.Response.OutputStream.Write(output, 0, output.Length);
        }
    }
}