I18n.h

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#pragma once
 
#include "cdc_core/Raii.h"
 
#include <cstdint>
#include <cstddef>
#include <functional>
#include <string>
#include <vector>
 
namespace cdc::ui {

struct I18nEntry {
    const char* key;   
    const char* en;    
};

struct OverlayLanguage {
    std::string code;   
    std::string name;   
};
 
class I18n {
public:
    static constexpr const char* OVERLAY_DIR = "/plugins/i18n";

    static I18n& instance();

    bool init();

    bool loadOverlay();

    void registerEnglishTable(const I18nEntry* entries, std::size_t count);

    const char* tr(const char* key) const;

    const char* overlayTr(const char* key) const;

    const std::string& getLanguageCode() const { return currentLang_; }

    bool setLanguageCode(const char* code);

    const std::vector<OverlayLanguage>& availableOverlayLanguages() const { return overlayLangs_; }

    const char* languageName(const char* code) const;

    using LanguageChangedCallback = std::function<void()>;
    void setOnLanguageChanged(LanguageChangedCallback cb) { onChanged_ = std::move(cb); }
 
private:
    I18n();
 
    void registerCoreEnglishTable();
    bool sortIfNeeded() const;
    const char* enLookup(const char* key) const;
    const char* overlayLookup(const char* key) const;
    void loadLanguageFromNvs();
    void saveLanguageToNvs();

    void scanAvailableLanguages();
    bool loadActiveOverlayFile();
 
    mutable std::vector<I18nEntry> en_;
    mutable bool                   enSorted_ = false;
 
    // Active-language overlay stored entirely in PSRAM: a packed
    // "key\0value\0..." blob plus a key-sorted reference index for binary
    // search. Keeps the (potentially large) translation table off the scarce
    // internal heap, which WiFi/BLE need for contiguous allocations.
    struct OverlayRef { const char* key; const char* value; };
    cdc::core::PsramUniquePtr<char>       overlayBlob_;
    cdc::core::PsramUniquePtr<OverlayRef> overlayRefs_;
    std::size_t                           overlayCount_ = 0;
    std::vector<OverlayLanguage>          overlayLangs_;
 
    std::string currentLang_ = "en";
 
    LanguageChangedCallback onChanged_;
};

inline const char* tr(const char* key)
{
    return I18n::instance().tr(key);
}
 
}  // namespace cdc::ui