using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using Core;
using Core.Lifecycle;
using AppleHills.Core;

namespace UI.Tracking
{
    /// <summary>
    /// Singleton manager that tracks off-screen targets and displays directional pins.
    /// Uses ManagedBehaviour pattern and lazily accesses camera via QuickAccess (like AudioManager).
    /// </summary>
    public class OffScreenTrackerManager : ManagedBehaviour
    {
        [Header("Configuration")]
        [Tooltip("Prefab for the off-screen tracking pin")]
        [SerializeField] private OffScreenPin pinPrefab;
        
        [Tooltip("Pixel padding from screen edges (pins appear this many pixels from edge)")]
        [SerializeField] private float screenPadding = 50f;
        
        [Tooltip("Buffer zone in pixels to prevent spawn/despawn flickering (spawn is stricter than despawn)")]
        [SerializeField] private float bufferZone = 100f;
        
        [Tooltip("Time in seconds a target must be off-screen before pin appears")]
        [SerializeField] private float spawnDebounceDelay = 0.3f;
        
        [Tooltip("Time in seconds a target must be on-screen before pin disappears")]
        [SerializeField] private float despawnDebounceDelay = 0.2f;
        
        [Tooltip("Update interval in seconds for checking target visibility")]
        [SerializeField] private float updateInterval = 0.1f;

        // Singleton instance
        private static OffScreenTrackerManager _instance;
        public static OffScreenTrackerManager Instance => _instance;

        // Tracking data
        private Dictionary<TrackableTarget, TargetTrackingData> _trackedTargets = new Dictionary<TrackableTarget, TargetTrackingData>();
        
        // Pin pooling
        private List<OffScreenPin> _inactivePins = new List<OffScreenPin>();
        
        // Coroutine tracking
        private Coroutine _updateCoroutine;
        
        // Auto-created canvas for pins
        private Canvas _pinCanvas;
        private RectTransform _pinContainer;

        /// <summary>
        /// Nested class to track per-target state and timers
        /// </summary>
        private class TargetTrackingData
        {
            public TrackableTarget Target;
            public OffScreenPin ActivePin;
            public float OffScreenTimer;
            public float OnScreenTimer;
            public bool IsCurrentlyOffScreen;
            
            public TargetTrackingData(TrackableTarget target)
            {
                Target = target;
                ActivePin = null;
                OffScreenTimer = 0f;
                OnScreenTimer = 0f;
                IsCurrentlyOffScreen = false;
            }
        }

        internal override void OnManagedAwake()
        {
            // Set singleton instance
            _instance = this;
        }

        internal override void OnManagedStart()
        {
            // Validate configuration
            if (pinPrefab == null)
            {
                Logging.Error("[OffScreenTrackerManager] Pin prefab not assigned!");
                return;
            }

            // Create dedicated canvas for pins
            CreatePinCanvas();

            // Subscribe to scene load events from SceneManagerService (like InputManager does)
            // This must happen in ManagedStart because SceneManagerService instance needs to be set first
            if (SceneManagerService.Instance != null)
            {
                SceneManagerService.Instance.SceneLoadCompleted += OnSceneLoadCompleted;
                Logging.Debug("[OffScreenTrackerManager] Subscribed to SceneLoadCompleted events");
            }

            // Initialize for current scene and start coroutine
            InitializeForCurrentScene();
        }

        /// <summary>
        /// Called when any scene finishes loading. Refreshes camera and restarts coroutine.
        /// </summary>
        private void OnSceneLoadCompleted(string sceneName)
        {
            Logging.Debug($"[OffScreenTrackerManager] Scene loaded: {sceneName}, reinitializing camera and coroutine");
            InitializeForCurrentScene();
        }

        /// <summary>
        /// Initialize camera reference and start/restart tracking coroutine for current scene
        /// </summary>
        private void InitializeForCurrentScene()
        {
            // Stop existing coroutine if running
            if (_updateCoroutine != null)
            {
                StopCoroutine(_updateCoroutine);
                _updateCoroutine = null;
                Logging.Debug("[OffScreenTrackerManager] Stopped previous coroutine");
            }

