// 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 /wanstatus renderer 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);

// ─── Per-application (DPI) audio-quality thresholds ──────────────
// Applied against the WORST-window value in the series (not the avg)
// since these signals come as 288-point 24h time series and the whole
// point of app-quality checks is to catch transient degradation the
// LQM link-probe average smooths away. Defaults match the ITU-T
// references but are DELIBERATELY less strict than the link-probe
// thresholds because false positives from a single bad 5-min window
// would drown the operator in noise. Tune via env if your traffic
// mix is more sensitive.
//
// MOS (worst-window, lower is worse — call quality drops)
export const getAppMosWarn      = () => num('WAN_STANDARD_APP_MOS_WARN',        4.0);
export const getAppMosError     = () => num('WAN_STANDARD_APP_MOS_ERROR',       3.5);

// Loss (worst-window percentage, higher is worse)
export const getAppLossWarnPct  = () => num('WAN_STANDARD_APP_LOSS_WARN_PCT',   5);
export const getAppLossErrorPct = () => num('WAN_STANDARD_APP_LOSS_ERROR_PCT', 15);

// Jitter (worst-window ms, higher is worse)
export const getAppJitterWarnMs  = () => num('WAN_STANDARD_APP_JITTER_WARN_MS',  30);
export const getAppJitterErrorMs = () => num('WAN_STANDARD_APP_JITTER_ERROR_MS', 50);

// ─── 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}`;
}

/**
 * Accessor for the per-app audio-quality summary computed in
 * sdwanEnrichment.js. Returns a small envelope so the caller can
 * distinguish four states cleanly:
 *
 *   {configured:false, summary:null, fetchError:null}
 *       Voice-app env not set → checks return "not configured"
 *       skipped. See sdwanEnrichment.js:resolveVoiceAppConfig() for
 *       the env-var contract (PRISMA_APP_ID_VOICE, or
 *       PRISMA_APP_ID_RTP_BASE for backwards compat). This is a
 *       config decision, not a transient failure.
 *
 *   {configured:true,  summary:null, fetchError:'<msg>'}
 *       Env set + Prisma fetch failed (429 storm, timeout, schema
 *       drift). Different UX from "not configured" — surfaces the
 *       real error so the operator can retry or fix.
 *
 *   {configured:true,  summary:{...},fetchError:null}
 *       Fetch succeeded but Prisma returned zero valid samples
 *       (no matching RTP traffic in the window). Skipped with a
 *       "no traffic seen" message.
 *
 *   {configured:true,  summary:{...validSamples>0...}, fetchError:null}
 *       Green path — check grades against the summary.
 *
 * @param {object} ctx
 * @param {'mos'|'loss'|'jitter'|'bandwidth'} which
 */
export function getAppAudio(ctx, which) {
  const container = ctx?.sdwanData?.appAudio || null;
  if (!container) {
    return {
      configured: false,
      summary: null,
      fetchError: null,
      appName: null,
      detailsUrl: null,
    };
  }
  // Error-scope names are app-agnostic ("app.voice.<metric>") so the
  // check doesn't have to know which specific voice app is
  // configured — it just asks "was the fetch for MOS on the voice
  // app OK?" See sdwanEnrichment.js:recordFailure() for the writer.
  const scope = `app.voice.${which}`;
  const errRec = Array.isArray(ctx?.sdwanData?.errors)
    ? ctx.sdwanData.errors.find((e) => e?.scope === scope)
    : null;
  return {
    configured: true,
    summary:    container[which] || null,
    fetchError: errRec?.message || null,
    appName:    container.appName || 'voice',
    // SCM UI deep-link computed once in sdwanEnrichment.js. Threaded
    // through here so the check details carry it into the voiceDiag
    // renderer as a "View in Prisma UI" link.
    detailsUrl: container.detailsUrl || null,
  };
}

/**
 * Humanize the raw Prisma unit string into a display-friendly suffix.
 * The API returns strings like `"percentage"` and `"milliseconds"`
 * which read like error messages when concatenated into a UI value
 * (`"11.83percentage"`). This normalizes to the units an operator
 * actually recognizes.
 *
 * Exposed so both the renderer and the check message use the same
 * mapping — divergence there would produce mismatched icons vs
 * numbers.
 */
export function humanizeMetricUnit(raw) {
  if (!raw) return '';
  const lc = String(raw).toLowerCase();
  if (lc === 'percentage' || lc === 'percent')      return '%';
  if (lc === 'milliseconds' || lc === 'ms')         return 'ms';
  if (lc === 'count' || lc === 'gauge' || lc === 'score') return '';
  if (lc === 'kbps')  return 'kbps';
  if (lc === 'mbps')  return 'Mbps';
  if (lc === 'bps')   return 'bps';
  if (lc === 'seconds' || lc === 's') return 's';
  // Anything else — return as-is, prefixed with a space so it's
  // visually separated from the number (`"12 something"` reads
  // better than `"12something"`).
  return ` ${raw}`;
}

