/**
 * File-based structured logging sink for lifecycle events.
 *
 * Subscribes to the EventBus and writes all events as NDJSON to a log file,
 * providing persistent, machine-readable audit trails.
 */
import type { EventListener } from "./events.ts";
/**
 * Format a timestamp for use in log file names.
 *
 * Converts an ISO-8601 timestamp to a filesystem-safe format by replacing
 * colons with hyphens and removing fractional seconds:
 * `2025-06-15T10:32:01.123Z` -> `2025-06-15T10-32-01Z`
 */
export declare function formatTimestamp(iso: string): string;
/** Options for creating a FileLogSink. */
export type FileLogSinkOptions = {
    /** Directory to write log files into. Created if absent. */
    logDir: string;
};
/**
 * Writes lifecycle events as NDJSON to a file.
 *
 * Opens (or creates) a log file at the start of a run, subscribes to the
 * EventBus via `bus.on(sink.listener)`, and writes each event as a single
 * NDJSON line. The file is flushed and closed when `close()` is called or
 * when a `run_finished` event is received.
 */
export declare class FileLogSink {
    #private;
    constructor(options: FileLogSinkOptions);
    /** The path to the log file, once opened. */
    get filePath(): string | null;
    /** EventListener -- pass to bus.on(). */
    listener: EventListener;
    /** Flush and close the underlying file. Idempotent. */
    close(): void;
}
//# sourceMappingURL=log_sink.d.ts.map