            // Start the tracking coroutine (camera accessed lazily via QuickAccess)
            _updateCoroutine = StartCoroutine(UpdateTrackingCoroutine());
            Logging.Debug("[OffScreenTrackerManager] Started tracking coroutine");
        }

        internal override void OnManagedDestroy()
        {
            // Unsubscribe from SceneManagerService events (like InputManager does)
            if (SceneManagerService.Instance != null)
            {
                SceneManagerService.Instance.SceneLoadCompleted -= OnSceneLoadCompleted;
            }
        }

        private void OnDestroy()
        {
            // Stop coroutine
            if (_updateCoroutine != null)
            {
                StopCoroutine(_updateCoroutine);
            }

            // Clean up pooled pins
            foreach (var pin in _inactivePins)
            {
                if (pin != null)
                {
                    Destroy(pin.gameObject);
                }
            }
            _inactivePins.Clear();

            // Clean up active pins
            foreach (var data in _trackedTargets.Values)
            {
                if (data.ActivePin != null)
                {
                    Destroy(data.ActivePin.gameObject);
                }
            }
            _trackedTargets.Clear();

            // Clean up canvas
            if (_pinCanvas != null)
            {
                Destroy(_pinCanvas.gameObject);
            }

            // Clear singleton
            if (_instance == this)
            {
                _instance = null;
            }
        }

        /// <summary>
        /// Create a dedicated canvas for pins with sort order 50
        /// </summary>
        private void CreatePinCanvas()
        {
            // Create a new GameObject for the canvas
            GameObject canvasObj = new GameObject("OffScreenPinCanvas");
            canvasObj.transform.SetParent(transform, false);

            // Add and configure Canvas
            _pinCanvas = canvasObj.AddComponent<Canvas>();
            _pinCanvas.renderMode = RenderMode.ScreenSpaceOverlay;
            _pinCanvas.sortingOrder = 50;

            // Add CanvasScaler for consistent sizing
            var scaler = canvasObj.AddComponent<UnityEngine.UI.CanvasScaler>();
            scaler.uiScaleMode = UnityEngine.UI.CanvasScaler.ScaleMode.ScaleWithScreenSize;
            scaler.referenceResolution = new Vector2(1920, 1080);
            scaler.screenMatchMode = UnityEngine.UI.CanvasScaler.ScreenMatchMode.MatchWidthOrHeight;
            scaler.matchWidthOrHeight = 0.5f;

            // Add GraphicRaycaster (required for UI)
            canvasObj.AddComponent<UnityEngine.UI.GraphicRaycaster>();

            // Get RectTransform for pin container
            _pinContainer = canvasObj.GetComponent<RectTransform>();

            Logging.Debug("[OffScreenTrackerManager] Created dedicated pin canvas with sort order 50");
        }

        /// <summary>
        /// Register a target for tracking
        /// </summary>
        public void RegisterTarget(TrackableTarget target)
        {
            if (target == null)
                return;

            if (_trackedTargets.ContainsKey(target))
            {
                Logging.Warning($"[OffScreenTrackerManager] Target {target.name} is already registered");
                return;
            }

            _trackedTargets.Add(target, new TargetTrackingData(target));
            Logging.Debug($"[OffScreenTrackerManager] Registered target: {target.name}");
        }

        /// <summary>
        /// Unregister a target from tracking
        /// </summary>
        public void UnregisterTarget(TrackableTarget target)
        {
            if (target == null)
                return;

            if (_trackedTargets.TryGetValue(target, out TargetTrackingData data))
            {
                // Despawn pin if active
                if (data.ActivePin != null)
                {
                    DespawnPin(data);
                }

                _trackedTargets.Remove(target);
                Logging.Debug($"[OffScreenTrackerManager] Unregistered target: {target.name}");
            }
        }

