metamask-extension/ui/app/helpers/utils/gas-time-estimates.util.js

import BigNumber from 'bignumber.js'

export function newBigSigDig (n) {
  return new BigNumber((new BigNumber(String(n))).toPrecision(15))
}

const createOp = (a, b, op) => (newBigSigDig(a))[op](newBigSigDig(b))

export function bigNumMinus (a = 0, b = 0) {
  return createOp(a, b, 'minus')
}

export function bigNumDiv (a = 0, b = 1) {
  return createOp(a, b, 'div')
}

export function extrapolateY ({ higherY = 0, lowerY = 0, higherX = 0, lowerX = 0, xForExtrapolation = 0 }) {
  const slope = bigNumMinus(higherY, lowerY).div(bigNumMinus(higherX, lowerX))
  const newTimeEstimate = slope.times(bigNumMinus(higherX, xForExtrapolation)).minus(newBigSigDig(higherY)).negated()

  return newTimeEstimate.toNumber()
}

export function getAdjacentGasPrices ({ gasPrices, priceToPosition }) {
  const closestLowerValueIndex = gasPrices.findIndex((e, i, a) => e <= priceToPosition && a[i + 1] >= priceToPosition)
  const closestHigherValueIndex = gasPrices.findIndex((e) => e > priceToPosition)
  return {
    closestLowerValueIndex,
    closestHigherValueIndex,
    closestHigherValue: gasPrices[closestHigherValueIndex],
    closestLowerValue: gasPrices[closestLowerValueIndex],
  }
}

export function formatTimeEstimate (totalSeconds, greaterThanMax, lessThanMin) {
  const minutes = Math.floor(totalSeconds / 60)
  const seconds = Math.floor(totalSeconds % 60)

  if (!minutes && !seconds) {
    return '...'
  }

  let symbol = '~'
  if (greaterThanMax) {
    symbol = '< '
  } else if (lessThanMin) {
    symbol = '> '
  }

  const formattedMin = `${minutes ? minutes + ' min' : ''}`
  const formattedSec = `${seconds ? seconds + ' sec' : ''}`
  const formattedCombined = formattedMin && formattedSec
    ? `${symbol}${formattedMin} ${formattedSec}`
    : symbol + (formattedMin || formattedSec)

  return formattedCombined
}

export function getRawTimeEstimateData (currentGasPrice, gasPrices, estimatedTimes) {
  const minGasPrice = gasPrices[0]
  const maxGasPrice = gasPrices[gasPrices.length - 1]
  let priceForEstimation = currentGasPrice
  if (currentGasPrice < minGasPrice) {
    priceForEstimation = minGasPrice
  } else if (currentGasPrice > maxGasPrice) {
    priceForEstimation = maxGasPrice
  }

  const {
    closestLowerValueIndex,
    closestHigherValueIndex,
    closestHigherValue,
    closestLowerValue,
  } = getAdjacentGasPrices({ gasPrices, priceToPosition: priceForEstimation })

  const newTimeEstimate = extrapolateY({
    higherY: estimatedTimes[closestHigherValueIndex],
    lowerY: estimatedTimes[closestLowerValueIndex],
    higherX: closestHigherValue,
    lowerX: closestLowerValue,
    xForExtrapolation: priceForEstimation,
  })

  return {
    newTimeEstimate,
    minGasPrice,
    maxGasPrice,
  }
}

export function getRenderableTimeEstimate (currentGasPrice, gasPrices, estimatedTimes) {
  const {
    newTimeEstimate,
    minGasPrice,
    maxGasPrice,
  } = getRawTimeEstimateData(currentGasPrice, gasPrices, estimatedTimes)

  return formatTimeEstimate(newTimeEstimate, currentGasPrice > maxGasPrice, currentGasPrice < minGasPrice)
}