import { Observable } from "./observer/Observable";
import { ISO639_1 } from "../domain/definitions/types/Country";
import { ILanguageService } from "../domain/definitions/interfaces/ILanguageService";
/**
 * Configuration interface for language service initialization.
 * @template LSupported The supported ISO 639-1 language codes.
 */
interface LanguageServiceConfig<LSupported extends ISO639_1> {
    /**
     * The default language code to use.
     */
    defaultLanguage: LSupported;
    /**
     * Array of supported language codes.
     */
    supportedLanguages: ReadonlyArray<LSupported>;
}
/**
 * Service for managing application language settings and locale preferences.
 * Implements singleton pattern for global language state management.
 * @template LSupported The supported ISO 639-1 language codes.
 * @implements ILanguageService
 */
export declare class LanguageService<LSupported extends ISO639_1> implements ILanguageService<LSupported> {
    /**
     * Singleton instance of the LanguageService.
     */
    private static _instance;
    /** @inheritDoc */
    readonly supportedLanguages: LSupported[];
    /** @inheritDoc */
    readonly countryCode: Observable<LSupported>;
    /**
     * Storage key for persisting language preferences.
     */
    private readonly _storeKey;
    /**
     * Default country code for the service.
     */
    private readonly _defaultCountryCode;
    /**
     * Set of supported language codes.
     */
    private readonly _supportedLanguages;
    /**
     * Creates a new LanguageService instance.
     * @param {LanguageServiceConfig<LSupported>} config Service configuration parameters.
     * @throws {EmptyLanguageConfigurationError} If no supported languages are provided.
     */
    private constructor();
    /** @inheritDoc */
    get defaultLanguage(): LSupported;
    /**
     * Retrieves the singleton instance of the language service.
     * @param {LanguageServiceConfig<LSupported>} config Initial configuration for new instances.
     * @returns {LanguageService<LSupported>} The singleton instance.
     */
    static getInstance<LSupported extends ISO639_1>(config: LanguageServiceConfig<LSupported>): LanguageService<LSupported>;
    /**
     * Adds a single language code to supported languages.
     * @param {LSupported} code The language code to add.
     */
    private _addSupportedLanguage;
    /**
     * Adds multiple language codes to supported languages.
     * @param {ReadonlyArray<LSupported>} codes Array of language codes to add.
     */
    private _addSupportedLanguages;
    /**
     * Creates and configures an Observable instance for managing language codes.
     * @returns {Observable<LSupported>} Observable instance initialized with validated browser language.
     */
    private _getCodeObservable;
    /**
     * Extracts the country code from the browser's language settings.
     * @returns {ISO639_1} The detected ISO 639-1 language code from the browser.
     */
    private _detectBrowserCountryCode;
    /**
     * Validates a country code against supported languages list.
     * @param {ISO639_1} code The country code to validate.
     * @returns {LSupported} The validated code or default country code if invalid.
     */
    private _assertValidCountryCode;
    /**
     * Updates the HTML document's lang attribute.
     * @param {ISO639_1} code The language code to set.
     */
    private _updateHtmlLang;
}
export {};