bfx-api-node-util/lib/precision.js

Utilities for the Bitfinex node API

'use strict'

const Big = require('bignumber.js')

const DEFAULT_SIG_FIGS = 5
const PRICE_SIG_FIGS = 5
const AMOUNT_DECIMALS = 8

/**
 * Smartly set the precision (decimal) on a value based off of the significant
 * digit maximum. For example, calling with 3.34 when the max sig figs allowed
 * is 5 would return '3.3400', the representation number of decimals IF they
 * weren't zeros.
 *
 * @param {number} n
 * @param {number} maxSigs - default 5
 * @return {string} str
 */
const setSigFig = (number = 0, maxSigs = DEFAULT_SIG_FIGS) => {
  const n = +(number)
  if (!isFinite(n)) {
    return number
  }
  const value = n.toPrecision(maxSigs)

  return /e/.test(value)
    ? new Big(value).toString()
    : value
}

/**
 * Casts the provided value to a number if required, and limits the number of
 * decimals to the specified value. Returns a decimal string.
 *
 * @param {number|string} number
 * @param {number} decimals
 * @return {string} result
 */
const setPrecision = (number = 0, decimals = 0) => {
  const n = +(number)

  return (isFinite(n))
    ? n.toFixed(decimals)
    : number
}

/**
 * Prepares a amount for submitting via the API
 *
 * @param {number|string} amount
 * @return {string} preparedAmount
 */
const prepareAmount = (amount = 0) => {
  return setPrecision(amount, AMOUNT_DECIMALS)
}

/**
 * Prepares a price for submitting via the API
 *
 * @param {number|string} price
 * @return {string} preparedPrice
 */
const preparePrice = (price = 0) => {
  return setSigFig(price, PRICE_SIG_FIGS)
}

module.exports = {
  setSigFig, setPrecision, prepareAmount, preparePrice
}