using System.ComponentModel;
using System.Reflection;
using System.Windows;
using System.Windows.Controls.Primitives;
using System.Windows.Markup;

namespace ShrlAlgo.Toolkit.Mvvm.Markup
{
    /// <summary>
    /// 枚举类作为数据源
    /// </summary>
    public class EnumSourceExtension : MarkupExtension
    {
        private Type enumType;
        public bool BindToDescription { get; set; } = false;
        public Type EnumType
        {
            get { return enumType; }
            set
            {
                if (value != enumType)
                {
                    if (null != value)
                    {
                        var enumType = Nullable.GetUnderlyingType(value) ?? value;
                        if (!enumType.IsEnum)
                        {
                            throw new ArgumentException("类型必须是枚举类型");
                        }
                    }
                    enumType = value;
                }
            }
        }
        /// <summary>
        /// 在ResouceDictionary中声明
        /// </summary>
        /// <example><c>local:EnumSourceExtension x:Key="EnumBindingSource" EnumType="{x:Type local:Sex}"</c></example>
        public EnumSourceExtension()
        {

        }
        /// <summary>
        /// 用Markup语法
        /// </summary>
        /// <param name="enumType"></param>
        /// <remarks>若需要绑定Description，则需设置BindToDescription为True，同时只能用SelectedValue来绑定源属性</remarks>
        /// <example><c>ItemsSource="{Binding Source={local:EnumTypeBindingSource {x:Type local:ExampleEnum}}}"</c></example>
        /// <example><c>ItemsSource="{local:EnumSource EnumType=local:ExampleEnum}" SelectedItem="{Binding ExampleEnum}"</c></example>
        public EnumSourceExtension(Type enumType) { EnumType = enumType; }

        public override object ProvideValue(IServiceProvider serviceProvider)
        {
            var pvt = (IProvideValueTarget)serviceProvider.GetService(typeof(IProvideValueTarget));

            if (pvt == null) { return null; }

            //如果为空，则返回运行时绑定的类。
            if (pvt.TargetObject is not FrameworkElement) { return this; }

            var enumValues = Enum.GetValues(enumType);
            if (BindToDescription)
            {
                var items = new List<object>();
                foreach (var enumValue in enumValues)
                {
                    var item = new
                    {
                        Value = enumValue,
                        Description = GetDescription(enumValue)
                    };
                    items.Add(item);
                }

                if (pvt.TargetObject is Selector selector)
                {
                    selector.DisplayMemberPath = "Description";
                    selector.SelectedValuePath = "Value";
                }

                return items;
            }
            return enumValues;
        }
        private static string GetDescription(object enumValue)
        {
            var fieldInfo = enumValue.GetType().GetField(enumValue.ToString());
            var descriptionAttribute = fieldInfo.GetCustomAttribute<DescriptionAttribute>();

            return descriptionAttribute?.Description ?? enumValue.ToString();
        }
    }

}