export interface IMetrics {
    nodes?: Array<{
        node: string;
        timestamp: number;
    }>;
    compiler?: string;
    compilerVersion?: string;
    [key: string]: any;
}
/**
 * Push event node to metrics.
 *
 * Side-effected, shall mutate the `nodes` field in `metrics` object.
 * @param metrics
 * @param event
 */
export declare function addNodeToMetrics(metrics: IMetrics, event: string): void;
/**
 * Add field with to metrics.
 *
 * Side-effected, shall mutate the `metrics` object.
 * @param metrics
 * @param field
 * @param value
 */
export declare function addFieldToMetrics(metrics: IMetrics, field: string, value: any): void;
/**
 * Merge a list of metrics, return a new metric.
 *
 * Non-side-effected.
 * @param metrics
 * @returns
 */
export declare function mergeMetrics(...metrics: IMetrics[]): IMetrics;
/**
 * Abstract for {@link IMetrics}
 */
export declare class Metrics {
    nodes: IMetrics['nodes'];
    tags: Exclude<IMetrics, 'nodes'>;
    /**
     * Add node to {@link nodes}
     * @param event
     * @param timestamp
     */
    addNode(event: string, timestamp?: number): this;
    /**
     * Add node to {@link tags}
     * @param field
     * @param value
     */
    updateField(field: string, value: keyof Exclude<IMetrics, 'nodes'>): this;
    /**
     * Merge metrics, the order matters
     */
    merge(...others: IMetrics[]): this;
    /**
     * Settle the metrics
     * @param clear whether to reset the metrics to empty.
     * @returns
     */
    settle(clear?: boolean): IMetrics;
    /**
     * Clear the metrics.
     */
    clear(): this;
}