using System;
using System.Collections.Generic;
using System.Globalization;
using System.Windows;
using Prism.Commands;
using Prism.Mvvm;
using XP.Common.Localization.Enums;
using XP.Common.Localization.Interfaces;
using XP.Common.Logging.Interfaces;


namespace XP.Common.Localization.ViewModels
{
    /// <summary>
    /// 语言切换器 ViewModel | Language switcher ViewModel
    /// 提供语言选择和切换功能 | Provides language selection and switching functionality
    /// </summary>
    public class LanguageSwitcherViewModel : BindableBase
    {
        private readonly ILocalizationService _localizationService;
        private readonly ILocalizationConfig _config;
        private readonly ILoggerService _logger;
        private LanguageOption? _selectedLanguage;

        /// <summary>
        /// 选中的语言选项 | Selected language option
        /// </summary>
        public LanguageOption? SelectedLanguage
        {
            get => _selectedLanguage;
            set
            {
                if (SetProperty(ref _selectedLanguage, value))
                {
                    ApplyCommand.RaiseCanExecuteChanged();
                    UpdatePreviewTexts();
                }
            }
        }

        /// <summary>
        /// 可用语言列表 | Available languages list
        /// </summary>
        public IEnumerable<LanguageOption> AvailableLanguages { get; }

        /// <summary>
        /// 应用按钮命令 | Apply button command
        /// </summary>
        public DelegateCommand ApplyCommand { get; }

        private string _previewRestartNotice = string.Empty;
        /// <summary>
        /// 预览重启提示文本 | Preview restart notice text
        /// </summary>
        public string PreviewRestartNotice
        {
            get => _previewRestartNotice;
            set => SetProperty(ref _previewRestartNotice, value);
        }

        private string _previewApplyButtonText = string.Empty;
        /// <summary>
        /// 预览应用按钮文本 | Preview apply button text
        /// </summary>
        public string PreviewApplyButtonText
        {
            get => _previewApplyButtonText;
            set => SetProperty(ref _previewApplyButtonText, value);
        }

        /// <summary>
        /// 构造函数 | Constructor
        /// </summary>
        /// <param name="localizationService">本地化服务 | Localization service</param>
        /// <param name="config">本地化配置 | Localization configuration</param>
        /// <param name="logger">日志服务 | Logger service</param>
        public LanguageSwitcherViewModel(
            ILocalizationService localizationService,
            ILocalizationConfig config,
            ILoggerService logger)
        {
            _localizationService = localizationService ?? throw new ArgumentNullException(nameof(localizationService));
            _config = config ?? throw new ArgumentNullException(nameof(config));
            _logger = logger.ForModule<LanguageSwitcherViewModel>();

            // 初始化可用语言列表 | Initialize available languages list
            AvailableLanguages = new[]
            {
                new LanguageOption(SupportedLanguage.ZhCN, "简体中文", "🇨🇳"),
                new LanguageOption(SupportedLanguage.ZhTW, "繁體中文", "🇹🇼"),
                new LanguageOption(SupportedLanguage.EnUS, "English", "🇺🇸")
            };

            // 设置当前选中的语言 | Set currently selected language
            var currentLang = localizationService.CurrentLanguage;
            foreach (var lang in AvailableLanguages)
            {
                if (lang.Language == currentLang)
                {
                    _selectedLanguage = lang;
                    break;
                }
            }

            // 初始化命令 | Initialize commands
            ApplyCommand = new DelegateCommand(OnApply, CanApply);
            
            // 初始化预览文本 | Initialize preview texts
            UpdatePreviewTexts();
        }

        /// <summary>
        /// 更新预览文本 | Update preview texts
        /// </summary>
        private void UpdatePreviewTexts()
        {
            if (_selectedLanguage == null)
                return;

            // 获取选中语言的 CultureInfo | Get CultureInfo for selected language
            var previewCulture = GetCultureInfo(_selectedLanguage.Language);
            
            // 使用选中的语言获取本地化文本 | Get localized text using selected language
            PreviewRestartNotice = _localizationService.GetString("Settings_Language_RestartNotice", previewCulture);
            PreviewApplyButtonText = _localizationService.GetString("Button_Apply", previewCulture);
        }

        /// <summary>
        /// 判断是否可以应用 | Determine if can apply
        /// 与配置文件中已保存的语言比较 | Compare with saved language in config
        /// </summary>
        private bool CanApply()
        {
            if (_selectedLanguage == null)
                return false;

            // 获取配置文件中已保存的语言 | Get saved language from config
            var savedLanguage = _config.GetSavedLanguage() ?? _localizationService.CurrentLanguage;
            return _selectedLanguage.Language != savedLanguage;
        }

        /// <summary>
        /// 应用语言切换 | Apply language change
        /// </summary>
        private void OnApply()
        {
            if (_selectedLanguage == null)
                return;

            try
            {
                var newLanguage = _selectedLanguage.Language;
                _localizationService.SetLanguage(newLanguage);
                
                _logger.Info($"Language switched to {newLanguage}");

                // 显示重启提示对话框 | Show restart prompt dialog
                MessageBox.Show(
                    _localizationService.GetString("Settings_Language_SavedRestartRequired"),
                    _localizationService.GetString("Dialog_Notice"),
                    MessageBoxButton.OK,
                    MessageBoxImage.Information);
                
                // 更新命令状态 | Update command state
                ApplyCommand.RaiseCanExecuteChanged();
            }
            catch (Exception ex)
            {
                _logger.Error(ex, $"Failed to switch language to {_selectedLanguage.Language}");
                
                // 显示错误对话框 | Show error dialog
                var errorMsg = string.Format(
                    _localizationService.GetString("Settings_Language_SwitchFailed"),
                    ex.Message);
                MessageBox.Show(
                    errorMsg,
                    _localizationService.GetString("Dialog_Error"),
                    MessageBoxButton.OK,
                    MessageBoxImage.Error);
                
                // 恢复到之前的语言 | Restore previous language
                var currentLang = _localizationService.CurrentLanguage;
                foreach (var lang in AvailableLanguages)
                {
                    if (lang.Language == currentLang)
                    {
                        _selectedLanguage = lang;
                        RaisePropertyChanged(nameof(SelectedLanguage));
                        break;
                    }
                }
            }
        }

        /// <summary>
        /// 获取语言对应的 CultureInfo | Get CultureInfo for language
        /// </summary>
        private CultureInfo GetCultureInfo(SupportedLanguage language)
        {
            return language switch
            {
                SupportedLanguage.ZhCN => new CultureInfo("zh-CN"),
                SupportedLanguage.ZhTW => new CultureInfo("zh-TW"),
                SupportedLanguage.EnUS => new CultureInfo("en-US"),
                _ => new CultureInfo("zh-CN")
            };
        }
    }
}