// src/services/voiceDiag/checks/wan/_helpers.js
//
// Shared kill-switch + threshold accessors for the /voicediag WAN
// bucket. Mirrors services/voiceDiag/checks/port/_helpers.js in
// intent — one file per check for the actual logic, this file for
// the common env-reading and formatting boilerplate.
//
// Threshold accessors read `process.env` at *call time* rather than
// at import time. That's what lets tests do `process.env.X = '...'`
// + await the check without needing a module cache reset. The
// downside is a couple of extra env reads per run, which is nothing
// against the network work each WAN check does (or doesn't do — the
// checks reuse data already fetched during buildContext()).

/**
 * Global kill-switch for the WAN bucket. Env
 * `WAN_STANDARD_ENABLED=false` returns a short "WAN checks are
 * currently disabled" skip result that every WAN check can return
 * verbatim. Feature-config + port-hygiene checks are intentionally
 * *not* gated by this — this only silences the SD-WAN bucket while
 * the underlying Prisma tenant is being reconfigured or the
 * integration is being validated.
 *
 * Same contract as port/_helpers.js:maybeSkippedByKillSwitch —
 * returns null when enabled (caller proceeds) or a full CheckResult
 * with `status: 'skipped'` when disabled (caller returns it as-is).
 *
 * @param {object} check the check descriptor (used for label only)
 * @returns {null | {status:'skipped', message:string, details:object, remediation:null}}
 */
export function maybeSkippedByKillSwitch(check) {
  const raw = String(process.env.WAN_STANDARD_ENABLED ?? 'true').toLowerCase().trim();
  const enabled = !(raw === 'false' || raw === '0' || raw === 'no' || raw === 'off');
  if (enabled) return null;
  return {
    status: 'skipped',
    message:
      `${check.label} skipped — WAN_STANDARD_ENABLED=false (SD-WAN checks are silenced).`,
    details: { killSwitch: 'WAN_STANDARD_ENABLED', value: raw },
    remediation: null,
  };
}

// ─── Threshold accessors ──────────────────────────────────────────
//
// Defaults match the ITU-T G.114 / RFC 3550 references for voice
// quality. Any of these can be overridden per-tenant via env; the
// renderer + the checks read from the same accessors so the icon
// in the phonestatus follow-up always agrees with the verdict in
// voicediag.

function num(envKey, fallback) {
  const raw = Number(process.env[envKey]);
  return Number.isFinite(raw) ? raw : fallback;
}

// Latency (one-way estimate, milliseconds)
export const getLatencyWarnMs  = () => num('WAN_STANDARD_LATENCY_WARN_MS',  150);
export const getLatencyErrorMs = () => num('WAN_STANDARD_LATENCY_ERROR_MS', 400);

// Jitter (inter-packet arrival variation, milliseconds)
export const getJitterWarnMs   = () => num('WAN_STANDARD_JITTER_WARN_MS',    30);
export const getJitterErrorMs  = () => num('WAN_STANDARD_JITTER_ERROR_MS',   50);

// Packet loss (percent 0-100)
export const getLossWarnPct    = () => num('WAN_STANDARD_LOSS_WARN_PCT',      1);
export const getLossErrorPct   = () => num('WAN_STANDARD_LOSS_ERROR_PCT',     3);

// MOS (Mean Opinion Score, 1.0-5.0 — HIGHER is better, so warn/err
// mean "value FALLS BELOW this")
export const getMosWarn        = () => num('WAN_STANDARD_MOS_WARN',           4.0);
export const getMosError       = () => num('WAN_STANDARD_MOS_ERROR',          3.5);

// Healthscore (Prisma AIOps roll-up, 0-100 — HIGHER is better)
export const getHealthscoreWarn  = () => num('WAN_STANDARD_HEALTHSCORE_WARN',  80);
export const getHealthscoreError = () => num('WAN_STANDARD_HEALTHSCORE_ERROR', 60);

