using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Data;
using System.Windows.Markup;

namespace AntDesign.WPF.Converters;

/// <summary>
/// 构造单例的Converter的markup
/// </summary>
/// <example>
/// 示例代码：
/// <code>
/// <![CDATA[<TextBlock Text="{Binding Value, Converter={local:GenericConverterExtension Type={x:Type local:MyValueConverter}}}" />]]>
/// </code>
/// </example>
public class GenericConverterExtension : MarkupExtension
{
    public Type Type { get; set; }

    private static readonly Dictionary<Type, object> _instances = new();
    public override object ProvideValue(IServiceProvider serviceProvider)
    {
        if (Type == null || !typeof(IValueConverter).IsAssignableFrom(Type)|| !typeof(IMultiValueConverter).IsAssignableFrom(Type))
            throw new InvalidOperationException("类型必须是值转换器");

        if (!_instances.TryGetValue(Type, out var instance))
            _instances[Type] = instance = Activator.CreateInstance(Type);

        return instance;
    }
}