// src/services/renderers/wanDiagnosticsRenderer.js
//
// Pure markdown renderer for the /phonestatus WAN follow-up message.
// Takes a `collectSdwanForStore(storeNum)` result and produces the
// section that shows healthscore + per-path LQM + active alarms.
//
// Design mirrors renderDectDiagnosticsMarkdown in
// services/renderers/phoneStatusRenderer.js:
//   - Pure function, no I/O.
//   - Returns '' when there's genuinely nothing to say (caller
//     no-ops on empty string).
//   - Bullet lists only — Webex markdown doesn't render tables
//     reliably, and the port-hygiene checks already prove bullets
//     scan fine for per-device drilldowns.
//   - Threshold-based icons (✅ good, ⚠️ warn, ❌ error, ❓ unknown)
//     so a scanning operator can locate the bad link visually
//     without reading numbers.

import {
  categorizeAlarm,
  humanizeAlarmCode,
  rollupAlarms as sharedRollupAlarms,
  humanizeAge,
  isVoiceRelevantAlarm,
  coerceAlarmTsMs,
} from '../enrichment/alarmSemantics.js';
import { formatDisplayTime } from '../../utils/time.js';

// Thresholds are read from env at render time so the rendered
// icons stay in sync with the check bucket verdicts. Same defaults
// as services/voiceDiag/checks/wan/_helpers.js — kept in sync by
// convention (there's a regression test that pins them together).
function readThresholds() {
  const num = (k, fallback) => {
    const raw = Number(process.env[k]);
    return Number.isFinite(raw) ? raw : fallback;
  };
  return {
    latencyWarn:  num('WAN_STANDARD_LATENCY_WARN_MS',   150),
    latencyError: num('WAN_STANDARD_LATENCY_ERROR_MS',  400),
    jitterWarn:   num('WAN_STANDARD_JITTER_WARN_MS',     30),
    jitterError:  num('WAN_STANDARD_JITTER_ERROR_MS',    50),
    lossWarn:     num('WAN_STANDARD_LOSS_WARN_PCT',       1),
    lossError:    num('WAN_STANDARD_LOSS_ERROR_PCT',      3),
    mosWarn:      num('WAN_STANDARD_MOS_WARN',            4.0),
    mosError:     num('WAN_STANDARD_MOS_ERROR',           3.5),
    hsWarn:       num('WAN_STANDARD_HEALTHSCORE_WARN',   80),
    hsError:      num('WAN_STANDARD_HEALTHSCORE_ERROR',  60),
  };
}

/**
 * Render a Prisma SD-WAN follow-up message.
 *
 * @param {object} data  Result from collectSdwanForStore(storeNum).
 * @param {object} [opts]
 * @param {string} [opts.storeNum]    used in the section header
 * @param {boolean} [opts.footer=true] emit the "pulled at HH:MM:SS" footer
 * @returns {string} markdown (or '' when there's nothing to render)
 */
export function renderWanDiagnosticsMarkdown(data, opts = {}) {
  const { storeNum, footer = true } = opts;
  if (!data || typeof data !== 'object') return '';

  // No-site case: this is the "not a Prisma-managed store" happy
  // path. We deliberately DON'T show a header for it — the follow-up
  // caller only kicks the runner when discovery said yes, so seeing
  // this branch here means something raced. Return ''.
  if (!data.site) return '';

  const t = readThresholds();

  let out = `**WAN Diagnostics (Prisma SD-WAN) — Store ${storeNum || data.storeNum || '?'}**\n\n`;

  // Site + healthscore header line.
  const hs = data.healthscore;
  const hsIcon = hs?.value == null ? '❓' : iconFromNumeric(hs.value, t.hsError, t.hsWarn, /* lowIsBad */ true);
  const hsText = hs?.value == null ? 'n/a' : `${hs.value}/100`;
  const elCount = Array.isArray(data.elements) ? data.elements.length : 0;
  const linkCount = Array.isArray(data.links) ? data.links.length : 0;
  const windowLabel = data.window?.minutes ? ` • Window: ${humanWindowLabel(data.window.minutes)}` : '';
  out +=
    `Site: **${data.site.name}** (${elCount} element${elCount === 1 ? '' : 's'}, ` +
    `${linkCount} WAN path${linkCount === 1 ? '' : 's'}) • Healthscore: ${hsIcon} ${hsText}` +
    `${windowLabel}\n\n`;

  // Per-path bullet list. Ordered by "worst path first" so a
  // scanning operator sees the offender at the top.
  if (linkCount > 0) {
    const ranked = [...data.links].sort((a, b) => rankLink(b, t) - rankLink(a, t));
    for (const link of ranked) {
      out += renderOneLink(link, t);
    }
  } else {
    out += `_No WAN path metrics available for this site._\n`;
  }

