import { Base64 } from 'js-base64'

export { textToBase64, base64ToText, isValidBase64, removePotentialDataAndMimePrefix }

function textToBase64(str: string, { makeUrlSafe = false }: { makeUrlSafe?: boolean } = {}) {
  const encoded = Base64.encode(str)
  return makeUrlSafe ? makeUriSafe(encoded) : encoded
}

function base64ToText(str: string, { makeUrlSafe = false }: { makeUrlSafe?: boolean } = {}) {
  if (!isValidBase64(str, { makeUrlSafe })) {
    throw new Error('Incorrect base64 string')
  }

  let cleanStr = removePotentialDataAndMimePrefix(str)
  if (makeUrlSafe) {
    cleanStr = unURI(cleanStr)
  }

  try {
    return Base64.decode(cleanStr)
  } catch {
    throw new Error('Incorrect base64 string')
  }
}

function removePotentialDataAndMimePrefix(str: string) {
  return str.replace(/^data:.*?;base64,/, '')
}

function isValidBase64(str: string, { makeUrlSafe = false }: { makeUrlSafe?: boolean } = {}) {
  let cleanStr = removePotentialDataAndMimePrefix(str)
  if (makeUrlSafe) {
    cleanStr = unURI(cleanStr)
  }

  try {
    const reEncodedBase64 = Base64.fromUint8Array(Base64.toUint8Array(cleanStr))
    if (makeUrlSafe) {
      return removePotentialPadding(reEncodedBase64) === cleanStr
    }
    return reEncodedBase64 === cleanStr.replace(/\s/g, '')
  } catch {
    return false
  }
}

function makeUriSafe(encoded: string) {
  return encoded.replace(/=/g, '').replace(/\+/g, '-').replace(/\//g, '_')
}

function unURI(encoded: string): string {
  return encoded
    .replace(/-/g, '+')
    .replace(/_/g, '/')
    .replace(/[^A-Za-z0-9+/]/g, '')
}

function removePotentialPadding(str: string) {
  return str.replace(/=/g, '')
}
