#if UNITY_EDITOR && UNITY_INPUT_SYSTEM_PROJECT_WIDE_ACTIONS
using System.Linq;
using UnityEditor;
using UnityEngine.UIElements;

namespace UnityEngine.InputSystem.Editor
{
    /// <summary>
    /// Class to handle drop from the actions tree view to the action maps list view.
    /// </summary>
    internal class DropManipulator : Manipulator
    {
        private EventCallback<int> DroppedPerformedCallback;
        private VisualElement m_OtherVerticalList;
        private ListView listView => target as ListView;
        private TreeView treeView => m_OtherVerticalList as TreeView;

        public DropManipulator(EventCallback<int> droppedPerformedCallback, VisualElement otherVerticalList)
        {
            DroppedPerformedCallback = droppedPerformedCallback;
            m_OtherVerticalList = otherVerticalList;
        }

        protected override void RegisterCallbacksOnTarget()
        {
            m_OtherVerticalList.RegisterCallback<DragUpdatedEvent>(OnDragUpdatedEvent, TrickleDown.TrickleDown);
            m_OtherVerticalList.RegisterCallback<DragPerformEvent>(OnDragPerformEvent, TrickleDown.TrickleDown);
        }

        protected override void UnregisterCallbacksFromTarget()
        {
            m_OtherVerticalList.UnregisterCallback<DragUpdatedEvent>(OnDragUpdatedEvent, TrickleDown.TrickleDown);
            m_OtherVerticalList.UnregisterCallback<DragPerformEvent>(OnDragPerformEvent, TrickleDown.TrickleDown);
        }

        private void OnDragPerformEvent(DragPerformEvent evt)
        {
            var mapsViewItem = target.panel.Pick(evt.mousePosition)?.GetFirstAncestorOfType<InputActionMapsTreeViewItem>();
            if (mapsViewItem == null)
                return;
            var index = treeView.selectedIndices.First();
            var draggedItem = treeView.GetItemDataForIndex<ActionOrBindingData>(index);
            if (!draggedItem.isAction)
                return;
            evt.StopImmediatePropagation();
            DragAndDrop.AcceptDrag();
            DroppedPerformedCallback.Invoke((int)mapsViewItem.userData);
            Reset();
            treeView.ReleaseMouse();
        }

        private int m_InitialIndex = -1;
        private void OnDragUpdatedEvent(DragUpdatedEvent evt)
        {
            var mapsViewItem = target.panel.Pick(evt.mousePosition)?.GetFirstAncestorOfType<InputActionMapsTreeViewItem>();
            if (mapsViewItem != null)
            {
                if (m_InitialIndex < 0 && listView != null)
                    m_InitialIndex = listView.selectedIndex;
                //select map item to visualize the drop
                listView?.SetSelectionWithoutNotify(new[] { (int)mapsViewItem.userData }); //the user data contains the index of the map item
                DragAndDrop.visualMode = DragAndDropVisualMode.Move;
                evt.StopImmediatePropagation();
            }
            else
                Reset();
        }

        private void Reset()
        {
            if (m_InitialIndex >= 0)
                listView?.SetSelectionWithoutNotify(new[] {m_InitialIndex}); //select the initial action map again
            m_InitialIndex = -1;
        }
    }
}
#endif