using System.Collections.Generic;
using UnityEngine;
using UnityEngine.Events;
using UnityEngine.EventSystems;


[DisallowMultipleComponent]
public class UXGroup : UIBehaviour
{
    [SerializeField] private bool m_AllowSwitchOff;
    [SerializeField] private List<UXButton> m_Buttons = new();

    private UXButton _current;

    public UnityEvent<UXButton> onSelectedChanged = new();

    public bool allowSwitchOff
    {
        get => m_AllowSwitchOff;
        set
        {
            m_AllowSwitchOff = value;
            ValidateGroup();
        }
    }

    protected override void Awake() => ValidateGroup();

    protected override void OnDestroy()
    {
        foreach (var btn in m_Buttons)
            if (btn)
                btn.Selected = false;
        m_Buttons.Clear();
        base.OnDestroy();
    }

    public void RegisterButton(UXButton button)
    {
        if (!button) return;
        if (m_Buttons.Contains(button)) return;
        m_Buttons.Add(button);

        if (button.Selected)
        {
            if (_current && _current != button)
                _current.Selected = false;
            _current = button;
        }

        ValidateGroup();
    }

    public void UnregisterButton(UXButton button)
    {
        if (!button) return;
        m_Buttons.Remove(button);
        if (_current == button)
            _current = null;
        button.Selected = false;
    }

    internal void NotifyButtonClicked(UXButton button)
    {
        if (!button) return;

        if (button.Selected)
        {
            if (m_AllowSwitchOff) SetSelected(null);
        }
        else
        {
            SetSelected(button);
        }
    }

    private void SetSelected(UXButton target)
    {
        var previous = _current;
        _current = null;

        foreach (var btn in m_Buttons)
        {
            bool select = (btn == target);
            if (btn.Selected != select)
                btn.Selected = select;
            if (select) _current = btn;
        }

        if (previous != _current)
            onSelectedChanged?.Invoke(_current);
    }

    private void ValidateGroup()
    {
        if (_current != null && _current.Selected) return;

        if (!m_AllowSwitchOff && m_Buttons.Count > 0)
            SetSelected(m_Buttons[0]);
    }

    public bool AnyOtherSelected(UXButton exclude)
    {
        foreach (var btn in m_Buttons)
            if (btn != exclude && btn.Selected)
                return true;
        return false;
    }

    public void SelectNext() => SelectRelative(1);
    public void SelectPrevious() => SelectRelative(-1);

    private void SelectRelative(int dir)
    {
        if (m_Buttons.Count == 0) return;
        int start = _current ? m_Buttons.IndexOf(_current) : -1;
        int next = FindNextSelectable(start, dir);
        if (next >= 0) SetSelected(m_Buttons[next]);
    }

    private int FindNextSelectable(int startIndex, int dir)
    {
        if (m_Buttons.Count == 0) return -1;
        int count = m_Buttons.Count;
        int index = (startIndex + dir + count) % count;

        for (int i = 0; i < count; i++)
        {
            var btn = m_Buttons[index];
            if (btn && btn.isActiveAndEnabled && btn.Interactable)
                return index;
            index = (index + dir + count) % count;
        }

        return -1;
    }
}