using System.Collections.ObjectModel;
using System.ComponentModel;
using System.Globalization;
using System.Reflection;
using System.Windows.Data;

namespace Sai.Toolkit.Mvvm.Converters;

/// <summary>
///     Description（描述特性）的枚举转换同时也是枚举源的集合
/// </summary>
public class EnumItemsSourceAndConverter : Collection<string>, IValueConverter
{
	private IDictionary<object, object> displayNameToValueMap;
	private Type type;

	private IDictionary<object, object> valueToDisplayNameMap;

	public Type Type
	{
		get => type;
		set
		{
			if (!value.IsEnum)
			{
				throw new ArgumentException("不是枚举类型", $"{value}");
			}

			type = value;
			Initialize();
		}
	}

	/// <summary>
	/// 类属性到控件属性，源到目标
	/// </summary>
	/// <param name="value"></param>
	/// <param name="targetType"></param>
	/// <param name="parameter"></param>
	/// <param name="culture"></param>
	/// <returns></returns>
	public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
	{
		//if (value != null)
		//{
		//    int n = (int)value;
		//    if (n == 0 || n == -1)
		//    {
		//        return null;
		//    }
		//}
		return value == null
			? null
			: valueToDisplayNameMap.TryGetValue(value, out var value1)
				? value1
				: null;
	}

	/// <summary>
	/// 目标到源
	/// </summary>
	/// <param name="value"></param>
	/// <param name="targetType"></param>
	/// <param name="parameter"></param>
	/// <param name="culture"></param>
	/// <returns></returns>
	public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
	{
		return value == null
			? null
			: displayNameToValueMap.TryGetValue(value, out var value1)
				? value1
				: null;
	}

	private static object GetDescription(FieldInfo fieldInfo)
	{
		var descriptionAttribute = (DescriptionAttribute)Attribute.GetCustomAttribute(fieldInfo, typeof(DescriptionAttribute));
		return descriptionAttribute != null ? descriptionAttribute.Description : fieldInfo.Name;
	}

	private void Initialize()
	{
		valueToDisplayNameMap = type.GetFields(BindingFlags.Static | BindingFlags.Public).ToDictionary(fi => fi.GetValue(null), GetDescription);
		displayNameToValueMap = valueToDisplayNameMap.ToDictionary(kvp => kvp.Value, kvp => kvp.Key);
		Clear();
		//当前converter的集合添加元素
		foreach (string name in displayNameToValueMap.Keys)
		{
			Add(name);
		}
	}
}