using UnityEngine;
using UnityEngine.UI;
using UnityEngine.EventSystems;
using TMPro;
using System;

namespace Ashwild.Inventory
{
    public class SlotUI : MonoBehaviour, IBeginDragHandler, IDragHandler, IEndDragHandler, IDropHandler, IPointerClickHandler
    {
        [Header("References")]
        [SerializeField] private Image iconImage;
        [SerializeField] private TextMeshProUGUI quantityText;
        [SerializeField] private Image highlightImage;

        private int slotIndex;
        private Action<int, int> onSwapRequested;
        private Action<int, bool> onClicked;

        public int SlotIndex => slotIndex;

        // Static drag state shared across all slots
        private static SlotUI draggedSlot;
        private static GameObject ghostObject;
        private static Image ghostIcon;
        private static TextMeshProUGUI ghostQuantity;

        public static void SetupGhost(GameObject ghost, Image icon, TextMeshProUGUI qty)
        {
            ghostObject = ghost;
            ghostIcon = icon;
            ghostQuantity = qty;
            ghostObject.SetActive(false);
        }

        public void Initialize(int index, Action<int, int> swapCallback, Action<int, bool> clickCallback)
        {
            slotIndex = index;
            onSwapRequested = swapCallback;
            onClicked = clickCallback;
        }

        public void UpdateVisual(InventorySlot slot)
        {
            if (slot == null || slot.IsEmpty)
            {
                iconImage.gameObject.SetActive(false);
                quantityText.gameObject.SetActive(false);
            }
            else
            {
                iconImage.gameObject.SetActive(true);
                iconImage.sprite = slot.ItemData.Icon;
                bool showQty = slot.Quantity > 1;
                quantityText.gameObject.SetActive(showQty);
                if (showQty)
                    quantityText.text = slot.Quantity.ToString();
            }
        }

        public void SetSelected(bool selected)
        {
            if (highlightImage != null)
                highlightImage.gameObject.SetActive(selected);
        }

        // Drag & Drop

        public void OnBeginDrag(PointerEventData eventData)
        {
            if (eventData.button != PointerEventData.InputButton.Left) return;

            InventorySlot slot = PlayerInventory.Instance.GetSlot(slotIndex);
            if (slot == null || slot.IsEmpty) return;

            draggedSlot = this;

            // Show ghost
            if (ghostObject != null)
            {
                ghostObject.SetActive(true);
                ghostIcon.sprite = slot.ItemData.Icon;
                ghostIcon.gameObject.SetActive(true);

                bool showQty = slot.Quantity > 1;
                ghostQuantity.gameObject.SetActive(showQty);
                if (showQty)
                    ghostQuantity.text = slot.Quantity.ToString();

                ghostObject.transform.position = eventData.position;
            }

            // Make source icon semi-transparent
            Color c = iconImage.color;
            c.a = 0.4f;
            iconImage.color = c;
        }

        public void OnDrag(PointerEventData eventData)
        {
            if (draggedSlot != this) return;

            if (ghostObject != null)
                ghostObject.transform.position = eventData.position;
        }

        public void OnEndDrag(PointerEventData eventData)
        {
            if (draggedSlot != this) return;

            // Hide ghost
            if (ghostObject != null)
                ghostObject.SetActive(false);

            // Restore icon opacity
            Color c = iconImage.color;
            c.a = 1f;
            iconImage.color = c;

            draggedSlot = null;
        }

        public void OnDrop(PointerEventData eventData)
        {
            if (draggedSlot == null || draggedSlot == this) return;

            onSwapRequested?.Invoke(draggedSlot.SlotIndex, slotIndex);
        }

        public void OnPointerClick(PointerEventData eventData)
        {
            if (eventData.dragging) return;

            if (eventData.button == PointerEventData.InputButton.Right)
                onClicked?.Invoke(slotIndex, true);
        }
    }
}