using CHN;
using System;
using UnityEngine;
using UnityEngine.EventSystems;

public class UIDraggerEventArg : EventArgs
{
    private Vector3 pos;
    public Vector3 Pos { get => pos; }

    public UIDraggerEventArg(Vector3 pos)
    {
        this.pos = pos;
    }
}


public class Dragger : UnityEngine.MonoBehaviour, IBeginDragHandler, IDragHandler, IEndDragHandler
{
    public static string PathPrefab = "UI/UIDragger";
    public RectTransform rect;
    [Header("Resources")]
    private RectTransform dragArea;
    private RectTransform dragObject;

    [Header("Settings")]
    private bool topOnDrag = true;
    public bool dashBoardDrag;

    private Vector2 originalLocalPointerPosition;
    private Vector3 originalPanelLocalPosition;
    public EventHandler<UIDraggerEventArg> OnCommand { get; set; }
    public Action onBeginDrag;
    private float yMinHeight;
    public void SetDrag(RectTransform parent)
    {
        if (dragArea == null)
        {
            try
            {
                var canvas = transform.GetComponentInParent<Canvas>();
                dragArea = canvas.GetComponent<RectTransform>();
            }

            catch { Debug.LogWarning("<b>[Movable Window]</b> Drag Area has not been assigned."); }
        }
        rect = GetComponent<RectTransform>();
        var toptoolbar = FindObjectOfType<Panel_TopToolBar>();
        var topbarrect = toptoolbar.GetComponent<RectTransform>();
        yMinHeight = topbarrect.sizeDelta.y;
        baseSibling = DragObjectInternal.transform.GetSiblingIndex();
        dragObject = parent;
    }
    void OnDestroy()
    {
        if (OnCommand != null) OnCommand = null;
    }


    private RectTransform DragObjectInternal
    {
        get
        {
            if (dragObject == null) { return (transform.parent as RectTransform); }
            else { return dragObject; }
        }
    }

    private RectTransform DragAreaInternal
    {
        get
        {
            if (dragArea == null)
            {
                RectTransform canvas = transform as RectTransform;
                while (canvas.parent != null && canvas.parent is RectTransform) { canvas = canvas.parent as RectTransform; }
                return canvas;
            }
            else { return dragArea; }
        }
    }
    private int baseSibling;
    public void OnBeginDrag(PointerEventData data)
    {
        if (!Input.GetMouseButton(0))
            return;
        originalPanelLocalPosition = DragObjectInternal.localPosition;
        RectTransformUtility.ScreenPointToLocalPointInRectangle(DragAreaInternal, data.position, data.pressEventCamera, out originalLocalPointerPosition);
        if (topOnDrag == true) { DragObjectInternal.transform.SetAsLastSibling(); }
    }

    public void OnDrag(PointerEventData data)
    {
        if (!Input.GetMouseButton(0))
            return;
        Vector2 localPointerPosition;

        if (RectTransformUtility.ScreenPointToLocalPointInRectangle(DragAreaInternal, data.position, data.pressEventCamera, out localPointerPosition))
        {
            Vector3 offsetToOriginal = localPointerPosition - originalLocalPointerPosition;
            DragObjectInternal.localPosition = originalPanelLocalPosition + offsetToOriginal;
        }

        ClampToArea();
    }

    private void ClampToArea()
    {
        Vector3 pos = DragObjectInternal.localPosition;

        Vector3 minPosition = DragAreaInternal.rect.min - DragObjectInternal.rect.min;
        Vector3 maxPosition = DragAreaInternal.rect.max - DragObjectInternal.rect.max;

        pos.x = Mathf.Clamp(DragObjectInternal.localPosition.x, minPosition.x, maxPosition.x);
        pos.y = Mathf.Clamp(DragObjectInternal.localPosition.y, minPosition.y, maxPosition.y - yMinHeight);

        DragObjectInternal.localPosition = pos;
    }

    public void OnEndDrag(PointerEventData eventData)
    {
        if (!dashBoardDrag)
            DragObjectInternal.transform.SetSiblingIndex(baseSibling);

        if (OnCommand != null) OnCommand(this, new UIDraggerEventArg(DragObjectInternal.anchoredPosition));
    }
}