/**
 * Structured Logger for Rebase Backend
 *
 * Outputs JSON lines when `NODE_ENV=production`, human-readable prefixed
 * lines otherwise.  Designed to work with Google Cloud Logging severity levels.
 *
 * Usage:
 *   import { logger } from "./utils/logger";
 *   logger.info("Server started", { port: 3001 });
 *   logger.error("Request failed", { path: "/api/test", error: err });
 */
export type LogLevel = "debug" | "info" | "warn" | "error";
export interface LogEntry {
    severity: string;
    message: string;
    timestamp: string;
    [key: string]: unknown;
}
export interface Logger {
    debug(message: string, data?: Record<string, unknown>): void;
    info(message: string, data?: Record<string, unknown>): void;
    warn(message: string, data?: Record<string, unknown>): void;
    error(message: string, data?: Record<string, unknown>): void;
    child(defaultFields: Record<string, unknown>): Logger;
}
/**
 * Singleton logger instance.
 * In production: emits JSON lines with `severity`, `message`, `timestamp`.
 * In development: emits human-readable prefixed lines.
 */
export declare const logger: Logger;