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

namespace AlicizaX.UI
{
    [DisallowMultipleComponent]
    public sealed class ItemInteractionProxy : MonoBehaviour,
        IPointerClickHandler,
        IPointerEnterHandler,
        IPointerExitHandler,
        ISelectHandler,
        IDeselectHandler,
        IMoveHandler,
        IBeginDragHandler,
        IDragHandler,
        IEndDragHandler,
        ISubmitHandler,
        ICancelHandler
    {
        private IItemInteractionHost host;
        private ItemInteractionFlags flags;
        private Selectable focusAnchor;
        private RecyclerItemSelectable ownedSelectable;
        private Scroller parentScroller;

        internal void Bind(IItemInteractionHost interactionHost)
        {
            host = interactionHost;
            flags = interactionHost?.InteractionFlags ?? ItemInteractionFlags.None;
            parentScroller = GetComponentInParent<Scroller>();
            EnsureFocusAnchor();

            if (ownedSelectable != null)
            {
                bool requiresSelection = RequiresSelection(flags);
                ownedSelectable.interactable = requiresSelection;
                ownedSelectable.enabled = requiresSelection;
            }

            InvalidateNavigationScope();
        }

        public void Clear()
        {
            host = null;
            flags = ItemInteractionFlags.None;
            parentScroller = null;

            if (ownedSelectable != null)
            {
                ownedSelectable.interactable = false;
                ownedSelectable.enabled = false;
            }

            InvalidateNavigationScope();
        }

        public Selectable GetSelectable()
        {
            EnsureFocusAnchor();
            return focusAnchor;
        }

        internal bool TryGetFocusTarget(out GameObject target)
        {
            target = null;
            if (!TryGetFocusableSelectable(out Selectable selectable))
            {
                return false;
            }

            target = selectable.gameObject;
            return target != null;
        }

        public void OnPointerClick(PointerEventData eventData)
        {
            if ((flags & ItemInteractionFlags.PointerClick) != 0)
            {
                host?.HandlePointerClick(eventData);
            }
        }

        public void OnPointerEnter(PointerEventData eventData)
        {
            if ((flags & ItemInteractionFlags.PointerEnter) != 0)
            {
                host?.HandlePointerEnter(eventData);
            }
        }

        public void OnPointerExit(PointerEventData eventData)
        {
            if ((flags & ItemInteractionFlags.PointerExit) != 0)
            {
                host?.HandlePointerExit(eventData);
            }
        }

        public void OnSelect(BaseEventData eventData)
        {
            if ((flags & ItemInteractionFlags.Select) != 0)
            {
                host?.HandleSelect(eventData);
            }
        }

        public void OnDeselect(BaseEventData eventData)
        {
            if ((flags & ItemInteractionFlags.Deselect) != 0)
            {
                host?.HandleDeselect(eventData);
            }
        }

        public void OnMove(AxisEventData eventData)
        {
            if ((flags & ItemInteractionFlags.Move) != 0)
            {
                host?.HandleMove(eventData);
            }
        }

        public void OnBeginDrag(PointerEventData eventData)
        {
            if ((flags & ItemInteractionFlags.BeginDrag) != 0)
            {
                host?.HandleBeginDrag(eventData);
                return;
            }

            parentScroller?.OnBeginDrag(eventData);
        }

        public void OnDrag(PointerEventData eventData)
        {
            if ((flags & ItemInteractionFlags.Drag) != 0)
            {
                host?.HandleDrag(eventData);
                return;
            }

            parentScroller?.OnDrag(eventData);
        }

        public void OnEndDrag(PointerEventData eventData)
        {
            if ((flags & ItemInteractionFlags.EndDrag) != 0)
            {
                host?.HandleEndDrag(eventData);
                return;
            }

            parentScroller?.OnEndDrag(eventData);
        }

        public void OnSubmit(BaseEventData eventData)
        {
            if ((flags & ItemInteractionFlags.Submit) != 0)
            {
                host?.HandleSubmit(eventData);
            }
        }

        public void OnCancel(BaseEventData eventData)
        {
            if ((flags & ItemInteractionFlags.Cancel) != 0)
            {
                host?.HandleCancel(eventData);
            }
        }

        private void EnsureFocusAnchor()
        {
            if (focusAnchor != null)
            {
                return;
            }

            focusAnchor = GetComponent<Selectable>();
            if (focusAnchor != null)
            {
                return;
            }

            ownedSelectable = GetComponent<RecyclerItemSelectable>();
            if (ownedSelectable == null)
            {
                ownedSelectable = gameObject.AddComponent<RecyclerItemSelectable>();
            }

            focusAnchor = ownedSelectable;
        }

        private bool TryGetFocusableSelectable(out Selectable selectable)
        {
            EnsureFocusAnchor();
            if (IsSelectableFocusable(focusAnchor))
            {
                selectable = focusAnchor;
                return true;
            }

            Selectable[] selectables = GetComponentsInChildren<Selectable>(true);
            for (int i = 0; i < selectables.Length; i++)
            {
                Selectable candidate = selectables[i];
                if (candidate == focusAnchor)
                {
                    continue;
                }

                if (IsSelectableFocusable(candidate))
                {
                    selectable = candidate;
                    return true;
                }
            }

            selectable = null;
            return false;
        }

        private static bool IsSelectableFocusable(Selectable selectable)
        {
            return selectable != null &&
                   selectable.IsActive() &&
                   selectable.IsInteractable();
        }

        private static bool RequiresSelection(ItemInteractionFlags interactionFlags)
        {
            const ItemInteractionFlags selectionFlags =
                ItemInteractionFlags.Select |
                ItemInteractionFlags.Deselect |
                ItemInteractionFlags.Move |
                ItemInteractionFlags.Submit |
                ItemInteractionFlags.Cancel;

            return (interactionFlags & selectionFlags) != 0;
        }

        [System.Diagnostics.Conditional("INPUTSYSTEM_SUPPORT")]
        private void InvalidateNavigationScope()
        {
#if INPUTSYSTEM_SUPPORT && UX_NAVIGATION
            var scope = GetComponentInParent<UnityEngine.UI.UXNavigationScope>(true);
            scope?.InvalidateSelectableCache();
#endif
        }
    }
}