Localization.h

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/*
    MetaImGUI
    Copyright (C) 2026  A P Nicholson
 
    This program is free software: you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation, either version 3 of the License, or
    (at your option) any later version.
 
    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.
 
    You should have received a copy of the GNU General Public License
    along with this program.  If not, see <https://www.gnu.org/licenses/>.
*/
 
#pragma once
 
#include <map>
#include <string>
#include <unordered_map>
#include <vector>
 
namespace MetaImGUI {
 
class Localization {
public:
    static Localization& Instance();
 
    // Delete copy and move
    Localization(const Localization&) = delete;
    Localization& operator=(const Localization&) = delete;
    Localization(Localization&&) = delete;
    Localization& operator=(Localization&&) = delete;
 
    void SetLanguage(const std::string& languageCode);
 
    [[nodiscard]] std::string GetCurrentLanguage() const;
 
    [[nodiscard]] std::vector<std::string> GetAvailableLanguages() const;
 
    [[nodiscard]] std::string Tr(const std::string& key) const;
 
    void AddTranslation(const std::string& languageCode, const std::string& key, const std::string& value);
 
    bool LoadTranslations(const std::string& filepath);
 
private:
    Localization();
    ~Localization() = default;
 
    std::string m_currentLanguage;
    std::map<std::string, std::map<std::string, std::string>> m_translations; // [language][key] = value
 
    // Tr() is on the hot path — every menu item, button and tooltip looks up
    // the same handful of keys per frame. The cache resolves a key to a
    // ready-made std::string, avoiding the two-tier map lookup + English
    // fallback dance on every call. Invalidated on SetLanguage / load.
    //
    // Mutable because Tr() is logically const but caches the result of an
    // expensive lookup. Single-threaded UI usage, no synchronisation needed.
    mutable std::unordered_map<std::string, std::string> m_trCache;
};
 
} // namespace MetaImGUI
 
// Convenience macro for translation
#define TR(key) MetaImGUI::Localization::Instance().Tr(key)