using System.Collections.Generic;
using UnityEngine;
using UnityEngine.Events;
using System; // for Action<T>
using Core; // register with ItemManager
using AppleHills.Core.Settings; // Added for IInteractionSettings

namespace Interactions
{
    // New enum describing possible states for the slotted item
    public enum ItemSlotState
    {
        None,
        Correct,
        Incorrect,
        Forbidden
    }

    /// <summary>
    /// Saveable data for ItemSlot state
    /// </summary>
    [Serializable]
    public class ItemSlotSaveData
    {
        public ItemSlotState slotState;
        public string slottedItemSaveId;
        public string slottedItemDataId; // ItemId of the PickupItemData (for verification)
    }

    /// <summary>
    /// Interaction that allows slotting, swapping, or picking up items in a slot.
    /// ItemSlot is a CONTAINER, not a Pickup itself.
    /// </summary>
    public class ItemSlot : SaveableInteractable
    {
        // Slot visual data (for the slot itself, not the item in it)
        public PickupItemData itemData;
        public SpriteRenderer iconRenderer;
        
        // Slotted item tracking
        private PickupItemData currentlySlottedItemData;
        public SpriteRenderer slottedItemRenderer;
        private GameObject currentlySlottedItemObject;
        
        // Tracks the current state of the slotted item
        private ItemSlotState currentState = ItemSlotState.None;

        // Settings reference
        private IInteractionSettings interactionSettings;
        private IPlayerFollowerSettings playerFollowerSettings;

        /// <summary>
        /// Read-only access to the current slotted item state.
        /// </summary>
        public ItemSlotState CurrentSlottedState => currentState;

        public UnityEvent onItemSlotted;
        public UnityEvent onItemSlotRemoved;
        // Native C# event alternative for code-only subscribers
        public event Action<PickupItemData> OnItemSlotRemoved;

        public UnityEvent onCorrectItemSlotted;
        // Native C# event alternative to the UnityEvent for code-only subscribers
        public event Action<PickupItemData, PickupItemData> OnCorrectItemSlotted;

        public UnityEvent onIncorrectItemSlotted;
        // Native C# event alternative for code-only subscribers
        public event Action<PickupItemData, PickupItemData> OnIncorrectItemSlotted;

        public UnityEvent onForbiddenItemSlotted;
        
        public GameObject GetSlottedObject()
        {
            return currentlySlottedItemObject;
        }

        public void SetSlottedObject(GameObject obj)
        {
            currentlySlottedItemObject = obj;
            if (currentlySlottedItemObject != null)
            {
                currentlySlottedItemObject.SetActive(false);
            }
        }

        internal override void OnManagedAwake()
        {
            base.OnManagedAwake(); // SaveableInteractable registration
            
            // Setup visuals
            if (iconRenderer == null)
                iconRenderer = GetComponent<SpriteRenderer>();
            
            ApplyItemData();
            
            // Initialize settings references
            interactionSettings = GameManager.GetSettingsObject<IInteractionSettings>();
            playerFollowerSettings = GameManager.GetSettingsObject<IPlayerFollowerSettings>();
        }

#if UNITY_EDITOR
        /// <summary>
        /// Unity OnValidate callback. Ensures icon and data are up to date in editor.
        /// </summary>
        void OnValidate()
        {
            if (iconRenderer == null)
                iconRenderer = GetComponent<SpriteRenderer>();
            ApplyItemData();
        }
#endif

        /// <summary>
        /// Applies the item data to the slot (icon, name, etc).
        /// </summary>
        public void ApplyItemData()
        {
            if (itemData != null)
            {
                if (iconRenderer != null && itemData.mapSprite != null)
                {
                    iconRenderer.sprite = itemData.mapSprite;
                }
                gameObject.name = itemData.itemName + "_Slot";
            }
        }

        #region Interaction Logic

        /// <summary>
        /// Validation: Check if interaction can proceed based on held item and slot state.
        /// </summary>
        protected override (bool canProceed, string errorMessage) CanProceedWithInteraction()
        {
            var heldItem = FollowerController?.CurrentlyHeldItemData;
            
            // Scenario: Nothing held + Empty slot = Error
            if (heldItem == null && currentlySlottedItemObject == null)
                return (false, "This requires an item.");
            
