using TMPro;
using UnityEngine;
using UnityEngine.EventSystems;
using UnityEngine.UI;
using System;

namespace BriarQueen.UI.Menus.Components
{
    [RequireComponent(typeof(Button))]
    public class UnderlineButton : MonoBehaviour,
        IPointerEnterHandler,
        IPointerExitHandler,
        IPointerClickHandler,
        ISelectHandler,
        IDeselectHandler
    {
        [Header("References")]
        [SerializeField] private TextMeshProUGUI _label;

        private Button              _button;
        private UnderlineButtonGroup _group;
        private bool                _isHovered;

        public event Action<UnderlineButton> SelectionRequested;
        public event Action<UnderlineButton> HoverEntered;
        public event Action<UnderlineButton> HoverExited;

        public bool IsSelected { get; private set; }

        // True when this button is registered with a group
        public bool IsGrouped => _group != null;

        private void Awake()
        {
            _button = GetComponent<Button>();
            SetUnderline(false);
        }

        private void OnDisable()
        {
            _isHovered = false;
            SetUnderline(false);
        }

        // ── Group registration ────────────────────────────────────────

        /// <summary>Called by UnderlineButtonGroup when this button is bound.</summary>
        internal void RegisterGroup(UnderlineButtonGroup group)
        {
            _group = group;
        }

        /// <summary>Called by UnderlineButtonGroup when this button is unbound.</summary>
        internal void UnregisterGroup()
        {
            _group = null;
        }

        // ── Pointer / Selection events ────────────────────────────────

        public void OnPointerEnter(PointerEventData eventData)
        {
            if (_button != null && !_button.interactable) return;

            _isHovered = true;

            if (IsGrouped)
                HoverEntered?.Invoke(this);
            else
                RefreshStandaloneState();
        }

        public void OnPointerExit(PointerEventData eventData)
        {
            _isHovered = false;

            if (IsGrouped)
                HoverExited?.Invoke(this);
            else
                RefreshStandaloneState();
        }

        public void OnPointerClick(PointerEventData eventData)
        {
            if (_button != null && !_button.interactable) return;
            SelectionRequested?.Invoke(this);
        }

        public void OnSelect(BaseEventData eventData)
        {
            if (_button != null && !_button.interactable) return;

            _isHovered = true;

            if (IsGrouped)
            {
                HoverEntered?.Invoke(this);
                SelectionRequested?.Invoke(this);
            }
            else
            {
                IsSelected = true;
                RefreshStandaloneState();
            }
        }

        public void OnDeselect(BaseEventData eventData)
        {
            _isHovered = false;

            if (IsGrouped)
                HoverExited?.Invoke(this);
            else
            {
                IsSelected = false;
                RefreshStandaloneState();
            }
        }

        // ── Public API ────────────────────────────────────────────────

        /// <summary>Called by the group to update logical selected state.</summary>
        public void SetSelectedState(bool selected)
        {
            IsSelected = selected;
        }

        /// <summary>Called by the group to drive the underline visual directly.</summary>
        public void SetUnderline(bool underlined)
        {
            if (_label == null) return;

            if (underlined)
                _label.fontStyle |= FontStyles.Underline;
            else
                _label.fontStyle &= ~FontStyles.Underline;
        }

        public GameObject GetSelectableGameObject() => gameObject;

        // ── Standalone logic ──────────────────────────────────────────

        /// <summary>
        /// Used when not in a group — the button manages its own
        /// underline based on hover and selected state directly.
        /// </summary>
        private void RefreshStandaloneState()
        {
            if (_button != null && !_button.interactable)
            {
                SetUnderline(false);
                return;
            }

            SetUnderline(IsSelected || _isHovered);
        }
    }
}