sniffix.js

//@ts-check
const util = require('util')
const fs = require('fs')
const path = require('path')
const writeFile = util.promisify(require('fs').writeFile)
const readFile = util.promisify(require('fs').readFile)

function createSniffer({ 
  fixtureDirectory,
  dummy = false
}) {
  
  if (dummy) {
    return function sniffDummy(_, fn) {
      return fn
    }
  }
  
  if (!fs.existsSync(fixtureDirectory)) {
    throw new Error('fixture directory must exist')
  }

  async function sniff(filename, fn) {
    const cacheFilePath = path.join(fixtureDirectory, filename + '.json',)
    if (fs.existsSync(cacheFilePath)) {
      const data = await readFile(cacheFilePath, 'utf8')
      if (data !== '') return JSON.parse(data)
    }
    const result = await fn()
    writeFile(cacheFilePath, JSON.stringify(result, null, 2))
    return result
  }
  sniff.off = function (filename, fn) {
    const cacheFilePath = path.join(fixtureDirectory, filename + '.json')
    writeFile(cacheFilePath, '', 'utf8')
    return sniff(cacheFilePath, fn)
  }
  return sniff
}



module.exports = createSniffer