            // Check forbidden items if trying to slot into empty slot
            if (heldItem != null && currentlySlottedItemObject == null)
            {
                var config = interactionSettings?.GetSlotItemConfig(itemData);
                var forbidden = config?.forbiddenItems ?? new List<PickupItemData>();
                
                if (PickupItemData.ListContainsEquivalent(forbidden, heldItem))
                    return (false, "Can't place that here.");
            }
            
            return (true, null);
        }

        /// <summary>
        /// Main interaction logic: Slot, pickup, swap, or combine items.
        /// Returns true only if correct item was slotted.
        /// </summary>
        protected override bool DoInteraction()
        {
            Logging.Debug("[ItemSlot] DoInteraction");
            
            var heldItemData = FollowerController.CurrentlyHeldItemData;
            var heldItemObj = FollowerController.GetHeldPickupObject();
            
            // Scenario 1: Held item + Empty slot = Slot it
            if (heldItemData != null && currentlySlottedItemObject == null)
            {
                SlotItem(heldItemObj, heldItemData);
                FollowerController.ClearHeldItem(); // Clear follower's hand after slotting
                return IsSlottedItemCorrect();
            }
            
            // Scenario 2 & 3: Slot is full
            if (currentlySlottedItemObject != null)
            {
                // Try combination if both items present
                if (heldItemData != null)
                {
                    var slottedPickup = currentlySlottedItemObject.GetComponent<Pickup>();
                    if (slottedPickup != null)
                    {
                        var comboResult = FollowerController.TryCombineItems(slottedPickup, out var combinationResultItem);
                        
                        if (comboResult == FollowerController.CombinationResult.Successful)
                        {
                            // Combination succeeded - clear slot and return false (not a "slot success")
                            ClearSlot();
                            return false;
                        }
                    }
                }
                
                // No combination or unsuccessful - perform swap
                // Step 1: Pickup from slot (follower now holds the old slotted item)
                FollowerController.TryPickupItem(currentlySlottedItemObject, currentlySlottedItemData, dropItem: false);
                ClearSlot();
                
                // Step 2: If we had a held item, slot it (follower already holding picked up item, don't clear!)
                if (heldItemData != null)
                {
                    SlotItem(heldItemObj, heldItemData);
                    // Don't clear follower - they're holding the item they picked up from the slot
                    return IsSlottedItemCorrect();
                }
                
                // Just picked up from slot - not a success
                return false;
            }
            
            // Shouldn't reach here (validation prevents empty + no held)
            return false;
        }
        
        /// <summary>
        /// Helper: Check if the currently slotted item is correct.
        /// </summary>
        private bool IsSlottedItemCorrect()
        {
            return currentState == ItemSlotState.Correct;
        }
        
        /// <summary>
        /// Helper: Clear the slot and fire removal events.
        /// </summary>
        private void ClearSlot()
        {
            var previousData = currentlySlottedItemData;
            
            // Clear the pickup's OwningSlot reference
            if (currentlySlottedItemObject != null)
            {
                var pickup = currentlySlottedItemObject.GetComponent<Pickup>();
                if (pickup != null)
                {
                    pickup.OwningSlot = null;
                }
            }
            
            currentlySlottedItemObject = null;
            currentlySlottedItemData = null;
            currentState = ItemSlotState.None;
            UpdateSlottedSprite();
            
            // Fire removal events
            onItemSlotRemoved?.Invoke();
            OnItemSlotRemoved?.Invoke(previousData);
        }
        
        #endregion
        
        #region Visual Updates

        /// <summary>
        /// Updates the sprite and scale for the currently slotted item.
        /// </summary>
        private void UpdateSlottedSprite()
        {
            if (slottedItemRenderer != null && currentlySlottedItemData != null && currentlySlottedItemData.mapSprite != null)
            {
                slottedItemRenderer.sprite = currentlySlottedItemData.mapSprite;
                // Scale sprite to desired height, preserve aspect ratio, compensate for parent scale
                float desiredHeight = playerFollowerSettings?.HeldIconDisplayHeight ?? 2.0f;
                var sprite = currentlySlottedItemData.mapSprite;
                float spriteHeight = sprite.bounds.size.y;
                Vector3 parentScale = slottedItemRenderer.transform.parent != null
                    ? slottedItemRenderer.transform.parent.localScale
                    : Vector3.one;
                if (spriteHeight > 0f)
                {
                    float uniformScale = desiredHeight / spriteHeight;
                    float scale = uniformScale / Mathf.Max(parentScale.x, parentScale.y);
                    slottedItemRenderer.transform.localScale = new Vector3(scale, scale, 1f);
                }
            }
            else if (slottedItemRenderer != null)
            {
                slottedItemRenderer.sprite = null;
            }
        }
        
        #endregion
        
        // Register with ItemManager when enabled
        private void OnEnable()
        {
            // Register as ItemSlot
            ItemManager.Instance?.RegisterItemSlot(this);
        }

        protected override void OnDestroy()
        {
            base.OnDestroy();
            
