using System.Collections.Generic;
using UnityEngine;
using Unheimlich.Core;
using Unheimlich.Gameplay.Portals;

namespace Unheimlich.Managers
{
    /// <summary>
    /// Manages dynamic loading and unloading of rooms connected by portals.
    /// Monitors player distance to portals and loads/unloads room instances accordingly.
    /// Supports room pooling (keeping inactive rooms in memory) and distance-based activation.
    /// </summary>
    public class PortalRoomManager : Singleton<PortalRoomManager>
    {
        
        [Header("Settings")]
        [SerializeField] private float _loadDistance = 15f;
        [Tooltip("Distance at which a loaded room gets deactivated (must be > load distance to avoid flip-flop)")]
        [SerializeField] private float _deactivateDistance = 50f;
        [Tooltip("Distance at which a deactivated room gets reactivated (should be < deactivate distance)")]
        [SerializeField] private float _reactivateDistance = 30f;
        [SerializeField] private bool _keepRoomsInMemory = true;
        
        [Header("Distance Calculation")]
        [Tooltip("If true, calculates distance from player to actual room position (portal + loadRoomDistance)")]
        [SerializeField] private bool _useRealRoomDistance = true;
        
        private Transform _player;
        private Dictionary<string, LoadedRoom> _loadedRooms = new Dictionary<string, LoadedRoom>();
        private List<Portal> _registeredPortals = new List<Portal>();
        private GameObject _currentPlayerRoom = null;
        
        /// <summary>
        /// Represents a room instance that has been loaded through a portal.
        /// Caches room bounds for efficient distance calculations.
        /// </summary>
        private class LoadedRoom
        {
            public GameObject RoomInstance;
            public string RoomId;
            public Vector3 LoadPosition;
            public Portal SourcePortal;
            public Bounds CachedBounds;
            public bool BoundsCalculated = false;
        }

        private void Start()
        {
            _player = GameObject.FindGameObjectWithTag("Player")?.transform;
            if (_player == null)
                Debug.LogWarning("Player not found! Make sure your player has the 'Player' tag.");
        }

        private void Update()
        {
            if (_player == null)
                return;

            CheckPortalsForLoading();
            CheckRoomsForUnloading();
        }

        public void RegisterPortal(Portal portal)
        {
            if (!_registeredPortals.Contains(portal))
                _registeredPortals.Add(portal);
        }

        public void UnregisterPortal(Portal portal)
        {
            if (_registeredPortals.Contains(portal))
                _registeredPortals.Remove(portal);
        }

        public GameObject GetLoadedRoom(string roomId)
        {
            if (_loadedRooms.TryGetValue(roomId, out LoadedRoom loadedRoom))
                return loadedRoom.RoomInstance;

            return null;
        }

        /// <summary>
        /// Checks all registered portals and loads rooms for portals within range.
        /// Optionally accounts for the portal's configured room spawn distance.
        /// </summary>
        private void CheckPortalsForLoading()
        {
            foreach (Portal portal in _registeredPortals)
            {
                float distanceToPortal = Vector3.Distance(_player.position, portal.transform.position);
                float effectiveLoadDistance = _loadDistance;
                
                if (_useRealRoomDistance)
                    effectiveLoadDistance += portal.GetRoomLoadDistance();

                if (distanceToPortal <= effectiveLoadDistance)
                    LoadRoom(portal);
            }
        }

        /// <summary>
        /// Checks all loaded rooms and determines if they should be deactivated, reactivated, or unloaded
        /// based on distance thresholds. Prevents unloading the room the player is currently inside.
        /// </summary>
        private void CheckRoomsForUnloading()
        {
            List<string> roomsToUnload = new List<string>();
            
            UpdateCurrentPlayerRoom();
            
            foreach (var kvp in _loadedRooms)
            {
                LoadedRoom loadedRoom = kvp.Value;
                if (loadedRoom.RoomInstance == null)
                {
                    roomsToUnload.Add(kvp.Key);
                    continue;
                }
                
                if (loadedRoom.RoomInstance == _currentPlayerRoom)
                    continue;
                
                float distanceToPortal = GetDistanceToRoom(loadedRoom);
                float effectiveDeactivateDistance = _deactivateDistance;
                float effectiveReactivateDistance = _reactivateDistance;
                
                if (_useRealRoomDistance)
                {
                    float roomOffset = loadedRoom.SourcePortal.GetRoomLoadDistance();
                    effectiveDeactivateDistance += roomOffset;
                    effectiveReactivateDistance += roomOffset;
                }
                
                if (distanceToPortal > effectiveDeactivateDistance)
                {
                    if (loadedRoom.RoomInstance.activeSelf)
                        roomsToUnload.Add(kvp.Key);
                }
                else if (distanceToPortal <= effectiveReactivateDistance)
                {
                    if (!loadedRoom.RoomInstance.activeSelf)
                        loadedRoom.RoomInstance.SetActive(true);
                }
            }
            
            foreach (string roomId in roomsToUnload)
            {
                UnloadRoom(roomId);
            }
        }
        
