const mapAccum = require('../../../src/deps/loop/map/mapAcum')

describe('mapAccum', function() {
  var add = function(a, b) {
    return [a + b, a + b]
  }
  var mult = function(a, b) {
    return [a * b, a * b]
  }
  var concat = function(a, b) {
    return [a.concat(b), a.concat(b)]
  }

  it('map and accumulate simple functions over arrays with the supplied accumulator', function() {
    eq(mapAccum(add, 0, [1, 2, 3, 4]), [10, [1, 3, 6, 10]])
    eq(mapAccum(mult, 1, [1, 2, 3, 4]), [24, [1, 2, 6, 24]])
  })

  it('returns the list and accumulator for an empty array', function() {
    eq(mapAccum(add, 0, []), [0, []])
    eq(mapAccum(mult, 1, []), [1, []])
    eq(mapAccum(concat, [], []), [[], []])
  })

  it('is curried', function() {
    var addOrConcat = mapAccum(add)
    var sum = addOrConcat(0)
    var cat = addOrConcat('')
    eq(sum([1, 2, 3, 4]), [10, [1, 3, 6, 10]])
    eq(cat(['1', '2', '3', '4']), ['1234', ['1', '12', '123', '1234']])
  })

  it('correctly reports the arity of curried versions', function() {
    var sum = mapAccum(add, 0)
    eq(sum.length, 1)
  })
})