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

/// <summary>
/// Shows the hover overlay child of an icon button while the pointer is over
/// the button or while the button is not interactable (marks the active mode).
/// </summary>
public class IconButtonHover : MonoBehaviour, IPointerEnterHandler, IPointerExitHandler
{
    [SerializeField, Tooltip("Overlay object toggled on hover / while the button is disabled.")]
    private GameObject hover;

    [SerializeField, Tooltip("Button whose interactable state drives the disabled case. Defaults to the Button on this object.")]
    private Button button;

    private bool _pointerInside;

    private void Awake()
    {
        if (!button) button = GetComponent<Button>();
    }

    private void OnDisable()
    {
        _pointerInside = false;
        Refresh();
    }

    public void OnPointerEnter(PointerEventData eventData)
    {
        _pointerInside = true;
        Refresh();
    }

    public void OnPointerExit(PointerEventData eventData)
    {
        _pointerInside = false;
        Refresh();
    }

    // Poll each frame: Button has no event for interactable changes (OverviewMenu
    // flips it on refresh), and this only runs on a handful of menu buttons.
    private void LateUpdate() => Refresh();

    private void Refresh()
    {
        bool want = _pointerInside || (button && !button.interactable);
        if (hover && hover.activeSelf != want) hover.SetActive(want);
    }
}