import utils from '../../../../scoring/utils'
import {
  START_UPPER,
  END_UPPER,
  ALL_UPPER_INVERTED,
  ALL_LOWER_INVERTED,
  ONE_LOWER,
  ONE_UPPER,
  ALPHA_INVERTED,
} from '../../../../data/const'

const getVariations = (cleanedWord: string) => {
  const wordArray = cleanedWord.split('')
  const upperCaseCount = wordArray.filter((char) =>
    char.match(ONE_UPPER),
  ).length
  const lowerCaseCount = wordArray.filter((char) =>
    char.match(ONE_LOWER),
  ).length

  let variations = 0
  const variationLength = Math.min(upperCaseCount, lowerCaseCount)
  for (let i = 1; i <= variationLength; i += 1) {
    variations += utils.nCk(upperCaseCount + lowerCaseCount, i)
  }
  return variations
}

export default (word: string) => {
  // clean words of non alpha characters to remove the reward effekt to capitalize the first letter https://github.com/dropbox/zxcvbn/issues/232
  const cleanedWord = word.replace(ALPHA_INVERTED, '')
  if (
    cleanedWord.match(ALL_LOWER_INVERTED) ||
    cleanedWord.toLowerCase() === cleanedWord
  ) {
    return 1
  }
  // a capitalized word is the most common capitalization scheme,
  // so it only doubles the search space (uncapitalized + capitalized).
  // all caps and end-capitalized are common enough too, underestimate as 2x factor to be safe.
  const commonCases = [START_UPPER, END_UPPER, ALL_UPPER_INVERTED]
  const commonCasesLength = commonCases.length
  for (let i = 0; i < commonCasesLength; i += 1) {
    const regex = commonCases[i]
    if (cleanedWord.match(regex)) {
      return 2
    }
  }

  // otherwise calculate the number of ways to capitalize U+L uppercase+lowercase letters
  // with U uppercase letters or less. or, if there's more uppercase than lower (for eg. PASSwORD),
  // the number of ways to lowercase U+L letters with L lowercase letters or less.
  return getVariations(cleanedWord)
}