using System;
using System.ComponentModel;
using System.Windows;
using System.Windows.Data;
using System.Windows.Markup;
using TeamAAS.Localization;

namespace TeamAAS.Localization
{
    /// <summary>
    /// XAML 标记扩展：支持动态翻译，语言切换时自动刷新
    /// 用法：Content="{loc:Translate '保存配置'}"
    /// </summary>
    [MarkupExtensionReturnType(typeof(BindingExpression))]
    public class TranslateExtension : MarkupExtension
    {
        /// <summary>
        /// 要翻译的原文（中文）
        /// </summary>
        [ConstructorArgument("key")]
        public string Key { get; set; }

        /// <summary>
        /// 可选的上下文（用于消歧义）
        /// </summary>
        public string Context { get; set; }

        /// <summary>
        /// 无参构造函数
        /// </summary>
        public TranslateExtension()
        {
        }

        /// <summary>
        /// 单参数构造函数：支持 {loc:Translate '保存配置'} 语法
        /// </summary>
        public TranslateExtension(string key)
        {
            Key = key;
        }

        public override object ProvideValue(IServiceProvider serviceProvider)
        {
            if (string.IsNullOrWhiteSpace(Key))
                return "[未设置翻译Key]";

            // 在设计时返回原文（避免设计器报错）
            if (DesignerProperties.GetIsInDesignMode(new DependencyObject()))
                return Key;

            // 创建绑定：绑定到 TranslationProxy 的 Value 属性
            // TranslationProxy 监听语言切换事件，自动更新翻译
            var proxy = new TranslationProxy(Key, Context);
            var binding = new Binding("Value")
            {
                Source = proxy,
                Mode = BindingMode.OneWay
            };

            // 如果能获取目标对象，返回绑定表达式；否则返回当前翻译
            if (serviceProvider.GetService(typeof(IProvideValueTarget)) is IProvideValueTarget target)
            {
                if (target.TargetObject is DependencyObject && target.TargetProperty is DependencyProperty)
                {
                    return binding.ProvideValue(serviceProvider);
                }
            }

            // fallback：直接返回翻译结果
            return proxy.Value;
        }
    }

    /// <summary>
    /// 翻译代理：监听语言切换事件，自动更新翻译
    /// </summary>
    internal class TranslationProxy : INotifyPropertyChanged
    {
        private readonly string _key;
        private readonly string _context;

        public TranslationProxy(string key, string context = null)
        {
            _key = key;
            _context = context;

            // 监听语言切换事件
            GlobalLocalizationManager.Instance.LanguageChanged += OnLanguageChanged;
        }

        /// <summary>
        /// 当前翻译结果
        /// </summary>
        public string Value => GlobalLocalizationManager.Instance.Translate(_key, _context);

        private void OnLanguageChanged(object sender, EventArgs e)
        {
            // 语言切换时通知绑定刷新
            PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(nameof(Value)));
        }

        public event PropertyChangedEventHandler PropertyChanged;
    }
}