// src/services/voiceDiag/checks/wan/wanJitter.js
//
// Per-path WAN jitter (LQM inter-packet arrival variation, ms) vs
// voice-quality references:
//   - <= 30ms : good (jitter buffer handles it cleanly)
//   - 30-50ms : warn (audible choppiness on longer calls)
//   - > 50ms  : error (jitter buffer starts dropping packets;
//               garbled audio)
//
// Both thresholds are env-configurable via WAN_STANDARD_JITTER_*.

import {
  maybeSkippedByKillSwitch,
  getLinks,
  getJitterWarnMs,
  getJitterErrorMs,
  evaluatePerLinkMetric,
} from './_helpers.js';

export const WAN_JITTER_STANDARDS = Object.freeze({
  maxWarnMs: 30,
  maxErrorMs: 50,
  unit: 'ms',
  reference: 'RFC 3550 jitter buffer sizing',
});

export const wanJitterCheck = {
  id: 'wanJitter',
  label: 'SD-WAN Jitter (per path)',
  requires: ['sdwanSite'],
  scope: null,
  standards: WAN_JITTER_STANDARDS,

  async run(ctx) {
    const skip = maybeSkippedByKillSwitch(wanJitterCheck);
    if (skip) return skip;

    const warnThresh = getJitterWarnMs();
    const errorThresh = getJitterErrorMs();
    return evaluatePerLinkMetric({
      links: getLinks(ctx),
      metricKey: 'jitterMs',
      label: 'jitter',
      unit: 'ms',
      warnThresh,
      errorThresh,
      lowIsBad: false,
      standardLabel: `warn > ${warnThresh}ms, error > ${errorThresh}ms`,
    });
  },
};