  // Overlay / VPN tunnels — overall status; list downs only.
  out += renderTunnelsSection(data.tunnels, data.links);

  // Per-app "Application Path Details" section — real voice-quality
  // signal from DPI on actual RTP traffic. Which app is measured
  // depends on the tenant's configured voice app (Webex_Calling_RTP,
  // rtp-base, MS_Teams_RTP, etc.). Shown BEFORE alarms because when
  // it fires, it's usually more actionable than an overlay alarm:
  // it's "your calls sounded bad at these times", not "a tunnel
  // bounced but recovered". Feature-gated on PRISMA_APP_ID_VOICE
  // (backwards-compat: PRISMA_APP_ID_RTP_BASE) — omitted entirely
  // when not configured so this doesn't add empty sections for
  // tenants that opted out.
  if (data.appAudio) {
    out += renderAppAudioSection(data.appAudio, data.window);
  }

  // Alarms: severity totals + code rollup + last 5 with timestamps.
  // When voice DPI looks bad and recent alarms are overlay/physical/
  // device, call out the correlation (not proof of causality).
  const totalAlarms =
    (data.alarms?.last1h?.critical || 0) +
    (data.alarms?.last1h?.major || 0) +
    (data.alarms?.last1h?.minor || 0);
  if (totalAlarms > 0) {
    const { critical = 0, major = 0, minor = 0 } = data.alarms.last1h;
    const parts = [];
    if (critical > 0) parts.push(`${critical} critical`);
    if (major > 0)    parts.push(`${major} major`);
    if (minor > 0)    parts.push(`${minor} minor`);
    const alarmWindowLabel = data.window?.alarmMinutes
      ? humanWindowLabel(data.window.alarmMinutes)
      : '1h';
    out += `\n🚨 Alarms (last ${alarmWindowLabel}): ${parts.join(', ')}\n`;

    const samples = data.alarms.samples || [];
    const rollups = sharedRollupAlarms(samples);
    for (const r of rollups.slice(0, 5)) {
      const label = humanizeAlarmCode(r.code);
      const category = categorizeAlarm(r.code);
      const age = r.newestTs ? humanizeAge(r.newestTs) : '';
      const count = r.count > 1 ? ` ×${r.count}` : '';
      out +=
        `   - ${sevIcon(r.severity)} **${label}**${count} \`${r.code}\`` +
        ` _(${category}${age ? `, ${age}` : ''})_\n`;
    }
    if (rollups.length > 5) {
      out += `   - _+${rollups.length - 5} more alarm code${rollups.length - 5 === 1 ? '' : 's'}._\n`;
    }

    const recent = samples.slice(0, 5);
    if (recent.length > 0) {
      out += `   _Most recent:_\n`;
      for (const s of recent) {
        const label = humanizeAlarmCode(s.code);
        const when = formatAlarmWhen(s.ts);
        const voiceBit = isVoiceRelevantAlarm(s.code) ? ' · may affect voice' : '';
        out +=
          `   - ${sevIcon(s.severity)} **${label}**` +
          `${when ? ` — ${when}` : ''}${voiceBit}\n`;
      }
    }

    const voiceCorr = voiceAlarmCorrelationNote(data.appAudio, samples);
    if (voiceCorr) out += `   _${voiceCorr}_\n`;
  }

  // Per-metric fetch failures shown as small warnings so the operator
  // knows the display is incomplete rather than "all clear".
  if (Array.isArray(data.errors) && data.errors.length > 0) {
    out += `\n_Partial fetch:_\n`;
    for (const e of data.errors) {
      out += `   - \`${e.scope}\` failed: ${e.message}\n`;
    }
  }

  if (footer) {
    const store = storeNum || data.storeNum;
    out += `\n*WAN metrics pulled at ${formatDisplayTime()} from Prisma SD-WAN. ` +
      `Use \`/voicediag ${store} --only wanLatency,wanJitter,wanLoss,wanMos,wanHealthscore,wanLinkState,wanAlarms\` for link-probe breakdowns, ` +
      `or \`/voicediag ${store} --only wanAppRtpMos,wanAppRtpLoss,wanAppRtpJitter\` for per-app RTP quality.*`;
  }

  return out.trim();
}

// ─── internals ─────────────────────────────────────────────────────

/**
 * Human-friendly window label: 15m / 1h / 6h / 24h.
 * Mirrored from voiceDiagRenderer.js — kept in-file to avoid a
 * tiny shared-utils import for a 5-line helper.
 */
function humanWindowLabel(minutes) {
  if (!Number.isFinite(minutes) || minutes <= 0) return `${minutes}m`;
  if (minutes >= 1440 && minutes % 1440 === 0) return `${minutes / 1440}d`;
  if (minutes >= 60 && minutes % 60 === 0) return `${minutes / 60}h`;
  return `${minutes}m`;
}

