XRLib/Assets/Scripts/SHI/modal/HorizontalSplitDrag.cs

#nullable enable
using UnityEngine;
using UnityEngine.EventSystems;
using UnityEngine.UI;

namespace SHI.modal
{
    /// <summary>
    /// 수평 레이아웃에서 두 패널의 가중치(LayoutElement.flexibleWidth)를 드래그 핸들로 조절하는 간단한 분할기입니다.
    /// </summary>
    public class HorizontalSplitDrag : MonoBehaviour, IBeginDragHandler, IDragHandler, IEndDragHandler
    {
        [SerializeField, Range(0.0f, 0.5f)] private float minLeftWeight = 0.1f;
        [SerializeField, Range(0.5f, 1.0f)] private float maxLeftWeight = 0.9f;
        [SerializeField] private bool useActualWidthForHandle = true; // 실제 패널 폭 기준 위치 보정

        private RectTransform _left;
        private RectTransform _right;
        private LayoutElement _leftLayout;
        private LayoutElement _rightLayout;
        private RectTransform _parent;
        private RectTransform _handleRect; // this splitter's rect
        private float _parentWidth; // cached on begin drag
        private float _handleY = 42; // keep original y
        private RectTransform _leftFixedPanel; // e.g., ModelDetailListView root

        private bool _lastLeftPanelActive;
        private float _lastParentWidth;

        /// <summary>
        /// 좌/우 패널을 지정하고(필요 시 좌측 고정 패널 포함) 분할기를 초기화합니다.
        /// </summary>
        public void Initialize(RectTransform left, RectTransform right, RectTransform? leftFixedPanel = null)
        {
            _left = left;
            _right = right;
            _leftFixedPanel = leftFixedPanel;
            _parent = left != null ? left.parent as RectTransform : null;
            _handleRect = transform as RectTransform;

            _leftLayout = _left != null ? _left.GetComponent<LayoutElement>() : null;
            if (_left != null && _leftLayout == null) _leftLayout = _left.gameObject.AddComponent<LayoutElement>();
            _rightLayout = _right != null ? _right.GetComponent<LayoutElement>() : null;
            if (_right != null && _rightLayout == null) _rightLayout = _right.gameObject.AddComponent<LayoutElement>();

            _lastLeftPanelActive = _leftFixedPanel != null && _leftFixedPanel.gameObject.activeInHierarchy;
            _lastParentWidth = _parent != null ? _parent.rect.width : 0f;
            RefreshPosition();
        }


        /// <inheritdoc />
        public void OnBeginDrag(PointerEventData eventData)
        {
            if (_parent != null) _parentWidth = _parent.rect.width;
            if (_handleRect != null) _handleY = _handleRect.anchoredPosition.y;
        }

        /// <summary>
        /// 부모 RectTransform pivot을 고려한 작업 영역 좌/우 경계 계산.
        /// </summary>
        private void GetWorkArea(out float minX, out float maxX, out float leftOffset)
        {
            minX = maxX = leftOffset = 0f;
            if (_parent == null) return;
            float width = _parent.rect.width;
            var pivot = _parent.pivot; // (0..1)
            float pivotOrigin = -width * pivot.x; // local 좌표계에서 좌측 경계
            leftOffset = 0f;
            if (_leftFixedPanel != null && _leftFixedPanel.gameObject.activeSelf)
                leftOffset = _leftFixedPanel.rect.width; // 고정 패널 폭만큼 이동
            minX = pivotOrigin + leftOffset;
            maxX = pivotOrigin + width; // 우측 경계 (handle 중심 좌표)
        }

        /// <inheritdoc />
        public void OnDrag(PointerEventData eventData)
        {
            if (_parent == null || _leftLayout == null || _rightLayout == null) return;
            Vector2 local;
            if (!RectTransformUtility.ScreenPointToLocalPointInRectangle(_parent, eventData.position, eventData.pressEventCamera, out local))
                return;
            float width = _parent.rect.width;
            if (width <= 0f) return;

            float minX, maxX, leftOffset;
            GetWorkArea(out minX, out maxX, out leftOffset);

            // 드래그 포인터를 작업 영역으로 정규화하여 [0..1] 비율 t 산출
            float t = Mathf.InverseLerp(minX, maxX, local.x);
            t = Mathf.Clamp01(t);

