@kyso/api/publish/utils/version-hash.js

const sha1 = require('hash.js/lib/hash/sha/1')
const Buffer = require('./buffer').Buffer

module.exports = (fileMap) => {
  // must add header which contains file names and message
  const hashes = Object.keys(fileMap)
  const filenames = Object.keys(fileMap)
    .map(key => fileMap[key])
    .sort()

  const header = `${filenames.join(',')}`
  const dataBufferList = hashes
    .sort() // <- NB since we need to versionHash to be the same every time
    .map(h => Buffer.from(h))

  const headerBuffer = Buffer.from(header)
  const buf = Buffer.concat(dataBufferList.concat(headerBuffer))
  return sha1().update(buf).digest('hex')
}