using System;
using UnityEngine;
using UnityEngine.EventSystems;

namespace BriarQueen.UI.Menus.Components
{
    public class AnimatedSelectionButtonGroup : MonoBehaviour
    {
        [Header("Buttons")]
        [SerializeField]
        private AnimatedSelectionButton[] _buttons = Array.Empty<AnimatedSelectionButton>();

        [SerializeField]
        private int _defaultSelectedIndex;

        [Header("Selection")]
        [SerializeField]
        private bool _selectDefaultOnEnable = true;

        [SerializeField]
        private bool _syncEventSystemSelection = true;

        public AnimatedSelectionButton Current       { get; private set; }
        public AnimatedSelectionButton CurrentHovered { get; private set; }

        private void Reset()
        {
            _buttons = GetComponentsInChildren<AnimatedSelectionButton>(true);
        }

        private void OnEnable()
        {
            BindButtons();

            if (_selectDefaultOnEnable)
                SelectIndex(_defaultSelectedIndex, true);
        }

        private void OnDisable()
        {
            UnbindButtons();
            CurrentHovered = null;
        }

        public void SelectIndex(int index, bool instant = false)
        {
            if (_buttons == null || _buttons.Length == 0) return;
            SelectButton(_buttons[Mathf.Clamp(index, 0, _buttons.Length - 1)], instant);
        }

        public void SelectButton(AnimatedSelectionButton selectedButton, bool instant = false)
        {
            if (selectedButton == null) return;
            if (Current == selectedButton && !instant) return;

            Current = selectedButton;

            RefreshAllButtonStates(instant);
            SyncEventSystemSelection(selectedButton);
        }

        // ── Internal ──────────────────────────────────────────────────

        private void RefreshAllButtonStates(bool instant = false)
        {
            if (_buttons == null) return;

            foreach (var button in _buttons)
            {
                if (button == null) continue;

                // A button shows its highlight if it is selected OR it is the
                // hovered button AND no other button is being hovered that would
                // take visual priority. Selected button highlight only shows when
                // nothing is hovered, or when it itself is hovered.
                var isSelected = button == Current;
                var isHovered  = button == CurrentHovered;

                var showHighlight = isSelected
                    ? CurrentHovered == null || isHovered   // selected: show unless something else is hovered
                    : isHovered;                             // unselected: show only if hovered

                button.SetHighlight(showHighlight, instant);
                button.SetSelectedState(isSelected);
            }
        }

        private void HandleSelectionRequested(AnimatedSelectionButton selectedButton)
        {
            SelectButton(selectedButton);
        }

        private void HandleHoverEntered(AnimatedSelectionButton button)
        {
            CurrentHovered = button;
            RefreshAllButtonStates();
        }

        private void HandleHoverExited(AnimatedSelectionButton button)
        {
            if (CurrentHovered == button)
                CurrentHovered = null;

            RefreshAllButtonStates();
        }

        private void BindButtons()
        {
            if (_buttons == null) return;

            foreach (var button in _buttons)
            {
                if (button == null) continue;
                button.SelectionRequested += HandleSelectionRequested;
                button.HoverEntered       += HandleHoverEntered;
                button.HoverExited        += HandleHoverExited;
            }
        }

        private void UnbindButtons()
        {
            if (_buttons == null) return;

            foreach (var button in _buttons)
            {
                if (button == null) continue;
                button.SelectionRequested -= HandleSelectionRequested;
                button.HoverEntered       -= HandleHoverEntered;
                button.HoverExited        -= HandleHoverExited;
            }
        }

        private void SyncEventSystemSelection(AnimatedSelectionButton selectedButton)
        {
            if (!_syncEventSystemSelection || selectedButton.Button == null || EventSystem.current == null)
                return;

            var selectedGameObject = selectedButton.Button.gameObject;
            if (EventSystem.current.currentSelectedGameObject == selectedGameObject) return;

            EventSystem.current.SetSelectedGameObject(selectedGameObject);
        }
    }
}