            // 가변 비율 계산 (minLeftWeight~maxLeftWeight 범위)
            float leftWeight = Mathf.Lerp(minLeftWeight, maxLeftWeight, t);
            float rightWeight = Mathf.Max(0.0001f, 1f - leftWeight);
            _leftLayout.flexibleWidth = leftWeight;
            _rightLayout.flexibleWidth = rightWeight;

            // 레이아웃 즉시 반영 후 실제 폭 기준 위치 재계산
            Canvas.ForceUpdateCanvases();
            UpdateHandlePositionFromActualWidths(minX, maxX);
        }

        /// <summary>
        /// 실제 패널 폭을 사용해 핸들 위치를 경계선(왼쪽 패널 오른쪽 끝)에 정렬.
        /// 레이아웃 그룹 padding/spacing, 고정 패널 폭을 모두 반영.
        /// </summary>
        private void UpdateHandlePositionFromActualWidths(float minX, float maxX)
        {
            if (_handleRect == null || _parent == null || _left == null) return;
            if (!useActualWidthForHandle)
            {
                // 기존 비율 방식 (보정 없이)
                float totalFlex = Mathf.Max(0.0001f, _leftLayout.flexibleWidth + _rightLayout.flexibleWidth);
                float leftWeight = Mathf.Clamp01(_leftLayout.flexibleWidth / totalFlex);
                float normalized = Mathf.InverseLerp(minLeftWeight, maxLeftWeight, Mathf.Clamp(leftWeight, minLeftWeight, maxLeftWeight));
                float xRatio = Mathf.Lerp(minX, maxX, normalized);
                _handleRect.anchoredPosition = new Vector2(xRatio, _handleY);
                return;
            }

            // 고정 패널 폭 + 가변 왼쪽 패널 실제 폭 = 경계 픽셀
            float fixedWidth = (_leftFixedPanel != null && _leftFixedPanel.gameObject.activeSelf) ? _leftFixedPanel.rect.width : 0f;
            float variableLeftWidth = _left.rect.width; // 레이아웃 적용 후 실제 계산된 폭

            // 부모 pivot 기반 local 좌표 좌측 경계
            float widthParent = _parent.rect.width;
            float origin = -widthParent * _parent.pivot.x;
            float boundaryX = origin + fixedWidth + variableLeftWidth;

            // 핸들 자체 폭 중앙 정렬 (핸들 pivot이 중앙이라고 가정)
            // 경계 근처에서 과도한 이동 방지 (clamp)
            float halfHandle = _handleRect.rect.width * 0.5f;
            float minCenter = origin + fixedWidth + halfHandle; // 최소 중앙: 고정 패널 끝 + 반 핸들
            float maxCenter = origin + widthParent - halfHandle; // 최대 중앙: 부모 우측 - 반 핸들
            float centerX = Mathf.Clamp(boundaryX, minCenter, maxCenter);
            _handleRect.anchoredPosition = new Vector2(centerX, _handleY);
        }

        /// <summary>
        /// 현재 레이아웃 상태에 맞게 드래그 핸들의 위치를 동기화합니다.
        /// </summary>
        public void RefreshPosition()
        {
            if (_parent == null || _handleRect == null || _leftLayout == null || _rightLayout == null) return;
            float width = _parent.rect.width;
            if (width <= 0f) return;

            float minX, maxX, leftOffset;
            GetWorkArea(out minX, out maxX, out leftOffset);

            Canvas.ForceUpdateCanvases();
            UpdateHandlePositionFromActualWidths(minX, maxX);
        }


        private void LateUpdate()
        {
            bool nowActive = _leftFixedPanel != null && _leftFixedPanel.gameObject.activeInHierarchy;
            float nowWidth = _parent != null ? _parent.rect.width : 0f;
            if (nowActive != _lastLeftPanelActive || !Mathf.Approximately(nowWidth, _lastParentWidth))
            {
                _lastLeftPanelActive = nowActive;
                _lastParentWidth = nowWidth;
                RefreshPosition();
            }
        }

        /// <inheritdoc />
        public void OnEndDrag(PointerEventData eventData) { }
    }
}