/**
 * Grade a per-app audio quality summary against warn/error thresholds.
 * Handles the four cases the envelope from `getAppAudio()` can be in:
 * not-configured, fetch-failed, no-traffic, gradeable.
 *
 * @param {object} args
 * @param {object} args.audio         envelope from getAppAudio():
 *                                    {configured, summary, fetchError, appName}
 * @param {string} args.label         display label ("audio MOS", "audio loss", …)
 * @param {string} args.unit          display unit ("%", "ms", "")
 * @param {number} args.warnThresh
 * @param {number} args.errorThresh
 * @param {boolean} args.lowIsBad     true → warn/error when the
 *                                    WORST-window VALUE FALLS BELOW
 *                                    the threshold (MOS). false →
 *                                    warn/error when the WORST-window
 *                                    value RISES ABOVE (loss, jitter).
 * @param {string} [args.standardLabel]  optional inline "warn > X"
 *                                    description embedded in the message
 * @returns {object} CheckResult
 */
export function evaluateAppAudioMetric({
  audio, label, unit, warnThresh, errorThresh, lowIsBad = false,
  standardLabel,
}) {
  const appName = audio?.appName || 'the voice app';

  if (!audio || audio.configured === false) {
    return {
      status: 'skipped',
      message:
        `Per-app ${label} unavailable — set PRISMA_APP_ID_VOICE in the ` +
        `environment (with optional PRISMA_APP_NAME_VOICE for the display ` +
        `name) to enable per-application DPI metrics.`,
      details: null,
      remediation: null,
    };
  }

  if (audio.fetchError) {
    return {
      status: 'skipped',
      message:
        `Per-app ${label} for ${appName}: Prisma fetch failed — ${audio.fetchError}. ` +
        `Common cause: parallel-request rate limiting (429). Retry in ~30 seconds.`,
      details: { fetchError: audio.fetchError, appName },
      remediation: null,
    };
  }

  const summary = audio.summary;
  if (!summary) {
    return {
      status: 'skipped',
      message:
        `Per-app ${label} for ${appName}: no summary produced (Prisma returned an ` +
        `empty or malformed response). Check paloalto:metrics logs for the raw payload.`,
      details: null,
      remediation: null,
    };
  }
  if (!summary.validSamples || summary.validSamples === 0) {
    return {
      status: 'skipped',
      message:
        `Per-app ${label} for ${appName}: Prisma returned ` +
        `${summary.samples || 0} datapoint(s), all null — no voice traffic ` +
        `matched by DPI in the window.`,
      details: summary,
      remediation: null,
    };
  }

  const worst = lowIsBad ? summary.min : summary.max;
  const grade = (v) => {
    if (v == null) return 'skipped';
    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 status = grade(worst);

  // Percent of samples that were in warn or error range — the "how
  // often was it bad" number that turns the worst-window verdict into
  // an actionable "N% of your voice calls saw this" statistic.
  const bad = summary.values.filter(
    (v) => grade(v) === 'warn' || grade(v) === 'error',
  ).length;
  const badPct = summary.validSamples > 0
    ? Math.round((bad / summary.validSamples) * 100)
    : 0;

  // Store both the raw API unit (for debugging) and the humanized
  // display unit (what the renderer + message use). Overriding the
  // spread unit with the check-arg unit lets each check pick a nice
  // suffix ('%', 'ms') without depending on the API's verbose one.
  const details = {
    ...summary,
    rawUnit: summary.unit || null,
    unit,
    warnThresh,
    errorThresh,
    standardLabel: standardLabel || null,
    worst,
    badSampleCount: bad,
    badSamplePct: badPct,
    appName,
    // SCM UI deep-link. The renderer surfaces this as a
    // "View in Prisma UI" markdown link so an operator can jump from
    // the diag output straight to the Prisma UI dashboard for the
    // exact site+app combination without hunting for it.
    detailsUrl: audio.detailsUrl || null,
  };

  const worstStr = worst == null ? '—' : `${worst}${unit}`;
  const avgStr = summary.avg == null ? '—' : `${summary.avg}${unit}`;
  const cmp = lowIsBad ? '<' : '>';
  const threshStr = status === 'error'
    ? `${cmp} ${errorThresh}${unit}`
    : `${cmp} ${warnThresh}${unit}`;

  if (status === 'error' || status === 'warn') {
    return {
      status,
      message:
        `Actual voice traffic (${appName}) worst-window ${label}: ${worstStr} ${threshStr} ` +
        `(avg ${avgStr} over ${summary.validSamples} × ${summary.interval || '5min'} samples). ` +
        `${badPct}% of samples were ${status === 'error' ? 'in the error range' : 'past warn'}. ` +
        `This is measured on real RTP traffic — the WAN link probes may still look fine.`,
      details,
      remediation: null,
    };
  }

  return {
    status: 'ok',
    message:
      `Actual voice traffic (${appName}) ${label} within range: worst ${worstStr}, ` +
      `avg ${avgStr} across ${summary.validSamples} × ${summary.interval || '5min'} samples.`,
    details,
    remediation: null,
  };
}

/**
 * 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,
  };
}