import type { MiddlewareHandler } from "hono";
/** Structural sink contract for request metrics. */
export interface AnalyticsEngineDatasetLike {
    writeDataPoint(point: {
        blobs?: string[];
        doubles?: number[];
        indexes?: string[];
    }): void;
}
/** Per-request db-query counter, populated by the db middleware. */
export interface RequestDbMetrics {
    queries: number;
}
export declare const DB_METRICS_CONTEXT_KEY = "__voyantDbMetrics";
export interface MetricsMiddlewareOptions {
    /** Resolve the metrics sink for a request. Returning undefined is a no-op. */
    dataset: (env: unknown) => AnalyticsEngineDatasetLike | undefined;
}
/**
 * Per-request metrics for an explicitly supplied deployment sink.
 *
 * One data point per request:
 * - blobs:   [method, routePattern, surface, cacheStatus]
 * - doubles: [durationMs, status, dbQueryCount]
 * - indexes: [routePattern]  (AE sampling key — per-route analysis)
 *
 * `writeDataPoint` is fire-and-forget and never throws into the
 * request; a missing binding short-circuits before timing overhead.
 */
export declare function metrics(options: MetricsMiddlewareOptions): MiddlewareHandler<{
    Variables: {
        [DB_METRICS_CONTEXT_KEY]?: RequestDbMetrics;
    };
}>;
/**
 * Wrap a drizzle client so top-level query-initiating calls increment
 * the request counter. Counts `select/insert/update/delete/execute/
 * transaction/query` invocations — a transaction counts as ONE (its
 * inner statements run on the tx handle, which is not wrapped). An
 * approximation by design: the goal is spotting N+1 routes and
 * subrequest-budget pressure, not exact accounting.
 */
export declare function withQueryCounting<TDb extends object>(db: TDb, counter: RequestDbMetrics): TDb;