// ─── Utilities used by multiple checks ────────────────────────────

/**
 * Safe number-of-links accessor. WAN checks that grade the whole
 * site (healthscore, alarms) don't care about link count, but the
 * per-link checks below use it to short-circuit when there are no
 * links at all (returns skipped with an actionable message).
 */
export function getLinks(ctx) {
  const raw = ctx?.sdwanData?.links;
  return Array.isArray(raw) ? raw : [];
}

/** Label a link for messages. Kept short so aggregate messages
 *  don't blow past Webex's chat readability. */
export function labelForLink(link) {
  const name = link?.interfaceName || link?.interfaceId || 'link';
  const el = link?.elementName ? `@${link.elementName}` : '';
  const tx = link?.transportType ? ` [${link.transportType}]` : '';
  return `${name}${el}${tx}`;
}

/**
 * Evaluate a numeric per-link metric against warn/error thresholds
 * across every path, returning a CheckResult. Worst path drives
 * severity — a single bad link takes precedence over three good
 * ones because "the phone routed over the bad path sounds terrible"
 * is the ticket we're trying to catch.
 *
 * Consolidated here so the four LQM checks (latency / jitter /
 * loss / mos) don't duplicate 40 lines of comparison logic — they
 * pass config in, get a CheckResult out.
 *
 * @param {object} args
 * @param {Array<object>} args.links     ctx.sdwanData.links
 * @param {string} args.metricKey        row property to read (e.g. 'latencyMs')
 * @param {string} args.label            label for messages (e.g. 'latency')
 * @param {string} args.unit             display unit (e.g. 'ms', '%', '')
 * @param {number} args.warnThresh
 * @param {number} args.errorThresh
 * @param {boolean} args.lowIsBad        true → warn/error when value FALLS BELOW threshold (MOS)
 * @param {string} args.standardLabel    for the "compliant range" phrasing
 */
export function evaluatePerLinkMetric({
  links,
  metricKey,
  label,
  unit,
  warnThresh,
  errorThresh,
  lowIsBad = false,
  standardLabel,
}) {
  if (!Array.isArray(links) || links.length === 0) {
    return {
      status: 'skipped',
      message: `No WAN paths reported for this site.`,
      details: null,
      remediation: null,
    };
  }

  const withValue = links.filter((l) => Number.isFinite(l[metricKey]));
  if (withValue.length === 0) {
    return {
      status: 'skipped',
      message: `${label} not available from Prisma for any path (partial fetch).`,
      details: null,
      remediation: null,
    };
  }

  const grade = (v) => {
    if (lowIsBad) {
      if (v < errorThresh)  return 'error';
      if (v < warnThresh)   return 'warn';
      return 'ok';
    }
    if (v > errorThresh)    return 'error';
    if (v > warnThresh)     return 'warn';
    return 'ok';
  };

  const perLink = withValue.map((l) => ({
    link: labelForLink(l),
    value: l[metricKey],
    interfaceId: l.interfaceId,
    verdict: grade(l[metricKey]),
  }));

  const errors = perLink.filter((r) => r.verdict === 'error');
  const warns  = perLink.filter((r) => r.verdict === 'warn');

  const worstLine = (rows) =>
    rows.map((r) => `${r.link} (${r.value}${unit})`).join(', ');

  const details = {
    total: perLink.length,
    ok: perLink.filter((r) => r.verdict === 'ok').length,
    warn: warns.length,
    error: errors.length,
    perLink,
    warnThresh,
    errorThresh,
    standardLabel,
  };

  if (errors.length > 0) {
    return {
      status: 'error',
      message:
        `${errors.length} path(s) with ${label} past error threshold ` +
        `(${standardLabel}): ${worstLine(errors)}.`,
      details,
      remediation: null,
    };
  }

  if (warns.length > 0) {
    return {
      status: 'warn',
      message:
        `${warns.length} path(s) with elevated ${label} ` +
        `(${standardLabel}): ${worstLine(warns)}.`,
      details,
      remediation: null,
    };
  }

  return {
    status: 'ok',
    message: `All ${perLink.length} path(s) with ${label} in the compliant range (${standardLabel}).`,
    details,
    remediation: null,
  };
}