settlement-header.js

import { decodePaymentResponseHeader } from '@x402/fetch'

const SETTLEMENT_HEADER_CANDIDATES = [
  'PAYMENT-RESPONSE',
  'X-PAYMENT-RESPONSE',
  'payment-response',
  'x-payment-response',
  'X402-PAYMENT-RESPONSE',
  'x402-payment-response',
]

function summarizeError(err) {
  return (err?.message || 'unknown error').substring(0, 180)
}

function safeJsonParse(value) {
  try {
    return JSON.parse(value)
  } catch {
    return null
  }
}

function safeBase64JsonParse(value) {
  try {
    const decoded = Buffer.from(value, 'base64').toString('utf8')
    return safeJsonParse(decoded)
  } catch {
    return null
  }
}

export function parseSettlementHeader(
  response,
  { decoder = decodePaymentResponseHeader, warn = console.warn } = {}
) {
  if (!response?.headers?.get) return null

  const candidates = SETTLEMENT_HEADER_CANDIDATES.map((name) => response.headers.get(name)).filter(
    Boolean
  )

  if (candidates.length === 0) return null

  let lastError = null
  for (const encoded of candidates) {
    const jsonDirect = safeJsonParse(encoded)
    if (jsonDirect) return jsonDirect

    try {
      const decoded = decoder(encoded)
      if (decoded) return decoded
    } catch (err) {
      lastError = err
      const fallbackJson = safeBase64JsonParse(encoded)
      if (fallbackJson) return fallbackJson
    }
  }

  warn(
    `  unable to decode payment response header, using unverified settlement mode: ${summarizeError(lastError)}`
  )
  return { unverified: true, _unverified: true }
}

export function extractTxHash(settle) {
  if (!settle || typeof settle !== 'object') return null
  return (
    settle.transaction ||
    settle.txHash ||
    settle.transactionHash ||
    settle.tx_id ||
    settle.txId ||
    null
  )
}