redux-crud-store/src/cachePeriod.js

Store of server-side models for Redux single page applications

import devMessage from './devMessage'

const TEN_MINUTES = 10 * 60 * 1000

function getCachePeriod({ showMessages } = {}) {
  let value = process.env.CACHE_PERIOD ||
    process.env.REACT_APP_CACHE_PERIOD ||
    TEN_MINUTES
  value = Math.round(value)
  if (isNaN(value)) {
    value = TEN_MINUTES
    if (showMessages) {
      devMessage('getCachePeriod got NaN! Falling back to ten minute cache period')
    }
  }
  if (value < 1000) {
    value = TEN_MINUTES
    if (showMessages) {
      devMessage(`getCachePeriod got a value under one second!
                  Falling back to ten minute cache period`)
    }
  }
  return value
}

function getHalfCachePeriod() {
  let value = process.env.HALF_CACHE_PERIOD ||
    process.env.REACT_APP_HALF_CACHE_PERIOD ||
    getCachePeriod() / 2
  value = Math.round(value)
  if (isNaN(value)) {
    value = Math.round(getCachePeriod({ showMessages: false }) / 2)
    devMessage(`getHalfCachePeriod got NaN! Falling back to half of cachePeriod: ${value}`)
  }
  if (value < 500) {
    value = Math.round(getCachePeriod({ showMessages: false }) / 2)
    devMessage(`getHalfCachePeriod got a value under 500ms!
                Falling back to half of cache period: ${value}`)
  }
  return value
}

const cachePeriod = getCachePeriod()
const halfCachePeriod = getHalfCachePeriod()

function cachePeriodAgo(now, customCachePeriod = undefined) {
  const actualCachePeriod = customCachePeriod || cachePeriod
  return now - actualCachePeriod
}

// public
export { cachePeriodAgo, cachePeriod, halfCachePeriod }

// only visible for testing
export { getCachePeriod, getHalfCachePeriod }