/**
 * MetricsStore — SQLite-backed metrics storage (STORY-019)
 *
 * Provides record()/query()/cleanup() for operational metrics.
 * Singleton per database path; uses WAL mode for concurrent reads.
 */
export interface MetricRecord {
    name: string;
    value: number;
    labels?: Record<string, string>;
    timestamp?: number;
}
export interface MetricRow {
    id: number;
    name: string;
    value: number;
    labels: string | null;
    timestamp: number;
}
export interface MetricQueryOptions {
    name: string;
    startTs?: number;
    endTs?: number;
    labels?: Record<string, string>;
    limit?: number;
}
export interface MetricAggregation {
    name: string;
    count: number;
    sum: number;
    avg: number;
    min: number;
    max: number;
}
export declare class MetricsStore {
    private static instances;
    private db;
    private insertStmt;
    private constructor();
    static getInstance(dbPath: string): MetricsStore;
    /** For testing: reset all singleton instances */
    static resetInstances(): void;
    record(metric: MetricRecord): void;
    recordBatch(metrics: MetricRecord[]): void;
    query(options: MetricQueryOptions): MetricRow[];
    aggregate(name: string, startTs?: number, endTs?: number): MetricAggregation | null;
    cleanup(olderThanMs: number): number;
    count(name?: string): number;
    countSince(startTs: number): number;
    close(): void;
}
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