/**
 * Checks if a given numeric value is a prime number.
 * This is any integer value divisible only by itself and 1.
 *
 * @function
 * @name isPrime
 * @param {number} val A value to verify is a prime number
 * @returns {boolean} Whether or not the given value is a prime number
 */
function isPrime(val) {
  if (!Number.isInteger(val) || val <= 1 || (val !== 2 && val % 2 === 0)) {
    return false
  }

  /* In checking if a given number is prime,
   * it isn't necessary to even check if it is
   * divisible by the majority of numbers between itself and 1.
   * Nothing greater than a third of the value need be checked,
   * but by getting a third/fourth/fifth/sixth/etc of the value
   * and using that as the cutoff limit to check for divisibility,
   * we can save many iterations.
   */
  let divideValBy = 3

  while (divideValBy < val && divideValBy <= (val / divideValBy)) {
    if (
      val % divideValBy === 0 || (
        Number.isInteger(val / divideValBy)
        && val % (val / divideValBy) === 0
      )
    ) {
      return false
    }

    divideValBy++
  }

  return true
}

export default isPrime