using UnityEngine;
using UnityEngine.EventSystems;

namespace AlicizaX.UI
{
    public sealed class RecyclerNavigationController
    {
        private readonly RecyclerView recyclerView;

        public RecyclerNavigationController(RecyclerView recyclerView)
        {
            this.recyclerView = recyclerView;
        }

        public bool TryMove(ViewHolder currentHolder, MoveDirection direction, RecyclerNavigationOptions options)
        {
            if (recyclerView == null ||
                recyclerView.RecyclerViewAdapter == null ||
                currentHolder == null)
            {
                return false;
            }

            int itemCount = recyclerView.RecyclerViewAdapter.GetItemCount();
            int realCount = recyclerView.RecyclerViewAdapter.GetRealCount();
            if (itemCount <= 0 || realCount <= 0)
            {
                return false;
            }

            int step = GetStep(direction);
            if (step == 0)
            {
                return false;
            }

            bool isLoopSource = itemCount != realCount;
            bool allowWrap = isLoopSource && options.Wrap;
            int nextLayoutIndex = currentHolder.Index + step;
            if (allowWrap)
            {
                nextLayoutIndex = WrapIndex(nextLayoutIndex, realCount);
            }
            else
            {
                nextLayoutIndex = Mathf.Clamp(nextLayoutIndex, 0, itemCount - 1);
            }

            if (!allowWrap && nextLayoutIndex == currentHolder.Index)
            {
                return false;
            }

            ScrollAlignment alignment = ResolveAlignment(direction, options.Alignment);
            return recyclerView.TryFocusIndex(nextLayoutIndex, options.SmoothScroll, alignment);
        }

        private int GetStep(MoveDirection direction)
        {
            int unit = Mathf.Max(1, recyclerView.LayoutManager != null ? recyclerView.LayoutManager.Unit : 1);
            bool vertical = recyclerView.Direction == Direction.Vertical;

            return direction switch
            {
                MoveDirection.Left => vertical ? -1 : -unit,
                MoveDirection.Right => vertical ? 1 : unit,
                MoveDirection.Up => vertical ? -unit : -1,
                MoveDirection.Down => vertical ? unit : 1,
                _ => 0
            };
        }

        private static int WrapIndex(int index, int count)
        {
            int wrapped = index % count;
            return wrapped < 0 ? wrapped + count : wrapped;
        }

        private ScrollAlignment ResolveAlignment(MoveDirection direction, ScrollAlignment fallback)
        {
            if (recyclerView == null || recyclerView.LayoutManager == null)
            {
                return fallback;
            }

            bool vertical = recyclerView.Direction == Direction.Vertical;
            return direction switch
            {
                MoveDirection.Down when vertical => ScrollAlignment.End,
                MoveDirection.Up when vertical => ScrollAlignment.Start,
                MoveDirection.Right when !vertical => ScrollAlignment.End,
                MoveDirection.Left when !vertical => ScrollAlignment.Start,
                _ => fallback
            };
        }
    }
}