using UnityEngine;
using UnityEngine.EventSystems;
using UnityEngine.UI;
public class ManualScroller : MonoBehaviour, IScrollHandler, IPointerEnterHandler, IPointerExitHandler
{
    public RectTransform viewport;
    public RectTransform content;
    public Slider slider;
    public float scrollSpeed = 50.0f;
    
    private bool isMouseOver = false;
    //private Vector2 lastDragPosition;  
    void Start()
    {
        slider.onValueChanged.AddListener(OnSliderValueChanged); 
    }
    public void OnScroll(PointerEventData eventData)
    {
        if (!isMouseOver) return;

        Vector2 pos = content.anchoredPosition;
        float max = content.rect.height - viewport.rect.height;
        pos.y -= eventData.scrollDelta.y * scrollSpeed;
        if (pos.y < 0) pos.y = 0;
        if (pos.y > max) pos.y = max;
        content.anchoredPosition = pos;

        slider.value = pos.y / max;
    }
    //public void OnBeginDrag(PointerEventData eventData)
    //{
    //    if (!isMouseOver) return;
    //
    //    lastDragPosition = eventData.position;
    //}
    //public void OnDrag(PointerEventData eventData)
    //{
    //    if (!isMouseOver) return;
    //
    //    Vector2 delta = eventData.position - lastDragPosition;
    //    Vector2 pos = content.anchoredPosition;
    //    pos.y += delta.y;
    //    content.anchoredPosition = pos;
    //    lastDragPosition = eventData.position;
    //} 
    public void OnPointerEnter(PointerEventData eventData)
    {
        isMouseOver = true;
    }

    public void OnPointerExit(PointerEventData eventData)
    {
        isMouseOver = false;
    }
    public void OnSliderValueChanged(float v)
    {
        Vector2 pos = content.anchoredPosition;
        float max = content.rect.height - viewport.rect.height;
        pos.y = max * v;
        content.anchoredPosition = pos;
    }
}