予測市場データの正規化: Polymarket & Kalshi

node prediction-market-normalization.mjs

{
  "prices": ["615000", "615000"],
  "comparison": {
    "equivalent": false,
    "reasons": ["Different resolutionSource"]
  }
}

// Offline teaching example. These are synthetic adapter records, NOT venue API responses.
// Run with Node.js: node prediction-market-normalization.mjs
import { pathToFileURL } from 'node:url'

function nonempty(value, name) {
  if (typeof value !== 'string' || !value.trim()) throw new TypeError(`${name} must be a nonempty string`)
  return value
}

function timestamp(value, name, nullable = false) {
  if (nullable && value === null) return null
  nonempty(value, name)
  const parsed = new Date(value)
  if (!Number.isFinite(parsed.valueOf()) || parsed.toISOString() !== value) {
    throw new TypeError(`${name} must be canonical UTC ISO, including milliseconds`)
  }
  return value
}

// Price per $1-face-value contract, scaled to millionths; no binary float arithmetic.
// 'cents' is an explicit legacy/synthetic adapter unit, not an assumed live API format.
export function normalizePrice(value, unit) {
  if (!['dollars', 'cents'].includes(unit)) throw new TypeError('Unknown price unit')
  if (value === null) return null // Missing quote is different from a real zero price.
  if (typeof value !== 'string' || !/^\d+(\.\d+)?$/.test(value) || value.length > 80) {
    throw new TypeError('Price must be a bounded unsigned decimal string or null')
  }
  const [whole, fraction = ''] = value.split('.')
  const numerator = BigInt(whole + fraction) * 1_000_000n
  const denominator = 10n ** BigInt(fraction.length) * (unit === 'cents' ? 100n : 1n)
  if (numerator > denominator * 1_000_000n) throw new RangeError('Price exceeds $1 face value')
  if (numerator % denominator !== 0n) throw new RangeError('Price needs more than six decimal places')
  return (numerator / denominator).toString()
}

export function normalizeRecord(input) {
  const venue = nonempty(input.venue, 'venue')
  const marketId = nonempty(input.marketId, 'marketId')
  const outcomeId = nonempty(input.outcomeId, 'outcomeId')
  if (!['condition_true', 'condition_false'].includes(input.canonicalOutcome)) throw new TypeError('Explicit outcome mapping required')
  if (!['bid', 'ask', 'last', 'midpoint'].includes(input.quoteKind)) throw new TypeError('Explicit quote kind required')
  if (!['open', 'closed', 'resolved', 'unknown'].includes(input.status)) throw new TypeError('Explicit adapter status required')
  return {
    key: JSON.stringify([venue, marketId, outcomeId]), // No collisions from punctuation in IDs.
    venue, marketId, outcomeId,
    canonicalOutcome: input.canonicalOutcome,
    quoteKind: input.quoteKind,
    priceMicros: normalizePrice(input.price, input.priceUnit),
    sourceAt: timestamp(input.sourceAt, 'sourceAt', true),
    receivedAt: timestamp(input.receivedAt, 'receivedAt'),
    closeAt: timestamp(input.closeAt, 'closeAt', true),
    resolvedAt: timestamp(input.resolvedAt, 'resolvedAt', true),
    status: input.status,
    rawStatus: nonempty(input.rawStatus, 'rawStatus'),
    // A teaching flag cannot replace an authenticated, versioned rule-review registry.
    terms: input.terms ? { ...input.terms } : null,
  }
}

const TERM_FIELDS = ['subject', 'predicate', 'observationAt', 'resolutionSource', 'voidRule', 'payoutTerms']

export function compareContracts(left, right) {
  const reasons = []
  if (left.canonicalOutcome !== right.canonicalOutcome) reasons.push('Different outcome mapping')
  for (const [label, record] of [['left', left], ['right', right]]) {
    if (record.terms?.reviewed !== true) reasons.push(`${label}: terms have not been reviewed`)
    for (const field of TERM_FIELDS) {
      if (typeof record.terms?.[field] !== 'string' || !record.terms[field].trim()) reasons.push(`${label}: missing ${field}`)
    }
  }
  for (const field of TERM_FIELDS) {
    if (left.terms?.[field] !== right.terms?.[field]) reasons.push(`Different ${field}`)
  }
  // Conservative gate: differing close times require review even if the event is the same.
  if (left.closeAt === null || right.closeAt === null || left.closeAt !== right.closeAt) reasons.push('Close times require review')
  return { equivalent: reasons.length === 0, reasons }
}

export function quoteFreshness(record, now, maxAgeMs) {
  timestamp(now, 'now')
  if (!Number.isSafeInteger(maxAgeMs) || maxAgeMs < 0) throw new TypeError('Invalid maximum age')
  if (record.priceMicros === null || record.sourceAt === null) return 'missing'
  const received = Date.parse(record.receivedAt)
  const source = Date.parse(record.sourceAt)
  const current = Date.parse(now)
  if (source > current || received > current || source > received) return 'clock-review'
  return current - source > maxAgeMs ? 'stale' : 'fresh'
}

export function demoRecords() {
  const common = {
    marketId: 'demo-market-900719925474099312345', outcomeId: 'demo-yes',
    canonicalOutcome: 'condition_true', quoteKind: 'bid', priceUnit: 'dollars',
    sourceAt: '2026-10-01T12:00:00.000Z', receivedAt: '2026-10-01T12:00:01.000Z',
    closeAt: '2026-10-30T23:00:00.000Z', resolvedAt: null, status: 'open', rawStatus: 'adapter-demo-open',
    terms: { reviewed: true, subject: 'Fictional Example Index', predicate: 'index > 100',
      observationAt: '2026-10-31T00:00:00.000Z', resolutionSource: 'Example Authority A',
      voidRule: 'void if official observation is unavailable', payoutTerms: 'USD 1 per winning contract' },
  }
  return [
    normalizeRecord({ ...common, venue: 'demo-venue-a', price: '0.615' }),
    normalizeRecord({ ...common, venue: 'demo-venue-b', price: '0.6150',
      terms: { ...common.terms, resolutionSource: 'Example Authority B' } }),
  ]
}

if (process.argv[1] && import.meta.url === pathToFileURL(process.argv[1]).href) {
  const [left, right] = demoRecords()
  console.log(JSON.stringify({ prices: [left.priceMicros, right.priceMicros], comparison: compareContracts(left, right) }, null, 2))
}