using UnityEngine;
using UnityEngine.EventSystems;
using UnityEngine.UI;

public class SkillDragItem : MonoBehaviour, IBeginDragHandler, IDragHandler, IEndDragHandler, IPointerDownHandler, IPointerUpHandler
{
    private Image skillIcon; // 현재 오브젝트의 이미지
    private GameObject dragPreview; // 따라다니는 복사 이미지
    private Canvas canvas; // 최상위 캔버스
    private ScrollRect parentScroll;

    public int m_skillID { get; set; }
    float clickThreshold = 10f;
    Vector2 pressPos;

    private void Start()
    {
        skillIcon = GetComponent<Image>();
        canvas = GetComponentInParent<Canvas>();
        parentScroll = GetComponentInParent<ScrollRect>();
    }

    public void OnBeginDrag(PointerEventData eventData)
    {
        parentScroll?.OnBeginDrag(eventData);

        // 프리뷰 오브젝트 생성
        dragPreview = new GameObject("DragPreview", typeof(CanvasGroup), typeof(Image));
        dragPreview.transform.SetParent(canvas.transform, false);
        dragPreview.transform.SetAsLastSibling(); // 맨 위로

        Image img = dragPreview.GetComponent<Image>();
        img.sprite = skillIcon.sprite;
        img.raycastTarget = false; // 이벤트 막지 않게
        //img.SetNativeSize(); // 원래 사이즈

        // 알파 낮춰서 느낌 주기
        dragPreview.GetComponent<CanvasGroup>().alpha = 0.7f;
    }

    public void OnDrag(PointerEventData eventData)
    {
        parentScroll?.OnDrag(eventData);

        if (!DSUtil.CheckNull(dragPreview))
        {
            // 마우스 따라다니게
            RectTransformUtility.ScreenPointToLocalPointInRectangle(
                canvas.transform as RectTransform,
                eventData.position,
                eventData.pressEventCamera,
                out Vector2 localPoint
            );
            dragPreview.transform.localPosition = localPoint;
        }
    }

    public void OnEndDrag(PointerEventData eventData)
    {
        parentScroll?.OnEndDrag(eventData);

        if (!DSUtil.CheckNull(dragPreview))
            Destroy(dragPreview); // 삭제
    }

    public void OnPointerDown(PointerEventData eventData)
    {
        pressPos = eventData.position;
    }

    public void OnPointerUp(PointerEventData eventData)
    {
        if (Vector2.Distance(pressPos, eventData.position) < clickThreshold)
            GetComponentInParent<SkillCard>().OnClick_SkillUI();
    }
}