evershade/Assets/Scripts/Controllers/InventoryItemDisplayController.cs

using TMPro;
using UnityEngine;
using UnityEngine.EventSystems;
using UnityEngine.Serialization;
using UnityEngine.UI;


// Drag Dropable
public class InventoryItemDisplayController : MonoBehaviour, IPointerDownHandler, IBeginDragHandler, IEndDragHandler,
    IDragHandler
{
    [SerializeField] private Canvas canvas;

    [FormerlySerializedAs("InventoryItem")]
    public GameItem gameItem;

    private CanvasGroup _canvasGroup;
    private Canvas _dragLayerCanvas;
    private Transform _originalParent;
    private Vector2 _originalPosition;

    private RectTransform _rectTransform;

    private void Awake()
    {
        _rectTransform = GetComponent<RectTransform>();
        _canvasGroup = GetComponent<CanvasGroup>();
        if (_canvasGroup == null) _canvasGroup = gameObject.AddComponent<CanvasGroup>();

        if (canvas == null) canvas = GameObject.Find("UICanvas").GetComponent<Canvas>();
        _dragLayerCanvas = GameObject.Find("DragLayerCanvas").GetComponent<Canvas>();
    }

    // Update is called once per frame
    private void Update()
    {
    }

    public void OnBeginDrag(PointerEventData eventData)
    {
        Debug.Log("Begin Drag");
        _originalPosition = _rectTransform.anchoredPosition;
        _canvasGroup.alpha = 0.6f;
        _canvasGroup.blocksRaycasts = false;
        _canvasGroup.interactable = false; // Disable interaction while dragging
    }

    public void OnDrag(PointerEventData eventData)
    {
        // Ensure the canvas is set
        if (canvas == null)
        {
            Debug.LogWarning("Canvas is null");
            return;
        }

        // Convert the mouse position to canvas space and update the item's position
        Vector2 localPointerPosition;
        RectTransformUtility.ScreenPointToLocalPointInRectangle(
            canvas.transform as RectTransform,
            eventData.position,
            canvas.worldCamera,
            out localPointerPosition);

        _rectTransform.localPosition = localPointerPosition;
    }

    public void OnEndDrag(PointerEventData eventData)
    {
        Debug.Log("End Drag");

        // Check if dropped on a valid slot
        var hitObjects = eventData.hovered;
        var droppedOnValidSlot = false;
        foreach (var obj in hitObjects)
            if (obj.GetComponent<InventorySlotDisplayController>() != null)
            {
                droppedOnValidSlot = true;
                break;
            }

        if (!droppedOnValidSlot)
            // Snap back to original position if not dropped in a valid slot
            _rectTransform.anchoredPosition = _originalPosition;

        _canvasGroup.alpha = 1.0f;
        _canvasGroup.blocksRaycasts = true;
        _canvasGroup.interactable = true; // Enable interaction after dragging
    }

    public void OnPointerDown(PointerEventData eventData)
    {
        Debug.Log("OnPointerDown");
    }


    public void SetItem(GameItem item)
    {
        if (item == null)
        {
            Debug.Log("Item is null!");
            gameItem = null;
            Destroy(transform.gameObject);

            return;
        }

        gameItem = item;

        Debug.Log(transform.GetChild(1));
        transform.Find("ItemName").GetComponent<TMP_Text>().text = item.itemName;
        transform.Find("qty").GetComponent<Text>().text = item.qty;
        transform.Find("Icon").GetComponent<Image>().sprite = item.icon;


        Debug.Log("completed processing set item");
    }
}