using Unity.VisualScripting;
using UnityEngine;
using UnityEngine.EventSystems;

public class UIDragSpawner : MonoBehaviour, IBeginDragHandler, IDragHandler, IEndDragHandler
{
    public GameObject prefabToSpawn;  
    public Canvas canvas;            
    private RectTransform rectTransform;
    private CanvasGroup canvasGroup;
    private GameObject dragPreview;

    void Awake()
    {
        rectTransform = GetComponent<RectTransform>();
        //canvasGroup = gameObject.AddComponent<CanvasGroup>();
        canvasGroup = gameObject.GetOrAddComponent<CanvasGroup>(); 
    }

    public void OnBeginDrag(PointerEventData eventData)
    {
        if (canvasGroup == null)
            canvasGroup = gameObject.AddComponent<CanvasGroup>();
        canvasGroup.alpha = 0.6f;
        canvasGroup.blocksRaycasts = false;
         
        dragPreview = Instantiate(gameObject, canvas.transform);
        dragPreview.GetComponent<CanvasGroup>().blocksRaycasts = false;
    }

    public void OnDrag(PointerEventData eventData)
    {
        if (dragPreview)
        {
            dragPreview.GetComponent<RectTransform>().position = eventData.position;
        }
    }

    public void OnEndDrag(PointerEventData eventData)
    {
        canvasGroup.alpha = 1f;
        canvasGroup.blocksRaycasts = true;

        if (dragPreview)
            Destroy(dragPreview);
         
        Ray ray = Camera.main.ScreenPointToRay(eventData.position);
        if (Physics.Raycast(ray, out RaycastHit hit))
        { 
            Instantiate(prefabToSpawn, hit.point, Quaternion.identity);
        }
    }
}