tokenSymbolResolver.js

// service responsible for resolving symbols to ethereum addresses
const rp = require('request-promise')

const { COINGECKO_API_URL, AIRSWAP_TOKEN_METADATA_URL } = require('./constants.js')
const jsonTokensBySymbol = require('./tokensBySymbol.json')

// Returns a promise that will always resolve()
// will resolve with a string `tokenAddress` or `undefined`
// e.g. tokenSymbolResolver('DAI') -> "0x89d24a6b4ccb1b6faa2625fe562bdd9a23260359"
// tokenSymbolResolver('FizzBuzz') -> undefined
const tokenSymbolResolver = async symbol => {
  let tokenAddress = null
  try {
    // first, query coingecko api and try to resolve dynamically
    tokenAddress = await new Promise(async (resolve, reject) => {
      const timeout = setTimeout(() => {
        reject(new Error('5s timeout reached waiting for Coingecko API'))
      }, 5000)

      try {
        // get all tokens and find by relevant symbol
        const cgTokensList = JSON.parse(await rp(`${COINGECKO_API_URL}/coins/list`))
        const matchedTokens = cgTokensList.filter(tokenObj => tokenObj.symbol.toUpperCase() === symbol.toUpperCase())
        if (matchedTokens.length === 0) throw new Error(`${symbol} not found in coingecko api`)

        // it's possible there could be multiple tokens that match the symbol
        // so we will return the one with the highest market cap between the group
        const bestTokenMetadataMatch = (await Promise.all(
          matchedTokens.map(obj => rp(`${COINGECKO_API_URL}/coins/${obj.id}`)),
        ))
          .map(JSON.parse)
          .reduce((a, b) => (a.market_cap_rank > b.market_cap_rank ? b : a))

        if (!bestTokenMetadataMatch.contract_address) throw new Error(`${symbol} not found in coingecko api`)

        // get decimals using airswap api
        const { decimals } = JSON.parse(
          await rp(`${AIRSWAP_TOKEN_METADATA_URL}/crawlTokenData?address=${bestTokenMetadataMatch.contract_address}`),
        )

        // resolve with token address and decimals
        resolve({ addr: bestTokenMetadataMatch.contract_address, decimals: parseInt(decimals, 10) })
      } catch (e) {
        reject(e)
      } finally {
        // clean up event loop
        global.clearTimeout(timeout)
      }
    })
  } catch (e) {
    console.log('error while resolving symbol with CoinGecko API:', e.message)
    console.log('falling back to static token metadata')
    tokenAddress = jsonTokensBySymbol[symbol]
  }

  return tokenAddress
}

module.exports = { tokenSymbolResolver }