        /// <summary>
        /// Main update coroutine that runs every updateInterval seconds
        /// </summary>
        private IEnumerator UpdateTrackingCoroutine()
        {
            Logging.Debug("[OffScreenTrackerManager] Tracking coroutine started");
            WaitForSeconds wait = new WaitForSeconds(updateInterval);

            while (true)
            {
                yield return wait;

                // Get camera lazily via QuickAccess (like AudioManager does)
                Camera mainCamera = QuickAccess.Instance?.MainCamera;
                
                if (mainCamera == null)
                {
                    // Camera not available yet (early in boot or scene transition)
                    continue;
                }

                // Create list of targets to remove (for null cleanup)
                List<TrackableTarget> targetsToRemove = new List<TrackableTarget>();

                foreach (var kvp in _trackedTargets)
                {
                    TrackableTarget target = kvp.Key;
                    TargetTrackingData data = kvp.Value;

                    // Check if target was destroyed
                    if (target == null)
                    {
                        targetsToRemove.Add(target);
                        if (data.ActivePin != null)
                        {
                            DespawnPin(data);
                        }
                        continue;
                    }

                    // Check if target is off-screen
                    bool isOffScreen = IsTargetOffScreen(target, mainCamera);

                    // Update timers and state
                    if (isOffScreen)
                    {
                        // Target is off-screen
                        data.OffScreenTimer += updateInterval;
                        data.OnScreenTimer = 0f;

                        // Check if we should spawn a pin
                        if (!data.IsCurrentlyOffScreen && data.OffScreenTimer >= spawnDebounceDelay)
                        {
                            data.IsCurrentlyOffScreen = true;
                            SpawnPin(data);
                        }
                        // Pin updates itself every frame, no need to call UpdatePositionAndRotation here
                    }
                    else
                    {
                        // Target is on-screen
                        data.OnScreenTimer += updateInterval;
                        data.OffScreenTimer = 0f;

                        // Check if we should despawn the pin
                        if (data.IsCurrentlyOffScreen && data.OnScreenTimer >= despawnDebounceDelay)
                        {
                            data.IsCurrentlyOffScreen = false;
                            if (data.ActivePin != null)
                            {
                                DespawnPin(data);
                            }
                        }
                    }
                }

                // Clean up null targets
                foreach (var target in targetsToRemove)
                {
                    _trackedTargets.Remove(target);
                }
            }
        }

        /// <summary>
        /// Check if a target is off-screen by checking its actual bounds.
        /// - For SPAWNING: Entire object must be off-screen (all corners outside viewport)
        /// - For DESPAWNING: Any part of object on-screen triggers despawn (any corner inside viewport)
        /// Uses bufferZone to prevent flickering at boundaries.
        /// </summary>
        private bool IsTargetOffScreen(TrackableTarget target, Camera cam)
        {
            // Get the world bounds of the target
            Bounds worldBounds = target.GetWorldBounds();

            // Get the 8 corners of the bounds (we only need the min/max points in 2D)
            Vector3 min = worldBounds.min;
            Vector3 max = worldBounds.max;

            // Convert corners to screen space
            Vector3 minScreen = cam.WorldToScreenPoint(new Vector3(min.x, min.y, worldBounds.center.z));
            Vector3 maxScreen = cam.WorldToScreenPoint(new Vector3(max.x, max.y, worldBounds.center.z));

            // Check if behind camera
            if (minScreen.z < 0 && maxScreen.z < 0)
                return true;

            // Shrink detection zones to 80% of screen (10% inset on each side)
            // This makes spawn/despawn more conservative
            float insetPercent = 0.1f; // 10% on each side = 80% total
            float horizontalInset = Screen.width * insetPercent;
            float verticalInset = Screen.height * insetPercent;
            
            float screenLeft = horizontalInset;
            float screenRight = Screen.width - horizontalInset;
            float screenBottom = verticalInset;
            float screenTop = Screen.height - verticalInset;

