// ***********************************************************************
// Assembly         : Unity
// Author           : KimCh
// Created          : 
//
// Last Modified By : KimCh
// Last Modified On : 
// ***********************************************************************
// <copyright file= "KDraggable" company=""></copyright>
// <summary></summary>
// ***********************************************************************
using UnityEngine;
using UnityEngine.EventSystems;
using UnityEngine.UI;

public class KDraggable : MonoBehaviour, IBeginDragHandler, IDragHandler, IEndDragHandler
{
	public UnityEngine.Events.UnityEvent onDragEnd = new UnityEngine.Events.UnityEvent();

	[HideInInspector]
	public Transform parentToReturnTo = null;
	[HideInInspector]
	public Transform placeHolderParent = null;

	private GameObject _placeHolder = null;
	private LayoutElement _layoutElement;

	private void Awake()
	{
		_layoutElement = GetComponent<LayoutElement>();
	}

	public void OnBeginDrag(PointerEventData eventData)
	{
		_placeHolder = new GameObject();
		_placeHolder.transform.SetParent(this.transform.parent);

		var le = _placeHolder.AddComponent<LayoutElement>();
		le.preferredWidth = _layoutElement.preferredWidth;
		le.preferredHeight = _layoutElement.preferredHeight;
		_placeHolder.transform.SetSiblingIndex(this.transform.GetSiblingIndex());

		parentToReturnTo = this.transform.parent;
		placeHolderParent = parentToReturnTo;

		_layoutElement.ignoreLayout = true;
		this.transform.SetParent(this.transform.parent.parent);
		this.GetComponent<CanvasGroup>().blocksRaycasts = false;
	}

	public void OnDrag(PointerEventData eventData)
	{
		if (_placeHolder.transform.parent != placeHolderParent)
		{
			_placeHolder.transform.SetParent(placeHolderParent);
		}

		RectTransformUtility.ScreenPointToWorldPointInRectangle(this.transform as RectTransform, eventData.position, eventData.pressEventCamera, out var position);
		this.transform.position = position;

		int newSiblingIndex = placeHolderParent.childCount;
		for (int i = 0; i < placeHolderParent.childCount; i++)
		{
			var child = placeHolderParent.GetChild(i);
			if (child.gameObject.activeSelf && position.x < child.position.x)
			{
				newSiblingIndex = i;

				if (_placeHolder.transform.GetSiblingIndex() < newSiblingIndex)
					newSiblingIndex--;
				break;
			}
		}

		_placeHolder.transform.SetSiblingIndex(newSiblingIndex);
	}

	public void OnEndDrag(PointerEventData eventData)
	{
		_layoutElement.ignoreLayout = false;
		this.transform.SetParent(parentToReturnTo);
		this.GetComponent<CanvasGroup>().blocksRaycasts = true;
		this.transform.SetSiblingIndex(_placeHolder.transform.GetSiblingIndex());
		Destroy(_placeHolder);

		onDragEnd.Invoke();
	}
}