import { isNil } from '../is'

// @TODO need to finish `copy/`

/**
 * Creates an array of shuffled values, using a version of the
 * [Fisher-Yates shuffle](https://en.wikipedia.org/wiki/Fisher-Yates_shuffle).
 *
 * @since 0.1.0
 * @category Array
 *
 * @param {Array} array The array to shuffle.
 * @return {Array} Returns the new shuffled array.
 *
 * {@link https://github.com/lodash/lodash/blob/master/shuffle.js lodash-shuffle}
 * @see {@link lodash-shuffle}
 *
 * @example
 *
 *   shuffle([1, 2, 3, 4])
 *   //=> [4, 1, 3, 2]
 *
 */
function shuffle(array) {
  if (process.env.NODE_ENV !== 'production') {
    if (isNil(array)) {
      console.warn('do not shuffle an array that is nil', array)
      return []
    }
  }

  const length = array.length

  let index = -1
  const lastIndex = length - 1
  // @todo @@perf?
  // const result = copyArray(array)
  const result = [...array]

  while (++index < length) {
    const rand = index + Math.floor(Math.random() * (lastIndex - index + 1))
    const value = result[rand]
    result[rand] = result[index]
    result[index] = value
  }

  return result
}

export default shuffle