using System;
using System.Windows.Markup;
using XP.Common.Localization.Interfaces;

namespace XP.Common.Localization.Extensions
{
    /// <summary>
    /// 本地化标记扩展 | Localization markup extension
    /// 用法: {loc:Localization Key=ResourceKey} | Usage: {loc:Localization Key=ResourceKey}
    /// </summary>
    [MarkupExtensionReturnType(typeof(string))]
    public class LocalizationExtension : MarkupExtension
    {
        private static ILocalizationService? _localizationService;
        private string _key = string.Empty;

        /// <summary>
        /// 资源键 | Resource key
        /// </summary>
        [ConstructorArgument("key")]
        public string Key
        {
            get => _key;
            set => _key = value;
        }

        /// <summary>
        /// 默认构造函数 | Default constructor
        /// </summary>
        public LocalizationExtension()
        {
        }

        /// <summary>
        /// 带资源键的构造函数 | Constructor with resource key
        /// </summary>
        /// <param name="key">资源键 | Resource key</param>
        public LocalizationExtension(string key)
        {
            _key = key;
        }

        /// <summary>
        /// 初始化本地化服务（由 CommonModule 调用）| Initialize localization service (called by CommonModule)
        /// </summary>
        /// <param name="localizationService">本地化服务实例 | Localization service instance</param>
        public static void Initialize(ILocalizationService localizationService)
        {
            _localizationService = localizationService;
        }

        /// <summary>
        /// 提供本地化字符串值 | Provide localized string value
        /// </summary>
        /// <param name="serviceProvider">服务提供者 | Service provider</param>
        /// <returns>本地化字符串 | Localized string</returns>
        public override object ProvideValue(IServiceProvider serviceProvider)
        {
            if (string.IsNullOrEmpty(_key))
            {
                return string.Empty;
            }

            if (_localizationService == null)
            {
                // 设计时回退 | Design-time fallback
                return $"[{_key}]";
            }

            // 直接返回当前语言的翻译字符串 | Return translated text for current language
            return _localizationService.GetString(_key);
        }
    }
}