/**
 * CSV Formatter Stream
 *
 * True streaming CSV formatter using cross-platform stream module.
 * Works identically in both Node.js and Browser environments.
 */
import { Transform } from "../../stream/index.js";
import type { CsvFormatOptions, Row } from "../types.js";
/**
 * Transform stream that formats rows to CSV
 *
 * @example
 * ```ts
 * const formatter = new CsvFormatterStream({ headers: ['name', 'age'] });
 * formatter.pipe(writable);
 * formatter.write(['Alice', 30]);
 * formatter.write(['Bob', 25]);
 * formatter.end();
 * ```
 */
export declare class CsvFormatterStream extends Transform {
    private options;
    /** Unified format configuration (shared with batch formatter) */
    private formatConfig;
    private headerWritten;
    /** Keys to access data from source objects */
    private keys;
    /** Headers to write to output (may differ from keys) */
    private displayHeaders;
    /** Index of source row (before filtering), passed to transform.row */
    private sourceRowIndex;
    /** Index of output data row (after filtering, excludes header), used for ctx.index */
    private outputRowIndex;
    /** Pre-allocated options object to avoid per-row allocation in streaming */
    private rowOptions;
    push: (chunk: string | null) => boolean;
    write: {
        (chunk: Row, callback?: (error?: Error | null) => void): boolean;
        (chunk: Row, encoding?: string, callback?: (error?: Error | null) => void): boolean;
    };
    constructor(options?: CsvFormatOptions);
    /**
     * Auto-detect keys/headers from a row (object or RowHashArray)
     */
    private detectHeadersFromRow;
    _transform(chunk: Row, _encoding: string, callback: (error?: Error | null, data?: string) => void): void;
    _destroy(error: Error | null, callback: (error: Error | null) => void): void;
    _flush(callback: (error?: Error | null) => void): void;
    private formatAndPush;
    private formatRow;
}
/**
 * Create formatter stream factory
 */
export declare function createCsvFormatterStream(options?: CsvFormatOptions): CsvFormatterStream;