feat: implement localization support and add language settings

WeModPatcher/Core/Services/LocalizationManager.cs

@@ -0,0 +1,150 @@
+using System;
+using System.Collections;
+using System.Collections.Generic;
+using System.Globalization;
+using System.Linq;
+using System.Threading;
+using System.Windows;
+
+namespace WeModPatcher.Core.Services
+{
+    public static class LocalizationManager
+    {
+        public static readonly List<CultureInfo> SupportedLanguages = new List<CultureInfo>
+        {
+            new CultureInfo("en-US"),
+            new CultureInfo("zh-CN"),
+            new CultureInfo("de-DE"),
+            new CultureInfo("fr-FR"),
+            new CultureInfo("es-ES"),
+            new CultureInfo("it-IT"),
+            new CultureInfo("pt-BR"),
+            new CultureInfo("pl-PL"),
+            new CultureInfo("ru-RU"),
+            new CultureInfo("uk-UA"),
+            new CultureInfo("ja-JP"),
+            new CultureInfo("tr-TR")
+        };
+
+        private static CultureInfo _currentLanguage;
+        private static ResourceDictionary _englishBaseDictionary;
+
+        public static CultureInfo CurrentLanguage
+        {
+            get => _currentLanguage;
+            set => SetLanguage(value);
+        }
+
+        public static void Initialize()
+        {
+            // Load English as the base fallback dictionary
+            _englishBaseDictionary = new ResourceDictionary
+            {
+                Source = new Uri("Locale/lang.en-US.xaml", UriKind.Relative)
+            };
+
+            // Try to load saved language preference
+            var savedLanguage = SettingsManager.LoadSettings()?.Language;
+            CultureInfo targetCulture = null;
+
+            if (!string.IsNullOrEmpty(savedLanguage))
+            {
+                targetCulture = SupportedLanguages.FirstOrDefault(c => c.Name == savedLanguage);
+            }
+
+            if (targetCulture == null)
+            {
+                // Fall back to system culture detection
+                var systemCulture = Thread.CurrentThread.CurrentUICulture;
+                targetCulture = SupportedLanguages.FirstOrDefault(c => 
+                    c.Name == systemCulture.Name || 
+                    c.TwoLetterISOLanguageName == systemCulture.TwoLetterISOLanguageName);
+            }
+            
+            SetLanguage(targetCulture ?? SupportedLanguages[0], saveSettings: false);
+        }
+
+        private static void SetLanguage(CultureInfo culture, bool saveSettings = true)
+        {
+            if (culture == null)
+                throw new ArgumentNullException(nameof(culture));
+
+            if (Equals(culture, _currentLanguage))
+                return;
+
+            var supportedCulture = SupportedLanguages.FirstOrDefault(c => c.Name == culture.Name);
+            if (supportedCulture == null)
+            {
+                supportedCulture = SupportedLanguages[0]; // Default to English
+            }
+
+            _currentLanguage = supportedCulture;
+            Thread.CurrentThread.CurrentUICulture = supportedCulture;
+
+            // Create the locale dictionary with English as base for fallback
+            var localeDict = new ResourceDictionary();
+            
+            // First, add English base dictionary for fallback
+            if (_englishBaseDictionary != null && supportedCulture.Name != SupportedLanguages[0].Name)
+            {
+                foreach (var key in _englishBaseDictionary.Keys)
+                {
+                    localeDict[key] = _englishBaseDictionary[key];
+                }
+            }
+
+            // Then overlay with the selected language (will override English keys)
+            var targetDict = new ResourceDictionary
+            {
+                Source = new Uri($"Locale/lang.{supportedCulture.Name}.xaml", UriKind.Relative)
+            };
+            
+            foreach (DictionaryEntry entry in targetDict)
+            {
+                localeDict[entry.Key] = targetDict[entry.Key];
+            }
+
+            // Find and replace the old locale dictionary
+            var oldDict = Application.Current.Resources.MergedDictionaries
+                .FirstOrDefault(d => d.Source != null && d.Source.OriginalString.StartsWith("Locale/lang."));
+
+            if (oldDict != null)
+            {
+                var index = Application.Current.Resources.MergedDictionaries.IndexOf(oldDict);
+                Application.Current.Resources.MergedDictionaries.Remove(oldDict);
+                Application.Current.Resources.MergedDictionaries.Insert(index, localeDict);
+            }
+            else
+            {
+                Application.Current.Resources.MergedDictionaries.Add(localeDict);
+            }
+            
+            if (saveSettings)
+            {
+                SettingsManager.SaveSettings(new AppSettings { Language = supportedCulture.Name });
+            }
+        }
+
+        public static string GetLanguageDisplayName(CultureInfo culture)
+        {
+            try
+            {
+                var dict = new ResourceDictionary
+                {
+                    Source = new Uri($"Locale/lang.{culture.Name}.xaml", UriKind.Relative)
+                };
+                
+                if (dict.Contains("language_display_name"))
+                {
+                    return dict["language_display_name"] as string ?? culture.NativeName;
+                }
+            }
+            catch
+            {
+                // Fallback to native name if loading fails
+            }
+            
+            return culture.NativeName;
+        }
+    }
+}