@walletfactory/emvqr/emvqr/emvqr.js

Decode emv qr code specification for payments

const crc = require('./crc')
const { getTag, getSubTag } = require('./scheme')

const validate = (text) => {
  const data = text.substring(0, text.length - 4)
  const checksum = text.substring(text.length - 4)

  const hash = crc.computeCRC(data)
  return hash === checksum
}

const read = (text, tagId) => {
  const id = text.substring(0, 2)
  const len = parseInt(text.substring(2, 4))
  const data = text.substring(4, len + 4)
  const next = text.substring(len + 4)

  if (!len || !data.length || len !== data.length) {
    return {}
  }

  if (!tagId && !getTag(id)) {
    return {}
  }

  if (tagId && !getSubTag(tagId, id)) {
    return {}
  }

  if (next.length) {
    let value = read(data, id)

    if (!Object.keys(value).length) {
      value = data
    }

    return {
      [id]: value,
      ...read(next)
    }
  }

  return { [id]: data }
}

const decode = (text) => {
  if (!validate(text)) {
    throw new Error('Checksum validation failed.')
  }

  return read(text)
}

module.exports = {
  decode
}