using System;
using System.Configuration;
using System.Globalization;
using XP.Common.Localization.Enums;
using XP.Common.Localization.Interfaces;
using XP.Common.Logging.Interfaces;

namespace XP.Common.Localization.Configs
{
    /// <summary>
    /// 本地化配置实现 | Localization configuration implementation
    /// 使用 App.config 存储语言设置 | Uses App.config to store language settings
    /// </summary>
    public class LocalizationConfig : ILocalizationConfig
    {
        private const string LanguageKey = "Language";
        private readonly ILoggerService _logger;

        /// <summary>
        /// 构造函数 | Constructor
        /// </summary>
        /// <param name="logger">日志服务 | Logger service</param>
        public LocalizationConfig(ILoggerService logger)
        {
            _logger = (logger ?? throw new ArgumentNullException(nameof(logger))).ForModule<LocalizationConfig>();
        }

        /// <summary>
        /// 获取保存的语言设置 | Get saved language setting
        /// </summary>
        /// <returns>语言设置，如果未设置则返回 null | Language setting, or null if not set</returns>
        public SupportedLanguage? GetSavedLanguage()
        {
            try
            {
                var languageString = ConfigurationManager.AppSettings[LanguageKey];

                if (string.IsNullOrWhiteSpace(languageString))
                {
                    _logger.Info("No saved language setting found in configuration");
                    return null;
                }

                if (Enum.TryParse<SupportedLanguage>(languageString, true, out var language))
                {
                    _logger.Info($"Loaded saved language setting: {language}");
                    return language;
                }

                _logger.Warn($"Invalid language setting in configuration: '{languageString}'. Expected values: ZhCN, ZhTW, EnUS");
                return null;
            }
            catch (ConfigurationErrorsException ex)
            {
                _logger.Error(ex, "Configuration error while reading language setting");
                return null;
            }
            catch (Exception ex)
            {
                _logger.Error(ex, "Unexpected error while reading saved language setting");
                return null;
            }
        }

        /// <summary>
        /// 保存语言设置 | Save language setting
        /// </summary>
        /// <param name="language">要保存的语言 | Language to save</param>
        public void SaveLanguage(SupportedLanguage language)
        {
            try
            {
                var config = ConfigurationManager.OpenExeConfiguration(ConfigurationUserLevel.None);
                var appSettings = config.AppSettings.Settings;

                var languageValue = language.ToString();

                if (appSettings[LanguageKey] == null)
                {
                    appSettings.Add(LanguageKey, languageValue);
                    _logger.Info($"Added new language setting to configuration: {language}");
                }
                else
                {
                    appSettings[LanguageKey].Value = languageValue;
                    _logger.Info($"Updated language setting in configuration: {language}");
                }

                config.Save(ConfigurationSaveMode.Modified);
                ConfigurationManager.RefreshSection("appSettings");

                _logger.Info($"Successfully saved language setting: {language}");
            }
            catch (ConfigurationErrorsException ex)
            {
                _logger.Error(ex, $"Configuration error while saving language setting: {language}");
                throw new InvalidOperationException($"Failed to save language setting to configuration file: {ex.Message}", ex);
            }
            catch (UnauthorizedAccessException ex)
            {
                _logger.Error(ex, $"Access denied while saving language setting: {language}");
                throw new InvalidOperationException("Access denied to configuration file. Please check file permissions.", ex);
            }
            catch (Exception ex)
            {
                _logger.Error(ex, $"Unexpected error while saving language setting: {language}");
                throw new InvalidOperationException($"Failed to save language setting: {ex.Message}", ex);
            }
        }

        /// <summary>
        /// 获取系统默认语言 | Get system default language
        /// </summary>
        /// <returns>系统默认语言 | System default language</returns>
        public SupportedLanguage GetSystemDefaultLanguage()
        {
            try
            {
                var systemCulture = CultureInfo.CurrentUICulture.Name;
                _logger.Info($"Detecting system default language from culture: {systemCulture}");

                var defaultLanguage = systemCulture switch
                {
                    "zh-CN" => SupportedLanguage.ZhCN,
                    "zh-TW" or "zh-HK" or "zh-MO" => SupportedLanguage.ZhTW,
                    "en-US" or "en" => SupportedLanguage.EnUS,
                    _ when systemCulture.StartsWith("zh", StringComparison.OrdinalIgnoreCase) => SupportedLanguage.ZhCN,
                    _ when systemCulture.StartsWith("en", StringComparison.OrdinalIgnoreCase) => SupportedLanguage.EnUS,
                    _ => SupportedLanguage.ZhCN // 默认简体中文 | Default to Simplified Chinese
                };

                _logger.Info($"System default language determined: {defaultLanguage} (from culture: {systemCulture})");
                return defaultLanguage;
            }
            catch (Exception ex)
            {
                _logger.Error(ex, "Error while detecting system default language, falling back to ZhCN");
                return SupportedLanguage.ZhCN; // 默认简体中文 | Default to Simplified Chinese
            }
        }
    }
}