// src/services/voiceDiag/checks/wan/wanAlarms.js
//
// Recent Prisma alarms surface. Not a threshold check — the
// severity is a direct pass-through of what Prisma raised:
//
//   - critical → error
//   - major    → warn
//   - minor    → info-only (stays 'ok', but details show the count)
//
// The window matches whatever `collectSdwanForStore` used — same
// value the /voicediag "WAN window" banner shows. An "active
// incident" that Prisma sees is materially more urgent than a
// snapshot LQM anomaly, so this deliberately runs even when the
// per-metric checks are all green — a critical alarm 45 min ago
// is still the operator's problem.
//
// The message field DOES NOT dump raw JSON. Prisma populates each
// alarm's `info` field with a nested object (e.g. `{ vpn_reasons:
// [{ code: 'NETWORK_VPNLINK_DOWN', vpnlink_id: '...' }, …] }`) that
// is useful to a person reading the Prisma UI but noise in a chat
// message. Instead we roll samples up by (code + severity), humanize
// the code, and mention the newest occurrence with an "N min ago"
// style relative timestamp.
//
// When alarms fire but every physical Link State check is green,
// the message calls out the mismatch and explains it (usually the
// overlay/VPN mesh is flapping while the physical circuits stay up).
// This addresses the "looks green but 20 alarms" cognitive dissonance
// operators would otherwise have to reason through themselves.

import { maybeSkippedByKillSwitch } from './_helpers.js';
import {
  categorizeAlarm,
  humanizeAlarmCode,
  rollupAlarms,
  countByCategory,
  humanizeAge,
  humanizeWindow,
} from '../../../enrichment/alarmSemantics.js';

export const WAN_ALARMS_STANDARDS = Object.freeze({
  criticalAllowed: 0,
  majorAllowed: 0,
});

export const wanAlarmsCheck = {
  id: 'wanAlarms',
  // Label is intentionally generic (no window suffix) — the effective
  // window is dynamic (comes from ctx.sdwanData.window.alarmMinutes)
  // and gets baked into the message rather than the label, since
  // labels are static across the process lifetime.
  label: 'SD-WAN Alarms',
  requires: ['sdwanSite'],
  scope: null,
  standards: WAN_ALARMS_STANDARDS,

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

    const alarms = ctx.sdwanData?.alarms;
    if (!alarms) {
      return {
        status: 'skipped',
        message: 'Alarms feed not available from Prisma (partial fetch).',
        details: null,
        remediation: null,
      };
    }

    const { critical = 0, major = 0, minor = 0 } = alarms.last1h || {};
    const samples = Array.isArray(alarms.samples) ? alarms.samples : [];
    const alarmWindowMin = ctx.sdwanData?.window?.alarmMinutes || 60;
    const windowLabel = humanizeWindow(alarmWindowMin);

    // Roll up samples so 20 identical NETWORK_ANYNETLINK_DOWN alarms
    // become 1 line with "×20" — same shape the WAN follow-up renderer
    // uses, kept consistent by pulling the helper from a shared module.
    const rollups = rollupAlarms(samples);
    const byCategory = countByCategory(samples);

    // Physical vs overlay heuristic. Only ever a HINT — a store where
    // Link State also reports paths down doesn't need us telling them
    // "physical is up".
    const linksAllUp = allPhysicalLinksUp(ctx?.sdwanData?.links);

    const details = {
      critical, major, minor,
      window: windowLabel,
      byCategory,
      recentSamples: rollups.slice(0, 3).map((r) => ({
        code: r.code,
        humanized: humanizeAlarmCode(r.code),
        category: categorizeAlarm(r.code),
        severity: r.severity,
        count: r.count,
        age: humanizeAge(r.newestTs),
        ts: r.newestTs,
      })),
    };

    if (critical > 0) {
      return {
        status: 'error',
        message: buildMessage({
          count: critical, severityLabel: 'critical',
          windowLabel, rollups, byCategory, linksAllUp,
        }),
        details,
        remediation: null,
      };
    }

    if (major > 0) {
      return {
        status: 'warn',
        message: buildMessage({
          count: major, severityLabel: 'major',
          windowLabel, rollups, byCategory, linksAllUp,
        }),
        details,
        remediation: null,
      };
    }

    if (minor > 0) {
      return {
        status: 'ok',
        message:
          `${minor} minor alarm${minor === 1 ? '' : 's'} in the last ` +
          `${windowLabel}, no critical or major.`,
        details,
        remediation: null,
      };
    }

    return {
      status: 'ok',
      message: `No alarms raised in the last ${windowLabel}.`,
      details,
      remediation: null,
    };
  },
};

/**
 * Build the WARN / ERROR message body. Structure:
 *   <N> <sev> alarm(s) in last <window> — most common: <humanized code>
 *   (×N, latest <N> min ago). <optional physical-vs-overlay hint>.
 */
function buildMessage({
  count, severityLabel, windowLabel, rollups, byCategory, linksAllUp,
}) {
  // Top rollup entry drives the human summary. Preserves severity
  // ordering (critical > major > minor) so the "most notable" alarm
  // is what we cite even if a lower-severity code has a higher count.
  const top = rollups[0];
  const parts = [
    `${count} ${severityLabel} alarm${count === 1 ? '' : 's'} in the last ${windowLabel}`,
  ];

  if (top) {
    const label = humanizeAlarmCode(top.code);
    const suffix = [];
    if (top.count > 1)  suffix.push(`×${top.count}`);
    if (top.newestTs)   suffix.push(`latest ${humanizeAge(top.newestTs)}`);
    const suffixStr = suffix.length > 0 ? ` (${suffix.join(', ')})` : '';
    parts.push(` — most common: ${label}${suffixStr}`);
  }

  // Physical-vs-overlay clarifier — the most common source of
  // "looks green but 20 alarms" confusion. Only emit when we
  // can confidently distinguish the two cases.
  const overlayHeavy = byCategory.overlay > 0
    && byCategory.overlay >= byCategory.physical;
  if (overlayHeavy && linksAllUp === true) {
    parts.push(
      '. These affect SD-WAN overlay/VPN tunnels between sites; ' +
      'physical WAN paths are all up per the Link State check.',
    );
  } else if (byCategory.physical > 0 && linksAllUp === false) {
    parts.push(
      '. Physical WAN interfaces are affected — see the Link State ' +
      'check for the impacted path(s).',
    );
  } else if (byCategory.device > 0) {
    parts.push('. Device / ION appliance affected.');
  } else {
    parts.push('.');
  }

  return parts.join('');
}

/**
 * True iff every physical link on the site reports up. Returns
 * `null` when the link array is missing or empty so the caller can
 * decide whether to emit the physical-vs-overlay hint at all.
 */
function allPhysicalLinksUp(links) {
  if (!Array.isArray(links) || links.length === 0) return null;
  let seen = 0;
  for (const l of links) {
    // Unknown state → treat as "cannot confirm" and short-circuit
    // rather than lie about the state.
    if (l?.up === null || l?.up === undefined) continue;
    seen += 1;
    if (l.up === false) return false;
  }
  return seen > 0 ? true : null;
}