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

namespace Vanguard.UI
{
    /// <summary>
    /// ScrollRect с плавным колесом: колесо задаёт целевую позицию, а контент
    /// подъезжает к ней за несколько кадров. Перетаскивание работает как обычно.
    /// </summary>
    public sealed class SmoothScrollRect : ScrollRect
    {
        public float WheelStep = 140f;
        public float Smoothing = 0.06f;

        private float _target;
        private bool _smooth;

        public override void OnScroll(PointerEventData eventData)
        {
            if (!vertical || content == null || viewport == null)
            {
                base.OnScroll(eventData);
                return;
            }

            if (!_smooth)
                _target = content.anchoredPosition.y;

            var max = Mathf.Max(0f, content.rect.height - viewport.rect.height);
            _target = Mathf.Clamp(_target + eventData.scrollDelta.y * WheelStep, -max, 0f);
            velocity = Vector2.zero;
            _smooth = true;
        }

        public override void OnBeginDrag(PointerEventData eventData)
        {
            _smooth = false;
            base.OnBeginDrag(eventData);
        }

        protected override void LateUpdate()
        {
            if (!_smooth || content == null || viewport == null)
            {
                base.LateUpdate();
                return;
            }

            var position = content.anchoredPosition;
            var max = Mathf.Max(0f, content.rect.height - viewport.rect.height);
            _target = Mathf.Clamp(_target, -max, 0f);

            var t = 1f - Mathf.Exp(-Time.unscaledDeltaTime / Mathf.Max(0.01f, Smoothing));
            var next = Mathf.Lerp(position.y, _target, t);
            if (Mathf.Abs(next - _target) < 0.5f)
            {
                next = _target;
                _smooth = false;
            }

            content.anchoredPosition = new Vector2(position.x, next);
        }
    }
}