/**
 * Render the "Voice Traffic Quality" section — real DPI measurements
 * on actual RTP frames rather than synthetic link probes. Shows
 * worst-window / avg / % of samples degraded per metric, with icons
 * keyed off the WORST-window value (that's the signal that actually
 * correlates with "the operator got a bad-calls ticket").
 *
 * Section header includes the configured voice-app name (e.g.
 * "Webex_Calling_RTP", "rtp-base") so the operator knows which DPI
 * signature was measured — different apps have very different
 * traffic patterns and one may show issues the other misses.
 *
 * @param {object} appAudio  ctx.sdwanData.appAudio
 * @param {object} window    ctx.sdwanData.window
 */
function renderAppAudioSection(appAudio, window) {
  if (!appAudio) return '';
  const { mos, loss, jitter, bandwidth, appName, detailsUrl } = appAudio;
  // If literally every metric is null/empty, skip entirely — usually
  // means the tenant has the env var set but this site has no RTP
  // traffic yet.
  const anyData = [mos, loss, jitter, bandwidth].some(
    (s) => s && s.validSamples > 0,
  );
  if (!anyData) return '';

  const winLabel = window?.minutes ? humanWindowLabel(window.minutes) : '7d';
  // Deep-link into the Strata Cloud Manager "Application Path
  // Details" page for this site+app. Only rendered when a URL was
  // computed (detailsUrl is null if either id is missing).
  const linkSuffix = detailsUrl
    ? ` — [View in Prisma UI](${detailsUrl})`
    : '';

  let out = `\n**Voice Traffic Quality (${appName || 'voice'}, last ${winLabel})**${linkSuffix}\n`;
  out += `_Measured on real RTP frames via Prisma DPI — worst-window matters more than avg for voice._\n`;

  const mosLine    = fmtAppMetricLine('MOS',        mos,       '',   3.5,  4.0, /* lowIsBad */ true);
  const lossLine   = fmtAppMetricLine('Loss',       loss,      '%',  15,   5,   /* lowIsBad */ false);
  const jitterLine = fmtAppMetricLine('Jitter',     jitter,    'ms', 50,   30,  /* lowIsBad */ false);
  const bwLine     = fmtAppMetricLine('Bandwidth',  bandwidth, 'Mbps', null, null, /* lowIsBad */ false);

  for (const line of [mosLine, lossLine, jitterLine, bwLine].filter(Boolean)) {
    out += `- ${line}\n`;
  }

  // Phase 1: per-path_type breakout (VPN vs DirectInternet vs …).
  const byPt = appAudio.byPathType || {};
  const ptKeys = Object.keys(byPt);
  if (ptKeys.length > 0) {
    out += `_By path type:_\n`;
    for (const pt of ptKeys) {
      const row = byPt[pt];
      const bits = [];
      if (row.loss?.validSamples > 0) {
        bits.push(`loss worst ${row.loss.max}%`);
      }
      if (row.jitter?.validSamples > 0) {
        bits.push(`jitter worst ${row.jitter.max}ms`);
      }
      if (row.bandwidth?.validSamples > 0) {
        bits.push(`bw avg ${row.bandwidth.avg}Mbps`);
      }
      if (bits.length) out += `- **${pt}:** ${bits.join(' · ')}\n`;
    }
  }

  // Phase 2: per-circuit attribution when enabled.
  const byPath = appAudio.byPath || {};
  const pathKeys = Object.keys(byPath);
  if (pathKeys.length > 0) {
    out += `_By WAN circuit (path attribution):_\n`;
    for (const pathId of pathKeys) {
      const row = byPath[pathId];
      const bits = [];
      if (row.loss?.validSamples > 0) bits.push(`loss worst ${row.loss.max}%`);
      if (row.jitter?.validSamples > 0) bits.push(`jitter worst ${row.jitter.max}ms`);
      if (bits.length) out += `- \`${pathId}\`: ${bits.join(' · ')}\n`;
    }
  }

  return out;
}

function renderTunnelsSection(tunnels, links) {
  const list = Array.isArray(tunnels) ? tunnels : [];
  if (list.length === 0) return '';

  const physicalUp = Array.isArray(links)
    && links.length > 0
    && links.every((l) => l.up !== false);

