Exclude parent dirs

excludeParents.js

const assert = require('assert')

const isEqual = (a, b) => {
  if (a.length !== b.length) return false

  return a.every((aElem, index) => aElem === b[index])
}

// flip :: (a -> b -> c) -> (b -> a -> c)
const flip = (f) => (a, b) => f(b, a)

const isParent = (a, b) => {
  const aParts = a.split('/')
  const bParts = b.split('/')
  return isEqual(aParts, bParts.slice(0, aParts.length))
}
const isChild = flip(isParent)

assert(isParent('a/b', 'a/b/c'))
assert(!isParent('a/b', 'a/c/c'))
assert(isChild('a/b/c', 'a/b'))
assert(!isChild('a/b/c', 'a/c'))

const isParentOfAny = (dir, dirs) => (
  dirs.some((a) => (
    isParent(dir, a)
  ))
)

const withoutParentsOf = (dir, dirs) => (
  dirs.filter((a) => !isParent(a, dir))
)

const excludeParents = (dirs) => (
  dirs.reduce((acc, dir) => (
    (!isParentOfAny(dir, acc))
      ? withoutParentsOf(dir, acc).concat(dir)
      : acc
  ), [])
)

const resOne = excludeParents([
  'foo/bar/baz',
  'foo/bar',
  'foo/bar/baz/quix',
  'foo'
])

assert(
  (resOne[0] === 'foo/bar/baz/quix') &&
  (resOne.length === 1)
)
console.log('Test 1 a ok!')

const resTwo = excludeParents([
  'foo/bar/baz',
  'foo/bar',
  'foo',
  'bar',
  'bar/baz'
])

assert(
  (resTwo[0] === 'foo/bar/baz') &&
  (resTwo[1] === 'bar/baz') &&
  (resTwo.length === 2)
)
console.log('Test 2 a ok!')

const excludeParentsAlt = (dirs) => (
  dirs.sort().reduce((acc, dir) => {
    if (acc.length === 0) return [dir]

    if (isChild(dir, acc[acc.length - 1])) {
      return acc.slice(0, acc.length - 1).concat(dir)
    } else {
      return acc.concat(dir)
    }
  }, [])
)

const resThree = excludeParentsAlt([
  'foo/bar/baz',
  'foo/bar',
  'foo/bar/baz/quix',
  'foo'
])

assert(
  (resThree[0] === 'foo/bar/baz/quix') &&
  (resThree.length === 1)
)
console.log('Test 3 a ok!')

const resFour = excludeParentsAlt([
  'foo/bar/baz',
  'foo/bar',
  'foo',
  'bar',
  'bar/baz'
])

assert(
  (resFour[0] === 'bar/baz') &&
  (resFour[1] === 'foo/bar/baz') &&
  (resFour.length === 2)
)
console.log('Test 4 a ok!')