            // Check if ENTIRELY off-screen (all corners outside viewport)
            // This is when we should spawn the pin
            bool entirelyOffScreenLeft = maxScreen.x < screenLeft;
            bool entirelyOffScreenRight = minScreen.x > screenRight;
            bool entirelyOffScreenBottom = maxScreen.y < screenBottom;
            bool entirelyOffScreenTop = minScreen.y > screenTop;

            bool entirelyOffScreen = entirelyOffScreenLeft || entirelyOffScreenRight || 
                                     entirelyOffScreenBottom || entirelyOffScreenTop;

            // Apply buffer zone to prevent flickering
            // If already off-screen, require target to move bufferZone pixels on-screen before considering it "on-screen"
            // This creates hysteresis to prevent rapid spawn/despawn cycles
            if (entirelyOffScreen)
            {
                return true; // Definitely off-screen
            }

            // Check if ANY part is on-screen (for despawn logic)
            // We add bufferZone to make despawn slightly more eager
            bool anyPartOnScreen = !(minScreen.x > screenRight - bufferZone || 
                                     maxScreen.x < screenLeft + bufferZone ||
                                     minScreen.y > screenTop - bufferZone || 
                                     maxScreen.y < screenBottom + bufferZone);

            // If any part is on-screen (with buffer), consider it "on-screen" (pin should despawn)
            return !anyPartOnScreen;
        }

        /// <summary>
        /// Spawn a pin for the given target data
        /// </summary>
        private void SpawnPin(TargetTrackingData data)
        {
            // Try to get pin from pool
            OffScreenPin pin = GetPinFromPool();

            // Initialize the pin (this also caches the target and settings)
            pin.Initialize(data.Target, screenPadding);
            
            // CRITICAL: Update position BEFORE activating to prevent flicker
            // Get camera for immediate position update
            Camera mainCamera = QuickAccess.Instance?.MainCamera;
            if (mainCamera != null)
            {
                pin.UpdatePositionAndRotation(mainCamera, screenPadding);
            }
            
            // Now activate the pin at the correct position
            pin.gameObject.SetActive(true);


            data.ActivePin = pin;

            Logging.Debug($"[OffScreenTrackerManager] Spawned pin for target: {data.Target.name}");
        }

        /// <summary>
        /// Despawn a pin and return it to the pool
        /// </summary>
        private void DespawnPin(TargetTrackingData data)
        {
            if (data.ActivePin == null)
                return;

            OffScreenPin pin = data.ActivePin;
            data.ActivePin = null;

            // Reset and return to pool
            pin.ResetPin();
            pin.gameObject.SetActive(false);
            _inactivePins.Add(pin);

            Logging.Debug($"[OffScreenTrackerManager] Despawned pin for target: {data.Target?.name ?? "null"}");
        }

        /// <summary>
        /// Get a pin from the pool or instantiate a new one
        /// </summary>
        private OffScreenPin GetPinFromPool()
        {
            // Try to reuse an inactive pin
            if (_inactivePins.Count > 0)
            {
                OffScreenPin pin = _inactivePins[_inactivePins.Count - 1];
                _inactivePins.RemoveAt(_inactivePins.Count - 1);
                return pin;
            }

            // Create a new pin
            OffScreenPin newPin = Instantiate(pinPrefab, _pinContainer);
            newPin.gameObject.SetActive(false);
            return newPin;
        }

        #region Public Configuration Accessors

        /// <summary>
        /// Get or set the screen padding in pixels
        /// </summary>
        public float ScreenPadding
        {
            get => screenPadding;
            set => screenPadding = Mathf.Max(0f, value);
        }

        /// <summary>
        /// Get or set the spawn debounce delay
        /// </summary>
        public float SpawnDebounceDelay
        {
            get => spawnDebounceDelay;
            set => spawnDebounceDelay = Mathf.Max(0f, value);
        }

        /// <summary>
        /// Get or set the despawn debounce delay
        /// </summary>
        public float DespawnDebounceDelay
        {
            get => despawnDebounceDelay;
            set => despawnDebounceDelay = Mathf.Max(0f, value);
        }

        #endregion
    }
}