  const down = list.filter((t) => t.up === false);
  const up = list.filter((t) => t.up === true);
  const unknown = list.filter((t) => t.up == null);
  const total = list.length;

  let summary;
  if (down.length === 0 && unknown.length === 0) {
    summary = `✅ all ${total} up`;
  } else if (down.length === 0 && up.length === 0) {
    summary = `❓ ${total} inventoried (status unknown)`;
  } else if (down.length === 0) {
    summary = `✅ ${up.length}/${total} up` +
      (unknown.length ? ` · ${unknown.length} unknown` : '');
  } else {
    summary = `❌ ${down.length} down / ${total}` +
      (up.length ? ` · ${up.length} up` : '') +
      (unknown.length ? ` · ${unknown.length} unknown` : '');
  }

  let out = `\n**Overlay tunnels** — ${summary}\n`;

  // All-unknown: one inventory note, no peer spam.
  if (down.length === 0 && up.length === 0 && unknown.length > 0) {
    out += `- ❓ Tunnel inventory returned ${total} link(s) but peer/status fields were empty — check Prisma UI topology for this site.\n`;
    return out;
  }

  // Only list downs. Healthy tunnels stay in the summary line.
  const toShow = [...down].sort((a, b) => {
    if (a.recentAlarm !== b.recentAlarm) return a.recentAlarm ? -1 : 1;
    return String(a.peerLabel || '').localeCompare(String(b.peerLabel || ''));
  }).slice(0, 8);

  for (const t of toShow) {
    const peer = (t.peerLabel && t.peerLabel !== 'peer')
      ? t.peerLabel
      : (t.peerSiteId || 'peer');
    const circuitBit = t.circuitName ? ` · ${t.circuitName}` : '';
    const ifBit = t.relatedInterfaceId ? ` · if ${t.relatedInterfaceId}` : '';
    const alarmBit = t.recentAlarm ? ' · ⚠️ recent alarm' : '';
    out += `- ❌ **${peer}** — DOWN${circuitBit}${ifBit}${alarmBit}\n`;
  }
  if (down.length > toShow.length) {
    out += `- _+${down.length - toShow.length} more down tunnel(s)._\n`;
  }
  if (down.length > 0 && physicalUp) {
    out += `_Note: overlay down while physical WAN paths look up — voice may still be impacted._\n`;
  }
  return out;
}

/**
 * Format an alarm timestamp for chat: wall clock + relative age.
 */
function formatAlarmWhen(ts) {
  const ms = coerceAlarmTsMs(ts);
  if (ms == null) return humanizeAge(ts) || '';
  const wall = formatDisplayTime(new Date(ms));
  const age = humanizeAge(new Date(ms).toISOString());
  return age ? `${wall} (${age})` : wall;
}

/**
 * Heuristic: when voice DPI is degraded and recent alarms are
 * overlay/physical/device, note possible correlation (not causation).
 */
function voiceAlarmCorrelationNote(appAudio, samples) {
  if (!appAudio || !Array.isArray(samples) || samples.length === 0) return '';
  if (!voiceQualityLooksDegraded(appAudio)) return '';
  const relevant = samples.filter((s) => isVoiceRelevantAlarm(s.code));
  if (relevant.length === 0) return '';
  const cats = new Set(relevant.map((s) => categorizeAlarm(s.code)));
  const catList = [...cats].join('/');
  return (
    `Voice DPI looks degraded in this window and ${relevant.length} ` +
    `${catList} alarm(s) may help explain it (correlation, not proof).`
  );
}

function voiceQualityLooksDegraded(appAudio) {
  const mosBad = appAudio.mos?.validSamples > 0 && appAudio.mos.min != null && appAudio.mos.min < 3.5;
  const lossBad = appAudio.loss?.validSamples > 0 && appAudio.loss.max != null && appAudio.loss.max > 5;
  const jitterBad = appAudio.jitter?.validSamples > 0 && appAudio.jitter.max != null && appAudio.jitter.max > 50;
  return mosBad || lossBad || jitterBad;
}

