using System.Collections.Generic;
using UnityEngine;

namespace MedievalShopkeeper
{
    public class Shelf : Interactable
    {
        [Header("Shelf Settings")]
        [Tooltip("The maximum amount of items this shelf can hold.")]
        [SerializeField] private int maxCapacity = 10;
        
        [Tooltip("Transforms where visual prefabs should be spawned. The array size visually dictates capacity layout (can be fewer than maxCapacity, just overlaps/stacks visually).")]
        [SerializeField] private Transform[] displaySpots;

        [Header("Current Status (Read-Only)")]
        [SerializeField] private ItemData assignedItem;
        [SerializeField] private int currentStock = 0;

        private List<GameObject> visualPrefabs = new List<GameObject>();

        public ItemData AssignedItem => assignedItem;
        public int CurrentStock => currentStock;

        public override string InteractionPrompt 
        {
            get
            {
                if (assignedItem != null)
                {
                    return $"Restock {assignedItem.itemName} ({currentStock}/{maxCapacity})";
                }
                return "Stock Shelf (Empty)";
            }
        }

        public override void Interact(PlayerController player)
        {
            base.Interact(player);

            if (UIManager.Instance != null)
            {
                UIManager.Instance.OpenShelfMenu(this, player);
            }
            else
            {
                // Fallback to auto-stocking if no UI manager exists
                StockFromPlayer(player);
            }
        }

        public void StockFromPlayer(PlayerController player)
        {
            if (!player.IsCarryingItem)
            {
                Debug.Log("[Shelf] Player is not carrying any stock box.");
                return;
            }

            GameObject carriedObj = player.CurrentCarriedItem;
            StockBox stockBox = carriedObj.GetComponent<StockBox>();

            if (stockBox == null)
            {
                Debug.LogWarning("[Shelf] Carried item is not a StockBox!");
                return;
            }

            // Dynamically assign item if empty
            if (currentStock == 0)
            {
                assignedItem = stockBox.itemData;
            }

            // Check if items match
            if (assignedItem != stockBox.itemData)
            {
                Debug.Log($"[Shelf] Mismatch! Shelf holds {assignedItem.itemName}, but box contains {stockBox.itemData.itemName}.");
                return;
            }

            // Calculate how much to transfer
            int spaceAvailable = maxCapacity - currentStock;
            if (spaceAvailable <= 0)
            {
                Debug.Log("[Shelf] Shelf is already full!");
                return;
            }

            int transferAmount = Mathf.Min(spaceAvailable, stockBox.quantity);
            
            // Transfer
            currentStock += transferAmount;
            stockBox.RemoveQuantity(transferAmount);

            Debug.Log($"[Shelf] Restocked {transferAmount}x {assignedItem.itemName}. Shelf is now at {currentStock}/{maxCapacity}.");

            UpdateVisuals();

            // If box is empty, drop and destroy it
            if (stockBox.quantity <= 0)
            {
                GameObject dropped = player.DropCarriedItem();
                if (dropped != null) Destroy(dropped);
            }
        }

        public void EmptyShelf()
        {
            if (currentStock <= 0 || assignedItem == null)
            {
                Debug.Log("[Shelf] Shelf is already empty.");
                return;
            }

            // Return items to virtual Shop Inventory
            if (ShopInventory.Instance != null)
            {
                ShopInventory.Instance.AddStock(assignedItem, currentStock);
                Debug.Log($"[Shelf] Emptied {currentStock}x {assignedItem.itemName} back to Shop Inventory.");
            }
            else
            {
                Debug.LogWarning("[Shelf] No ShopInventory found to return items to! Items lost.");
            }

            currentStock = 0;
            assignedItem = null;
            UpdateVisuals();
        }

        public bool HasStock => currentStock > 0 && assignedItem != null;

        /// <summary>
        /// Called by NPCs when they want to take an item to put in their basket.
        /// </summary>
        public bool TryTakeItem(out ItemData purchasedItem)
        {
            purchasedItem = null;
            if (currentStock > 0 && assignedItem != null)
            {
                purchasedItem = assignedItem;
                currentStock--;

                if (currentStock == 0)
                {
                    assignedItem = null; // Free up the shelf for a different item if desired
                }

                UpdateVisuals();
                return true;
            }
            return false;
        }

        private void UpdateVisuals()
        {
            // Clear old visuals
            foreach (var vis in visualPrefabs)
            {
                if (vis != null) Destroy(vis);
            }
            visualPrefabs.Clear();

            if (assignedItem == null || assignedItem.displayPrefab == null || displaySpots == null || displaySpots.Length == 0) return;

            // Spawn new visuals based on stock
            // We map the stock linearly across available display spots.
            int visualsToSpawn = Mathf.Min(currentStock, displaySpots.Length);
            
            for (int i = 0; i < visualsToSpawn; i++)
            {
                GameObject vis = Instantiate(assignedItem.displayPrefab, displaySpots[i].position, displaySpots[i].rotation, displaySpots[i]);
                vis.transform.localScale = assignedItem.displayScale;
                
                // Destroy any colliders on the visual so it doesn't block rays
                foreach(var col in vis.GetComponentsInChildren<Collider>())
                {
                    Destroy(col);
                }
                
                visualPrefabs.Add(vis);
            }
        }
    }
}