        /// <summary>
        /// Calculates the distance from the player to a loaded room.
        /// Lazily calculates and caches room bounds on first call for performance.
        /// </summary>
        private float GetDistanceToRoom(LoadedRoom loadedRoom)
        {
            if (!loadedRoom.BoundsCalculated)
            {
                loadedRoom.CachedBounds = CalculateRoomBounds(loadedRoom.RoomInstance);
                loadedRoom.BoundsCalculated = true;
            }
            
            return Vector3.Distance(_player.position, loadedRoom.CachedBounds.center);
        }
        
        /// <summary>
        /// Calculates the combined bounding box of all renderers in a room.
        /// Used to determine room center for distance calculations.
        /// </summary>
        private Bounds CalculateRoomBounds(GameObject room)
        {
            Renderer[] renderers = room.GetComponentsInChildren<Renderer>();
            if (renderers.Length == 0)
                return new Bounds(room.transform.position, Vector3.one);
            
            Bounds bounds = renderers[0].bounds;
            for (int i = 1; i < renderers.Length; i++)
                bounds.Encapsulate(renderers[i].bounds);
            
            return bounds;
        }
        
        /// <summary>
        /// Determines which room (if any) currently contains the player.
        /// Uses collider bounds checks to detect room occupancy.
        /// </summary>
        private void UpdateCurrentPlayerRoom()
        {
            _currentPlayerRoom = null;
            
            foreach (var kvp in _loadedRooms)
            {
                LoadedRoom loadedRoom = kvp.Value;
                if (loadedRoom.RoomInstance == null)
                    continue;
                
                Collider[] roomColliders = loadedRoom.RoomInstance.GetComponentsInChildren<Collider>();
                foreach (Collider col in roomColliders)
                {
                    if (col.bounds.Contains(_player.position))
                    {
                        _currentPlayerRoom = loadedRoom.RoomInstance;
                        return;
                    }
                }
            }
        }

        /// <summary>
        /// Instantiates a room from a portal's prefab at the configured spawn point.
        /// If the room is already loaded, reactivates it instead of creating a new instance.
        /// Notifies the portal when its room is successfully loaded.
        /// </summary>
        private void LoadRoom(Portal portal)
        {
            GameObject roomPrefab = portal.GetRoomPrefab();
            if (roomPrefab == null)
            {
                Debug.LogWarning($"[LOAD] Portal {portal.name} has no prefab!");
                return;
            }
            
            string roomId = portal.GetRoomId();
            
            if (_loadedRooms.TryGetValue(roomId, out LoadedRoom existingRoom))
            {
                if (existingRoom.RoomInstance != null)
                    existingRoom.RoomInstance.SetActive(true);

                return;
            }
            
            Vector3 spawnPosition = portal.GetRoomSpawnPosition();
            Quaternion spawnRotation = portal.GetRoomSpawnRotation();
            
            
            GameObject roomInstance = Instantiate(roomPrefab, spawnPosition, spawnRotation);
            roomInstance.name = $"{roomPrefab.name}_Loaded";
            
            foreach (var renderer in roomInstance.GetComponentsInChildren<MeshRenderer>())
                renderer.gameObject.SendMessage("OnBecameVisible", SendMessageOptions.DontRequireReceiver);
            
            LoadedRoom loadedRoom = new LoadedRoom
            {
                RoomInstance = roomInstance,
                RoomId = roomId,
                LoadPosition = portal.transform.position,
                SourcePortal = portal
            };
            
            _loadedRooms.Add(roomId, loadedRoom);
            
            portal.OnRoomLoaded(roomInstance);
        }

        /// <summary>
        /// Deactivates or destroys a loaded room based on the _keepRoomsInMemory setting.
        /// If keeping in memory, the room is deactivated but not destroyed (faster to reactivate).
        /// If not keeping in memory, the room is fully destroyed and removed from tracking.
        /// Notifies the source portal when its room is unloaded.
        /// </summary>
        private void UnloadRoom(string roomId)
        {
            if (_loadedRooms.TryGetValue(roomId, out LoadedRoom loadedRoom))
            {
                if (loadedRoom.RoomInstance != null)
                {
                    if (loadedRoom.SourcePortal != null)
                        loadedRoom.SourcePortal.OnRoomUnloaded();
                    
                    if (_keepRoomsInMemory)
                        loadedRoom.RoomInstance.SetActive(false);
                    else
                    {
                        Destroy(loadedRoom.RoomInstance);
                        _loadedRooms.Remove(roomId);
                    }
                }
            }
        }
    }
}