import * as plugins from '../plugins.js';
/**
 * Base decoder class for all invoice XML formats.
 * Provides common functionality and interfaces for different format decoders.
 */
export declare abstract class BaseDecoder {
    protected xmlString: string;
    constructor(xmlString: string);
    /**
     * Abstract method that each format-specific decoder must implement.
     * Converts XML into a structured letter object based on the XML format.
     */
    abstract getLetterData(): Promise<plugins.tsclass.business.ILetter>;
    /**
     * Creates a default letter object with minimal data.
     * Used as a fallback when parsing fails.
     */
    protected createDefaultLetter(): plugins.tsclass.business.ILetter;
}