/**
 * One row of the voice-traffic-quality section.
 *
 * @param {string} label
 * @param {object|null} summary   {avg, min, max, samples, validSamples, ...}
 * @param {string} unit           display unit ("%", "ms", "", "Mbps")
 * @param {number|null} errThresh
 * @param {number|null} warnThresh
 * @param {boolean} lowIsBad      true for MOS (lower is worse)
 */
function fmtAppMetricLine(label, summary, unit, errThresh, warnThresh, lowIsBad) {
  if (!summary) return '';
  if (summary.validSamples === 0) {
    return `❓ **${label}** — no data (${summary.samples || 0} samples, all null)`;
  }
  const worst = lowIsBad ? summary.min : summary.max;
  let icon;
  if (errThresh == null && warnThresh == null) {
    icon = 'ℹ️';  // no threshold → context-only (bandwidth)
  } else {
    icon = iconFromNumeric(worst, errThresh, warnThresh, lowIsBad);
  }
  const worstLabel = lowIsBad ? 'worst (lowest)' : 'worst';
  return (
    `${icon} **${label}** — ${worstLabel}: **${worst}${unit}** • ` +
    `avg: ${summary.avg}${unit} • ${summary.validSamples}/${summary.samples} samples ` +
    `@ ${summary.interval || '5min'}`
  );
}

function renderOneLink(link, t) {
  const nameLabel = link.interfaceName || link.interfaceId;
  const transport = link.transportType ? ` [${link.transportType}]` : '';
  const net = link.networkName ? ` · ${link.networkName}` : '';
  const upIcon = link.up === null ? '❓' : (link.up ? '✅' : '❌');
  let upText = link.up === null ? 'unknown' : (link.up ? 'up' : 'DOWN');
  if (link.operationalUp != null || link.adminUp != null) {
    const op = link.operationalUp == null ? '?' : (link.operationalUp ? 'op-up' : 'op-down');
    const ad = link.adminUp == null ? '?' : (link.adminUp ? 'admin-up' : 'admin-down');
    upText = `${upText} (${op}/${ad})`;
  }

  let out = `- ${upIcon} **${nameLabel}**${transport}${net} — ${upText}`;

  const parts = [];
  parts.push(fmtMetric('latency', link.latencyMs, 'ms', t.latencyError, t.latencyWarn));
  parts.push(fmtMetric('jitter',  link.jitterMs,  'ms', t.jitterError,  t.jitterWarn));
  parts.push(fmtMetric('loss',    link.lossPct,   '%',  t.lossError,    t.lossWarn));
  parts.push(fmtMetric('MOS',     link.mos,       '',   t.mosError,     t.mosWarn, /* highIsGood */ true));

  const filled = parts.filter(Boolean);
  if (filled.length > 0) {
    out += `\n   ${filled.join(' • ')}`;
  }

  out += '\n';
  return out;
}

function fmtMetric(label, value, unit, errThresh, warnThresh, highIsGood = false) {
  if (value === null || value === undefined) return '';
  const icon = iconFromNumeric(value, errThresh, warnThresh, /* lowIsBad */ highIsGood);
  return `${icon} ${label} ${value}${unit}`;
}

/**
 * Icon selector.
 *
 * For most WAN metrics (latency/jitter/loss), HIGHER is worse. For
 * MOS + healthscore, LOWER is worse. `lowIsBad` flips the sense.
 *
 * @param {number} value
 * @param {number} errThresh  numeric threshold for error severity
 * @param {number} warnThresh numeric threshold for warn severity
 * @param {boolean} lowIsBad  true → low values trigger warn/error
 */
function iconFromNumeric(value, errThresh, warnThresh, lowIsBad = false) {
  if (lowIsBad) {
    if (value < errThresh)  return '❌';
    if (value < warnThresh) return '⚠️';
    return '✅';
  }
  if (value > errThresh)  return '❌';
  if (value > warnThresh) return '⚠️';
  return '✅';
}

function sevIcon(sev) {
  if (sev === 'critical') return '🔴';
  if (sev === 'major')    return '🟠';
  if (sev === 'minor')    return '🟡';
  return '⚪';
}

// rollupAlarms is now shared: services/enrichment/alarmSemantics.js
// (imported as sharedRollupAlarms at the top of this file so both
// this renderer and the wanAlarms check ship the same rollup shape
// + severity ordering).

/**
 * Rank a link on a 0-100 badness scale so the worst path floats to
 * the top of the display. Adds contributions from each metric
 * according to how far past the warn/error thresholds it is.
 */
function rankLink(link, t) {
  let score = 0;
  if (link.up === false) score += 100;
  if (link.latencyMs != null && link.latencyMs > t.latencyWarn)  score += link.latencyMs > t.latencyError ? 30 : 10;
  if (link.jitterMs  != null && link.jitterMs  > t.jitterWarn)   score += link.jitterMs  > t.jitterError  ? 20 : 5;
  if (link.lossPct   != null && link.lossPct   > t.lossWarn)     score += link.lossPct   > t.lossError    ? 25 : 8;
  if (link.mos       != null && link.mos       < t.mosWarn)      score += link.mos       < t.mosError     ? 25 : 8;
  return score;
}