gistfile1.txt

  function prepareFee(): Promise<Object> {
    const multiplier = instructions.signersCount === undefined ? 1 :
      instructions.signersCount + 1
    if (instructions.fee !== undefined) {
      txJSON.Fee = scaleValue(common.xrpToDrops(instructions.fee), multiplier)
      return Promise.resolve(txJSON)
    }
    const cushion = api._feeCushion
    return common.serverInfo.getFee(api.connection, cushion).then(fee => {
      return api.connection.getFeeRef().then(feeRef => {
        const extraFee =
          (txJSON.TransactionType !== 'EscrowFinish' ||
            txJSON.Fulfillment === undefined) ? 0 :
          (cushion * feeRef * (32 + Math.floor(
            new Buffer(txJSON.Fulfillment, 'hex').length / 16)))
        const feeDrops = common.xrpToDrops(fee)
        if (instructions.maxFee !== undefined) {
          const maxFeeDrops = common.xrpToDrops(instructions.maxFee)
          const normalFee = scaleValue(feeDrops, multiplier, extraFee)
          txJSON.Fee = BigNumber.min(normalFee, maxFeeDrops).toString();
        } else {
          txJSON.Fee = scaleValue(feeDrops, multiplier, extraFee)
        }
        return txJSON
      })
    })
  }