efx-api-node/src/api/contract/approve.js

<img src="https://avatars3.githubusercontent.com/u/33315316?s=200&v=4" align="right" />

const reasons = require('../../lib/error/reasons')
/**
 * Approves a token for locking
 *
 */
module.exports = async (efx, token) => {
  const currency = efx.config['0x'].tokenRegistry[token]

  // REVIEW: 2 ** 256 -1 should be the max value for "uint"
  const amount = ((2 ** 256) - 1).toString(16)

  const args = [
    currency.wrapperAddress, // address _spender
    amount // uint amount
  ]

  // TODO: review error format
  if(token == 'USD' && (await efx.contract.isApproved(token) != 0)){
    return {
      error: 'ERR_TRADING_ETHFX_CANT_APPROVE_USDT_TWICE',
      reason: reasons.ERR_TRADING_ETHFX_CANT_APPROVE_USDT_TWICE.trim()
    }
  }

  if(token == 'ETH'){
    return {
      error: 'ERR_TRADING_ETHFX_APPROVE_ETH_NOT_REQUIRED',
      reason: reasons.ERR_TRADING_ETHFX_APPROVE_ETH_NOT_REQUIRED.trim()
    }
  }

  const action = 'approve'

  return efx.eth.send(
    efx.contract.abi.token,
    currency.tokenAddress,
    action,
    args
  )
}