Studio/Assets/Scripts/Studio/UI/TreeView/AssetLibraryScrollRect.cs

using System;
using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using UnityEngine.Events;
using UnityEngine.EventSystems;
using UnityEngine.UI;
using Studio.UI;

namespace Studio.AssetLibraryTree
{
    public class AssetLibraryScrollRect : ScrollRect, IPointerDownHandler
    {
        public bool passDragToChildren = true;
        public UnityEvent<AssetLibraryItem, AssetLibraryItem> setToChildItem;
        public UnityEvent<AssetLibraryItem, AssetLibraryItem> setToPriorSiblingItem;
        public UnityEvent<AssetLibraryItem, AssetLibraryItem> setToNextSiblingItem;
        //public UnityEvent onSelect;
        public UnityEvent<AssetLibraryItem> onDragBegin;
        public UnityEvent<AssetLibraryItem> onDragAndDrop;
        public GameObject menuPopup;
        public AssetLibraryItem sourceItem;
        private AssetLibraryScrollItemUI hoverItemUI;
        public UnityEvent<AssetLibraryItem> onExit;
        public override void OnBeginDrag(PointerEventData eventData)
        {
            if (eventData.button != PointerEventData.InputButton.Left)
                return;

            AssetLibraryScrollItemUI itemUI = GetTargetItemUI(eventData);
            if (itemUI != null && !itemUI.isSelected)
            {
                itemUI.OnPointerClick(eventData);
            }             
            onDragBegin?.Invoke(sourceItem);
            if (!passDragToChildren)
            {
                base.OnBeginDrag(eventData);  // Allow default scrolling if needed
            }
        }

        public override void OnDrag(PointerEventData eventData)
        {
            if (eventData.button == PointerEventData.InputButton.Left)
            {
                if (hoverItemUI != null) hoverItemUI.DeactivateAllHighlights();
                AssetLibraryScrollItemUI itemUI = GetTargetItemUI(eventData);
                if (itemUI != null)
                {
                    RectTransform itemRect = itemUI.GetComponent<RectTransform>();
                    Vector2 localPoint;

                    RectTransformUtility.ScreenPointToLocalPointInRectangle(
                        itemRect,
                        eventData.position,
                        eventData.pressEventCamera,
                        out localPoint
                    );

                    float rectHeight = itemRect.rect.height;
                    float normalizedY = (localPoint.y + rectHeight / 2) / rectHeight;

                    if (normalizedY >= 0.8f)  // Upper 20%
                    {
                        itemUI.ActivateUpperHighlight();
                    }
                    else if (normalizedY <= 0.2f)  // Lower 20%
                    {
                        itemUI.ActivateLowerHighlight();
                    }
                    //else  // Middle 60%
                    //{
                    //    itemUI.ActivateMidHighlight();
                    //}
                    hoverItemUI = itemUI;
                }
            }
            if (!passDragToChildren)
            {
                base.OnDrag(eventData);
            }
        }

       

        public override void OnEndDrag(PointerEventData eventData)
        {
            if (eventData.button == PointerEventData.InputButton.Left)
            {
                if (hoverItemUI != null) hoverItemUI.DeactivateAllHighlights();

                //Add to Other Item Hierarchy
                AssetLibraryScrollItemUI itemUI = GetTargetItemUI(eventData);
                if (itemUI != null && sourceItem != null)
                {
                    RectTransform itemRect = itemUI.GetComponent<RectTransform>();  // Get RectTransform of the item
                    Vector2 localPoint;

                    // Convert screen position to local position within the item
                    RectTransformUtility.ScreenPointToLocalPointInRectangle(
                        itemRect,
                        eventData.position,
                        eventData.pressEventCamera,
                        out localPoint
                    );

                    float rectHeight = itemRect.rect.height;  // Height of the item's RectTransform
                    float normalizedY = (localPoint.y + rectHeight / 2) / rectHeight;  // Normalize to 0 (bottom) to 1 (top)

                    hoverItemUI = itemUI;
                    AssetLibraryItem destItem = itemUI.currentItem;

                    if (destItem == null)
                        return;

                    if (normalizedY >= 0.8f)
                    {
                        setToPriorSiblingItem?.Invoke(sourceItem, destItem);
                    }
                    else if (normalizedY <= 0.2f)
                    {
                        setToNextSiblingItem?.Invoke(sourceItem, destItem);
                    }
                    else
                    {
                        setToChildItem?.Invoke(sourceItem, destItem);
                    }
                    sourceItem = null; 
                } 
                onDragAndDrop?.Invoke(sourceItem);
                sourceItem = null;
            }
            if (!passDragToChildren)
            {
                base.OnEndDrag(eventData);
            }
        }
        public void OnPointerDown(PointerEventData eventData)
        {
            if (eventData.button == PointerEventData.InputButton.Left)
            {
                AssetLibraryScrollItemUI itemUI = GetTargetItemUI(eventData);
                if (itemUI != null)
                {
                    sourceItem = itemUI.currentItem;
                }

            }
        }
        public void OnPointerUp(PointerEventData eventData)
        {
            if (eventData.button == PointerEventData.InputButton.Right)
            {
                if (menuPopup != null)
                {
                    menuPopup.SetActive(true);
                }
            }
        }
        private AssetLibraryScrollItemUI GetTargetItemUI(PointerEventData eventData)
        {
            PointerEventData pointerData = new PointerEventData(EventSystem.current)
            {
                position = eventData.position  // Get mouse position at drag end
            };

            var results = new List<RaycastResult>();
            EventSystem.current.RaycastAll(pointerData, results);  // Raycast against UI elements

            AssetLibraryScrollItemUI itemUI = null;
            foreach (var result in results)
            {
                itemUI = result.gameObject.GetComponent<AssetLibraryScrollItemUI>();
                if (itemUI != null)  // Exclude the dragged item itself
                {
                    break;
                }
            }
            if (itemUI != null && itemUI.GetComponentInParent<AssetLibraryScrollRect>() == this)
                return itemUI;

            return null;
        }
        public bool IsPointerOverScrollRect()
        { 
            return RectTransformUtility.RectangleContainsScreenPoint(
                GetComponent<RectTransform>(), Input.mousePosition);
        }


        //public void OnPointerExit(PointerEventData eventData)
        //{
        //    onExit?.Invoke(null);
        //}
    }
}