            // Unregister from slot manager
            ItemManager.Instance?.UnregisterItemSlot(this);
        }

        #region Save/Load Implementation

        protected override object GetSerializableState()
        {
            // Get slotted item save ID if there's a slotted item
            string slottedSaveId = "";
            string slottedDataId = "";
            
            if (currentlySlottedItemObject != null)
            {
                var slottedPickup = currentlySlottedItemObject.GetComponent<Pickup>();
                if (slottedPickup is SaveableInteractable saveablePickup)
                {
                    slottedSaveId = saveablePickup.SaveId;
                }
            }
            
            // Also save the itemData ID for verification
            if (currentlySlottedItemData != null)
            {
                slottedDataId = currentlySlottedItemData.itemId;
            }

            return new ItemSlotSaveData
            {
                slotState = currentState,
                slottedItemSaveId = slottedSaveId,
                slottedItemDataId = slottedDataId
            };
        }

        protected override void ApplySerializableState(string serializedData)
        {
            ItemSlotSaveData data = JsonUtility.FromJson<ItemSlotSaveData>(serializedData);
            if (data == null)
            {
                Logging.Warning($"[ItemSlot] Failed to deserialize save data for {gameObject.name}");
                return;
            }

            // Restore slot state
            currentState = data.slotState;

            // Restore slotted item if there was one
            if (!string.IsNullOrEmpty(data.slottedItemSaveId))
            {
                Logging.Debug($"[ItemSlot] Restoring slotted item: {data.slottedItemSaveId} (itemId: {data.slottedItemDataId})");
                RestoreSlottedItem(data.slottedItemSaveId, data.slottedItemDataId);
            }
        }

        /// <summary>
        /// Restore a slotted item from save data.
        /// This is called during load restoration and should NOT trigger events.
        /// </summary>
        private void RestoreSlottedItem(string slottedItemSaveId, string expectedItemDataId)
        {
            // Try to find the item in the scene by its save ID via ItemManager
            GameObject slottedObject = ItemManager.Instance?.FindPickupBySaveId(slottedItemSaveId);
            
            if (slottedObject == null && !string.IsNullOrEmpty(expectedItemDataId))
            {
                // Item not found in scene - it might be a dynamically spawned combined item
                // Try to spawn it from the itemDataId
                Logging.Debug($"[ItemSlot] Slotted item not found in scene: {slottedItemSaveId}, attempting to spawn from itemId: {expectedItemDataId}");
                
                GameObject prefab = interactionSettings?.FindPickupPrefabByItemId(expectedItemDataId);
                if (prefab != null)
                {
                    // Spawn the item (inactive, since it will be slotted)
                    slottedObject = Instantiate(prefab, transform.position, Quaternion.identity);
                    slottedObject.SetActive(false);
                    Logging.Debug($"[ItemSlot] Successfully spawned combined item for slot: {expectedItemDataId}");
                }
                else
                {
                    Logging.Warning($"[ItemSlot] Could not find prefab for itemId: {expectedItemDataId}");
                    return;
                }
            }
            else if (slottedObject == null)
            {
                Logging.Warning($"[ItemSlot] Could not find slotted item with save ID: {slottedItemSaveId}");
                return;
            }

            // Get the item data from the pickup component
            PickupItemData slottedData = null;
            var pickup = slottedObject.GetComponent<Pickup>();
            if (pickup != null)
            {
                slottedData = pickup.itemData;
                
                // Verify itemId matches if we have it (safety check)
                if (slottedData != null && !string.IsNullOrEmpty(expectedItemDataId))
                {
                    if (slottedData.itemId != expectedItemDataId)
                    {
                        Logging.Warning($"[ItemSlot] ItemId mismatch! Pickup has '{slottedData.itemId}' but expected '{expectedItemDataId}'");
                    }
                }
                
                if (slottedData == null)
                {
                    Logging.Warning($"[ItemSlot] Pickup {pickup.gameObject.name} has null itemData! Expected itemId: {expectedItemDataId}");
                    if (slottedObject != null)
                        Destroy(slottedObject);
                    return;
                }
            }
            else
            {
                Logging.Warning($"[ItemSlot] Slotted object has no Pickup component: {slottedObject.name}");
                if (slottedObject != null)
                    Destroy(slottedObject);
                return;
            }

            // Silently slot the item (no events, no interaction completion)
            // Follower state is managed separately during save/load restoration
            ApplySlottedItemState(slottedObject, slottedData, triggerEvents: false);
            
