import { opentelemetry } from './opentelemetry';

/**
 * @see https://prometheus.io/docs/concepts/data_model/#metric-names-and-labels
 */
const METRIC_REGEXP = new RegExp(
  `^${process.env.TELEMETRY_METRIC_REGEXP || '[a-zA-Z_:][a-zA-Z0-9_:]*'}$`,
);

const meters = new Map<string, opentelemetry.api.Meter>();
const counters = new Map<string, opentelemetry.api.Counter>();

let defaultMeter: opentelemetry.api.Meter | null = null;

export function getDefaultMeterName(name?: string): string {
  return (
    name ??
    process.env.OTEL_SERVICE_NAME ??
    process.env.TELEMETRY_SERVICE_NAME ??
    'service'
  );
}

export function isValidMetric(metric: string): boolean {
  return METRIC_REGEXP.test(metric);
}

export function hasMeter(name?: string) {
  return meters.has(getDefaultMeterName(name));
}

/**
 * @deprecated Avoid manipulating the meter directly. Prefer
 * using metrics.createCounter() or metrics.createHistogram()
 */
export function getMeter(
  name?: string,
  version?: string,
  options?: opentelemetry.api.MeterOptions,
): opentelemetry.api.Meter {
  const _name = getDefaultMeterName(name);
  if (meters.has(_name)) {
    return meters.get(_name)!;
  }

  const meter = opentelemetry.api.metrics.getMeter(_name, version, options);
  meters.set(_name, meter);

  if (defaultMeter === null) {
    defaultMeter = meter;
  }

  return meter;
}

/**
 * @deprecated Prefer using metrics.createCounter()
 */
export function getMetricCounter(
  metric: string,
  options?: opentelemetry.api.MetricOptions,
): opentelemetry.api.Counter {
  if (counters.has(metric)) {
    return counters.get(metric)!;
  }

  const counter = defaultMeter!.createCounter(metric, options);

  counters.set(metric, counter);

  return counter;
}

/**
 * @deprecated Prefer using metrics.metric()
 */
export function metric(
  metric: string,
  context: Record<string, string | number | boolean> = {},
  options: opentelemetry.api.MetricOptions = {},
  increment = 1,
  meterName = getDefaultMeterName(),
) {
  if (hasMeter(meterName) === false) {
    getMeter();
  }

  if (isValidMetric(metric) === false) {
    throw new Error('Invalid metric format');
  }

  return getMetricCounter(metric, options).add(increment, context);
}