using System;
using System.Collections.Generic;
using System.Linq;
using MelonLoader;
using UnityEngine.UIElements;

namespace ADOFAIRenderer.Data
{
    /// <summary>
    /// Binds a UI Toolkit <see cref="DropdownField"/> to an enum type.
    /// Populates choices from enum names and provides typed access to the selected value.
    /// </summary>
    /// <typeparam name="T">The enum type to bind.</typeparam>
    public class EnumDropdownBinder<T> where T : struct, Enum
    {
        private readonly DropdownField? _dropdown;
        private readonly List<T> _values;
        private Action<T>? _onValueChanged;

        /// <summary>
        /// The currently selected enum value.
        /// </summary>
        public T Value => _dropdown != null && _dropdown.index >= 0 && _dropdown.index < _values.Count
            ? _values[_dropdown.index]
            : default;

        /// <summary>
        /// Queries a <see cref="DropdownField"/> by name from the root VisualElement,
        /// populates it with enum names, and selects the default value.
        /// </summary>
        /// <param name="rootVisualElement">The root VisualElement loaded from the UXML bundle.</param>
        /// <param name="fieldName">The name of the DropdownField in the UXML.</param>
        /// <param name="defaultValue">The initial selected value. Defaults to the first enum member.</param>
        public EnumDropdownBinder(VisualElement rootVisualElement, string fieldName, T? defaultValue = null)
        {
            _values = Enum.GetValues(typeof(T)).Cast<T>().ToList();

            _dropdown = rootVisualElement.Q<DropdownField>(fieldName);
            if (_dropdown == null)
            {
                Melon<RenderMod>.Logger.Error(
                    $"DropdownField '{fieldName}'을(를) 찾을 수 없습니다.");
                return;
            }

            _dropdown.choices = _values.Select(v => v.ToString()).ToList();

            // Register the callback BEFORE setting index so the initial selection fires it too
            _dropdown.RegisterValueChangedCallback(_ =>
            {
                _onValueChanged?.Invoke(Value);
            });

            var initial = defaultValue ?? _values[0];
            _dropdown.index = _values.IndexOf(initial);
        }

        /// <summary>
        /// Registers a callback that fires when the selection changes, providing the new enum value.
        /// </summary>
        public void OnValueChanged(Action<T> callback)
        {
            _onValueChanged = callback;

            // Fire immediately with current value so the caller gets the initial state
            if (_dropdown != null)
            {
                callback(Value);
            }
        }
    }
}