import { EventEmitter } from 'events';
export declare const NOT_PREDEFINED_VALUE = "NOT_PREDEFINED_VALUE";
export type TNOT_PREDEFINED_VALUE = typeof NOT_PREDEFINED_VALUE;
export type TMetricsConfig<TMetricsTypes extends string, TLabelsTypes extends Record<string, readonly string[] | 'NOT_PREDEFINED_VALUE'>> = {
    [key in TMetricsTypes]: {
        metric: TMetricsClasses;
        labels?: Partial<TLabelsTypes>;
        help?: string;
        buckets?: number[];
        method?: 'inc' | 'dec' | 'set' | 'observe';
        name?: string;
    };
};
export type TMetricsClasses = 'Counter' | 'Histogram' | 'Gauge';
/**
 * Create instance of a EventEmitter for emitting prometheus metrics ( https://prometheus.io/ )
 *
 * This single common implementation aims to provide a common implementation
 * that all services can use.
 *
 * @param metricsConfig - configuration for all allowed AND required metrics
 * @param prefix - string prefix added to all metrics names
 *
 * -------
 *
 * Metrics configuration
 *
 * 	```typescript
 *  // allowed AND required metrics
 *	type TMetricsEvents = 'metric_counter_inc_with_label' | 'metric_counter_inc_with_label_and_value';
 *
 *	const type1Labels = ['type1_label1', 'type1_label2', 'type1_label3'] as const;
 *
 *  // allowed labels
 *	type TLabelsTypes = {
 *		type1: typeof type1Labels;
 *	};
 *
 *	let metricsConfig: TMetricsConfig<TMetricsEvents, TLabelsTypes> = {
 *		metric_counter_inc_with_label: {
 *			// metrics type (one of Counter, Gauge, Histogram)
 *			metric: Counter,
 *			help: 'metric_counter_inc help',
 *			// metrics method
 *			method: 'inc',
 *			// allowed labels
 *			labels: { type1: type1Labels },
 *			// metrics name - `key` of this configuration is used if not provided (`metric_counter_inc_with_label` in this case)
 *			name: 'some_name',
 *		},
 *	}
 *
 *  const metrics = new Metrics<TMetricsEvents, TLabelsTypes>({ metricsConfig, prefix: 'sos_test_' });
 *
 *  ```
 *
 * -------
 *
 *  Emit metrics:
 *
 *  ```typescript
 *  metrics.emit('metric_counter_inc_with_label', { type1: 'type1_label1' }, 10);
 *  metrics.emit('metric_counter_inc_with_label', { type1: 'type1_label1' });
 *  metrics.emit('metric_counter_inc_with_label', 10);
 *  ```
 */
export declare class Metrics<TMetricsTypes extends string, TLabelsTypes extends Record<string, readonly string[] | TNOT_PREDEFINED_VALUE>> extends EventEmitter {
    private metricsConfig;
    private metrics;
    private prefix?;
    constructor({ metricsConfig, prefix }: {
        metricsConfig: TMetricsConfig<TMetricsTypes, TLabelsTypes>;
        prefix?: string;
    });
    emit(eventName: TMetricsTypes, labels: {
        [key in keyof TLabelsTypes]?: TLabelsTypes[key][number];
    }, value?: number, method?: 'inc' | 'dec' | 'set' | 'observe'): boolean;
    emit(eventName: TMetricsTypes, value?: number): boolean;
    on(eventName: TMetricsTypes, listener: (labels?: Partial<Record<keyof TLabelsTypes, string>>, value?: number, method?: 'inc' | 'dec' | 'set' | 'observe') => void): this;
    private getMetricsClass;
    private registerMetrics;
    private validateLabels;
    private getMetricsMethod;
}