'use strict'

const flatten = require('../../utils/array').flatten

function factory (type, config, load, typed) {
  const MatrixIndex = load(require('../../type/matrix/MatrixIndex'))
  const concat = load(require('../matrix/concat'))
  const size = load(require('../matrix/size'))
  const subset = load(require('../matrix/subset'))
  const setDifference = load(require('../set/setDifference'))

  /**
   * Create the symmetric difference of two (multi)sets.
   * Multi-dimension arrays will be converted to single-dimension arrays before the operation.
   *
   * Syntax:
   *
   *    math.setSymDifference(set1, set2)
   *
   * Examples:
   *
   *    math.setSymDifference([1, 2, 3, 4], [3, 4, 5, 6])            // returns [1, 2, 5, 6]
   *    math.setSymDifference([[1, 2], [3, 4]], [[3, 4], [5, 6]])    // returns [1, 2, 5, 6]
   *
   * See also:
   *
   *    setUnion, setIntersect, setDifference
   *
   * @param {Array | Matrix}    a1  A (multi)set
   * @param {Array | Matrix}    a2  A (multi)set
   * @return {Array | Matrix}    The symmetric difference of two (multi)sets
   */
  const setSymDifference = typed('setSymDifference', {
    'Array | Matrix, Array | Matrix': function (a1, a2) {
      if (subset(size(a1), new MatrixIndex(0)) === 0) { // if any of them is empty, return the other one
        return flatten(a2)
      } else if (subset(size(a2), new MatrixIndex(0)) === 0) {
        return flatten(a1)
      }
      const b1 = flatten(a1)
      const b2 = flatten(a2)
      return concat(setDifference(b1, b2), setDifference(b2, b1))
    }
  })

  return setSymDifference
}

exports.name = 'setSymDifference'
exports.factory = factory