homework/chat-server/node_modules/tar/lib/update.js

'use strict'

// tar -u

const hlo = require('./high-level-opt.js')
const r = require('./replace.js')
// just call tar.r with the filter and mtimeCache

const u = module.exports = (opt_, files, cb) => {
  const opt = hlo(opt_)

  if (!opt.file)
    throw new TypeError('file is required')

  if (opt.gzip)
    throw new TypeError('cannot append to compressed archives')

  if (!files || !Array.isArray(files) || !files.length)
    throw new TypeError('no files or directories specified')

  files = Array.from(files)

  mtimeFilter(opt)
  return r(opt, files, cb)
}

const mtimeFilter = opt => {
  const filter = opt.filter

  if (!opt.mtimeCache)
    opt.mtimeCache = new Map()

  opt.filter = filter ? (path, stat) =>
    filter(path, stat) && !(opt.mtimeCache.get(path) > stat.mtime)
    : (path, stat) => !(opt.mtimeCache.get(path) > stat.mtime)
}