using System.Collections.Generic;
using UnityEngine;
using UnityEngine.EventSystems;
using UnityEngine.UI;

/// <summary>
/// ͨÓÃÍÏק×é¼þ
/// </summary>
public class DragUIItem :MonoBehaviour,IDragHandler,IBeginDragHandler,IEndDragHandler
{

    private RectTransform rectTransform;
    private Canvas canvas;
    private Vector2 startPosition;
    private bool restrictToCanvas = true;
    private LayoutGroup parentLayoutGroup;

   

    private void Awake()
    {
        rectTransform = GetComponent<RectTransform>();
        canvas = GetComponentInParent<Canvas>();
        startPosition = rectTransform.anchoredPosition;
        parentLayoutGroup = GetComponentInParent<LayoutGroup>();
    }

    public void OnBeginDrag(PointerEventData eventData)
    {
        if (parentLayoutGroup != null)
            parentLayoutGroup.enabled = false;
        parentLayoutGroup.GetComponent<ContentSizeFitter>().enabled = false;
    }

    public void OnDrag(PointerEventData eventData)
    {
        if (RectTransformUtility.ScreenPointToWorldPointInRectangle(
            rectTransform,
            eventData.position,
            canvas.worldCamera,
            out Vector3 worldPosition))
        {
            rectTransform.position = worldPosition;

            if (restrictToCanvas)
                RestrictToCanvasBounds();
        }
    }

    public void OnEndDrag(PointerEventData eventData)
    {
        parentLayoutGroup.enabled = true;
        parentLayoutGroup.GetComponent<ContentSizeFitter>().enabled = true;
      
    }

    private void RestrictToCanvasBounds()
    {
        Vector3[] corners = new Vector3[4];
        canvas.GetComponent<RectTransform>().GetWorldCorners(corners);

        Vector3 min = corners[0];
        Vector3 max = corners[2];

        Vector3 pos = rectTransform.position;
        pos.x = Mathf.Clamp(pos.x, min.x, max.x);
        pos.y = Mathf.Clamp(pos.y, min.y, max.y);
        rectTransform.position = pos;
    }

    public void ResetPosition()
    {
        rectTransform.anchoredPosition = startPosition;
    }
}