Whale position tracker

// Whale position tracker: every time a large tracked Hyperliquid wallet opens, adds to, cuts, flips or closes a position,
// or gets liquidated. Node 18+, no dependencies. Polls GET /whales/feed with ?since= and prints one line per change.
//
//   export BLOCKMETRIC_API_KEY=bm_live_...            # optional: without a key it uses keyless public access
//   export BLOCKMETRIC_BASE_URL=https://<domain>/api/v1
//   node whale-tracker.mjs
//
// Options: MIN_USD (1000000 = changes of at least $1M), COIN (all), WATCH (only these addresses, comma-separated),
// POLL_SECONDS (60), SINCE_MINUTES (60 = start with the last hour), ONCE=1 (one poll, then exit).

const BASE = (process.env.BLOCKMETRIC_BASE_URL ?? '').replace(/\/+$/, '')
const KEY = process.env.BLOCKMETRIC_API_KEY
if (!BASE) throw new Error('Set BLOCKMETRIC_BASE_URL, e.g. https://<domain>/api/v1')
const MIN_USD = Number(process.env.MIN_USD ?? 1_000_000)
const COIN = process.env.COIN || undefined
const WATCH = new Set((process.env.WATCH ?? '').split(',').map((a) => a.trim().toLowerCase()).filter(Boolean))
const POLL_SECONDS = Number(process.env.POLL_SECONDS ?? 60)
const SINCE_MINUTES = Number(process.env.SINCE_MINUTES ?? 60)
const ONCE = process.env.ONCE === '1'
const sleep = (ms) => new Promise((r) => setTimeout(r, ms))

async function api(path, params = {}) {
  const url = new URL(BASE + path)
  for (const [k, v] of Object.entries(params)) if (v !== undefined && v !== null && v !== '') url.searchParams.set(k, String(v))
  for (let attempt = 1; ; attempt++) {
    const res = await fetch(url, { headers: KEY ? { Authorization: `Bearer ${KEY}` } : { 'X-Blockmetric-Access': 'public' }, signal: AbortSignal.timeout(30_000) })
    if (res.status === 429 && attempt < 5) {
      await sleep(Number(res.headers.get('Retry-After') ?? 5) * 1000)
      continue
    }
    const body = await res.json()
    if (!res.ok) throw new Error(`${res.status} ${body.error?.code}: ${body.error?.message}`)
    return body
  }
}

const usd = (n) => `$${Math.abs(n) >= 1e6 ? `${(Math.abs(n) / 1e6).toFixed(2)}M` : `${(Math.abs(n) / 1e3).toFixed(0)}K`}`
const px = (p) => p.toLocaleString('en-US', { maximumFractionDigits: p >= 1000 ? 0 : p >= 1 ? 2 : 6 })
const short = (a) => `${a.slice(0, 6)}…${a.slice(-4)}`
const VERB = { open: 'opened', increase: 'added to', decrease: 'cut', close: 'closed', flip: 'flipped to', liquidated: 'was liquidated on' }

/** One line per position change; the leverage and liquidation price come from the position poll. */
export function line(e) {
  const who = e.label ?? short(e.address)
  const d = e.data ?? {}
  const after = d.positionUsd ? ` (now ${usd(d.positionUsd)}${d.leverage ? `, ${d.leverage}x` : ''}${d.liqPx ? `, liq. ${px(d.liqPx)}` : ''})` : ''
  return `${e.ts.slice(11, 16)} UTC  ${who} ${VERB[e.kind] ?? e.kind} ${e.coin} ${e.side}: ${usd(e.usdDelta)} at ${px(e.price)}${after}`
}

async function main() {
  let since = new Date(Date.now() - SINCE_MINUTES * 60_000).toISOString()
  const seen = new Set()
  console.log(`Whale position changes of at least ${usd(MIN_USD)}${COIN ? ` in ${COIN}` : ''}${WATCH.size ? ` by ${WATCH.size} watched wallets` : ''}.`)
  for (;;) {
    // Newest first: collect every page back to `since`, then print oldest first.
    const batch = []
    let cursor
    do {
      const { data, meta } = await api('/whales/feed', { since, minUsd: MIN_USD, coin: COIN, limit: 200, cursor })
      batch.push(...data)
      cursor = meta.nextCursor ?? undefined
    } while (cursor)
    for (const e of batch.reverse()) {
      if (seen.has(e.id) || (WATCH.size && !WATCH.has(e.address.toLowerCase()))) continue
      seen.add(e.id)
      console.log(line(e))
      if (e.ts > since) since = e.ts
    }
    if (ONCE) break
    await sleep(POLL_SECONDS * 1000)
  }
}

main().catch((e) => {
  console.error(e.message)
  process.exit(1)
})