'use strict'

const permutate = (aString) => {

if (typeof aString !== 'string' || !aString) {

throw new Error('The arg must be a valid, non empty string')

}

const characters = aString.split('')

let permutations = [[characters.shift()]]

while (characters.length) {

const currentCharacter = characters.shift()

permutations = calculateCurrentCharacterPermutation(

permutations,

currentCharacter

)

}

return permutations

.map((character) => character.join(''))

.filter((item, index, self) => self.indexOf(item) === index)

.sort()

}

const calculateCurrentCharacterPermutation = (

allPermutations,

currentCharacter

) => {

const currentPermutations = []

allPermutations.forEach((permutation) => {

let index = 0

while (index <= permutation.length) {

const tmp = [...permutation]

tmp.splice(index, 0, currentCharacter)

currentPermutations.push(tmp)

index++

}

})

return currentPermutations

}

export { permutate }