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

namespace ShrlAlgoToolkit.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);
        }
    }
}