using UnityEngine;
using UnityEngine.EventSystems;

public class UI_ElementMoving : MonoBehaviour, IPointerDownHandler, IPointerUpHandler
{
    public bool moving;
    private Canvas parentCanvas;

    private Vector2 clickedPivot;
    public bool isButton;
    private Vector2 startPos;

    public void Start()
    {
        startPos = transform.localPosition;
        parentCanvas = transform.root.GetComponent<Canvas>();
        Vector2 pos;

        RectTransformUtility.ScreenPointToLocalPointInRectangle(
            parentCanvas.transform as RectTransform, Input.mousePosition,
            parentCanvas.worldCamera,
            out pos);
    }

    public void Update()
    {
        if (!moving)
        {
            if (isButton)
            {
                transform.localPosition = startPos;
            }
            return;
        }

        Vector2 movePos;
        RectTransformUtility.ScreenPointToLocalPointInRectangle(
            parentCanvas.transform as RectTransform,
            Input.mousePosition, parentCanvas.worldCamera,
            out movePos);

        transform.position = parentCanvas.transform.TransformPoint(movePos - (!isButton ? clickedPivot : Vector2.zero)) + (isButton ? Vector3.forward : Vector3.zero);
    }

    public void OnPointerDown(PointerEventData eventData)
    {
        if (eventData.button == PointerEventData.InputButton.Left)
        {
            if(!GetComponent<InventoryButton>() || !GetComponent<InventoryButton>().isFast)
                moving = true;
            RectTransformUtility.ScreenPointToLocalPointInRectangle(
            parentCanvas.transform as RectTransform,
            Input.mousePosition, parentCanvas.worldCamera,
            out clickedPivot);
            clickedPivot -= new Vector2(transform.localPosition.x, transform.localPosition.y);

            var invSys = FindObjectOfType<InventorySystem>();
            for (byte x = 0; x < invSys.inv.Count; x++)
            {
                transform.parent.SetSiblingIndex(invSys.inv[x].ui_image.transform == transform ? invSys.inv.Count : x);
            }
        }
    }

    public void OnPointerUp(PointerEventData eventData)
    {
        if (eventData.button == PointerEventData.InputButton.Left)
        {
            moving = false;
            clickedPivot = Vector2.zero;
        }
    }
}