import { type IdentityPlugin } from "@nifrajs/core/server";
/** Structured fields logged per request. */
export interface RequestLogFields {
    readonly method: string;
    readonly path: string;
    readonly status: number;
    /** Wall-clock duration in ms (0 if the start couldn't be paired). */
    readonly ms: number;
}
export interface LoggerOptions {
    /** Sink for each line. Default: `console.log(JSON.stringify(fields))`. Route to your own logger here. */
    readonly log?: (fields: RequestLogFields) => void;
}
/**
 * A {@link defineIdentityPlugin} plugin that logs one structured line per request - method, path,
 * status, and duration - via `onRequest`/`onResponse` (so it covers 404s and errors too). The start
 * time is paired to the request through a `WeakMap` (no per-request allocation leak). Idempotent.
 *
 * It adds no context and registers no routes, so it is type-identity: routes declared after
 * `.use(logger())` keep their types. (Under `definePlugin` they would not - see that helper's
 * FOOTGUN note.)
 */
export declare function logger(options?: LoggerOptions): IdentityPlugin;
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