/**
 * @module array-back
 * @example
 * const arrayify = require('array-back')
 */
module.exports = arrayify

/**
 * Takes any input and guarantees an array back.
 *
 * - converts array-like objects (e.g. `arguments`) to a real array
 * - converts `undefined` to an empty array
 * - converts any another other, singular value (including `null`) into an array containing that value
 * - ignores input which is already an array
 *
 * @param {*} - the input value to convert to an array
 * @returns {Array}
 * @alias module:array-back
 * @example
 * > a.arrayify(undefined)
 * []
 *
 * > a.arrayify(null)
 * [ null ]
 *
 * > a.arrayify(0)
 * [ 0 ]
 *
 * > a.arrayify([ 1, 2 ])
 * [ 1, 2 ]
 *
 * > function f(){ return a.arrayify(arguments); }
 * > f(1,2,3)
 * [ 1, 2, 3 ]
 */
function arrayify (input) {
  const t = require('typical')
  if (Array.isArray(input)) {
    return input
  } else {
    if (input === undefined) {
      return []
    } else if (t.isArrayLike(input)) {
      return Array.prototype.slice.call(input)
    } else {
      return [ input ]
    }
  }
}