// src/services/voiceDiag/checks/wan/wanAppRtpMos.js
//
// Per-application audio MOS — measured on ACTUAL RTP voice traffic
// via Prisma DPI, not on synthetic link probes. Metric name on the
// v2.6 monitor/metrics endpoint is `AppAudioMos` (unit: count),
// requires filter.direction="Ingress".
//
// Which app is measured depends on the tenant's configured voice
// application (PRISMA_APP_ID_VOICE env). Common choices are
// `Webex_Calling_RTP` (recommended for Webex Calling shops — the
// Webex-specific DPI signature excludes noise from other UDP
// traffic that pollutes generic RTP), `rtp-base`, `MS_Teams_RTP`,
// etc. The check is app-agnostic; the app name is threaded through
// the message + details so operators know which app was graded.
//
// Grades against the WORST-window MOS in the series. A store that
// averages 4.0 MOS over 24h but dipped to 1.85 for several 5-min
// windows had unusable calls in those windows — the average smooths
// that away and the LQM link-probe average smooths it away twice.
// This check is the escape hatch for that failure mode.
//
// Skipped when the voice-app env is not configured (feature-gated
// to keep the extra Prisma API load opt-in per tenant).

import {
  maybeSkippedByKillSwitch,
  getAppAudio,
  evaluateAppAudioMetric,
  getAppMosWarn,
  getAppMosError,
} from './_helpers.js';

export const WAN_APP_RTP_MOS_STANDARDS = Object.freeze({
  minWarnMos:  4.0,
  minErrorMos: 3.5,
  unit: 'count',
  reference: 'ITU-T P.800 (MOS)',
  gradeAgainst: 'worst-window',
});

export const wanAppRtpMosCheck = {
  id: 'wanAppRtpMos',
  label: 'SD-WAN Voice Traffic MOS (worst window)',
  requires: ['sdwanSite'],
  scope: null,
  standards: WAN_APP_RTP_MOS_STANDARDS,

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

    const audio = getAppAudio(ctx, 'mos');
    const warnThresh  = getAppMosWarn();
    const errorThresh = getAppMosError();
    return evaluateAppAudioMetric({
      audio,
      label: 'MOS',
      unit: '',
      warnThresh,
      errorThresh,
      lowIsBad: true,
      standardLabel: `warn < ${warnThresh}, error < ${errorThresh}`,
    });
  },
};