import { EventEmitter } from "events";
import { Token, Comment } from "./Token";
import { BrsError } from "../Error";
/** The results of a Lexer's scanning pass. */
interface ScanResults {
    /** The tokens produced by the Lexer. */
    tokens: Token[];
    /** The comments produced by the Lexer. */
    comments: Comment[];
    /** The errors encountered by the Lexer. */
    errors: BrsError[];
}
export declare class Lexer {
    /** Allows consumers to observe errors as they're detected. */
    readonly events: EventEmitter<[never]>;
    /**
     * A convenience function, equivalent to `new Lexer().scan(toScan)`, that converts a string
     * containing BrightScript code to an array of `Token` objects that will later be used to build
     * an abstract syntax tree.
     *
     * @param toScan the BrightScript code to convert into tokens
     * @param filename the name of the file to be scanned
     * @returns an object containing an array of `errors` and an array of `tokens` to be passed to a parser.
     */
    static scan(toScan: string, filename?: string): ScanResults;
    /**
     * Convenience function to subscribe to the `err` events emitted by `lexer.events`.
     * @param errorHandler the function to call for every Lexer error emitted after subscribing
     * @returns an object with a `dispose` function, used to unsubscribe from errors
     */
    onError(errorHandler: (err: BrsError) => void): {
        dispose: () => void;
    };
    /**
     * Convenience function to subscribe to a single `err` event emitted by `lexer.events`.
     * @param errorHandler the function to call for the first Lexer error emitted after subscribing
     */
    onErrorOnce(errorHandler: (err: BrsError) => void): void;
    /**
     * Converts a string containing BrightScript code to an array of `Token` objects that will
     * later be used to build an abstract syntax tree.
     *
     * @param toScan the BrightScript code to convert into tokens
     * @param filename the name of the file to be scanned
     * @returns an object containing an array of `errors` and an array of `tokens` to be passed to a parser.
     */
    scan(toScan: string, filename: string): ScanResults;
}
export {};