            Logging.Debug($"[ItemSlot] Successfully restored slotted item: {slottedData.itemName} (itemId: {slottedData.itemId})");
        }

        /// <summary>
        /// Core logic for slotting an item. Can be used both for normal slotting and silent restoration.
        /// NOTE: Does NOT call CompleteInteraction - the template method handles that via DoInteraction return value.
        /// NOTE: Does NOT manage follower state - caller is responsible for clearing follower's hand if needed.
        /// </summary>
        /// <param name="itemToSlot">The item GameObject to slot (or null to clear)</param>
        /// <param name="itemToSlotData">The PickupItemData for the item</param>
        /// <param name="triggerEvents">Whether to fire events</param>
        private void ApplySlottedItemState(GameObject itemToSlot, PickupItemData itemToSlotData, bool triggerEvents)
        {
            if (itemToSlot == null)
            {
                // Clear slot - also clear the pickup's OwningSlot reference
                if (currentlySlottedItemObject != null)
                {
                    var oldPickup = currentlySlottedItemObject.GetComponent<Pickup>();
                    if (oldPickup != null)
                    {
                        oldPickup.OwningSlot = null;
                    }
                }
                
                var previousData = currentlySlottedItemData;
                currentlySlottedItemObject = null;
                currentlySlottedItemData = null;
                currentState = ItemSlotState.None;
                
                // Fire native event for slot clearing (only if triggering events)
                if (previousData != null && triggerEvents)
                {
                    onItemSlotRemoved?.Invoke();
                    OnItemSlotRemoved?.Invoke(previousData);
                }
            }
            else
            {
                // Slot the item
                itemToSlot.SetActive(false);
                itemToSlot.transform.SetParent(null);
                SetSlottedObject(itemToSlot);
                currentlySlottedItemData = itemToSlotData;
                
                // Mark the pickup as picked up and track slot ownership for save/load
                var pickup = itemToSlot.GetComponent<Pickup>();
                if (pickup != null)
                {
                    pickup.IsPickedUp = true;
                    pickup.OwningSlot = this;
                }
                
                // Determine if correct
                var config = interactionSettings?.GetSlotItemConfig(itemData);
                var allowed = config?.allowedItems ?? new List<PickupItemData>();
                
                if (itemToSlotData != null && PickupItemData.ListContainsEquivalent(allowed, itemToSlotData))
                {
                    currentState = ItemSlotState.Correct;
                    
                    // Fire events if requested
                    if (triggerEvents)
                    {
                        DebugUIMessage.Show($"You correctly slotted {itemToSlotData.itemName} into: {itemData.itemName}", Color.green);
                        onCorrectItemSlotted?.Invoke();
                        OnCorrectItemSlotted?.Invoke(itemData, currentlySlottedItemData);
                    }
                }
                else
                {
                    currentState = ItemSlotState.Incorrect;
                    
                    // Fire events if requested
                    if (triggerEvents)
                    {
                        DebugUIMessage.Show("I'm not sure this works.", Color.yellow);
                        onIncorrectItemSlotted?.Invoke();
                        OnIncorrectItemSlotted?.Invoke(itemData, currentlySlottedItemData);
                    }
                }
            }
            
            UpdateSlottedSprite();
        }

        /// <summary>
        /// Public API for slotting items during gameplay.
        /// Caller is responsible for managing follower's held item state.
        /// </summary>
        public void SlotItem(GameObject itemToSlot, PickupItemData itemToSlotData)
        {
            ApplySlottedItemState(itemToSlot, itemToSlotData, triggerEvents: true);
        }

        /// <summary>
        /// Bilateral restoration entry point: Pickup calls this to offer itself to the Slot.
        /// Returns true if claim was successful, false if slot already has an item or wrong pickup.
        /// </summary>
        public bool TryClaimSlottedItem(Pickup pickup)
        {
            if (pickup == null)
                return false;

            // If slot already has an item, reject the claim
            if (currentlySlottedItemObject != null)
            {
                Logging.Warning($"[ItemSlot] Already has a slotted item, rejecting claim from {pickup.gameObject.name}");
                return false;
            }

            // Verify this pickup's SaveId matches what we expect (from our save data)
            // Note: We don't have easy access to the expected SaveId here, so we just accept it
            // The Pickup's bilateral restoration ensures it only claims the correct slot

            // Claim the pickup
            ApplySlottedItemState(pickup.gameObject, pickup.itemData, triggerEvents: false);
            
            Logging.Debug($"[ItemSlot] Successfully claimed slotted item: {pickup.itemData?.itemName}");
            return true;
        }

        #endregion
    }
}