import assert from 'assert'
import math from '../../../../src/bundleAny'
const composition = math.composition

describe('composition', function () {
  it('should calculate the number of ways to compose a set of n objects into k non-empty subsets', function () {
    assert.strictEqual(composition(5, 3), 6)
    assert.strictEqual(composition(1, 1), 1)
    assert.strictEqual(composition(8, 3), 21)
  })

  it('should calculate the composition of n items taken k at a time with BigNumbers', function () {
    assert.deepStrictEqual(composition(math.bignumber(7), math.bignumber(5)), math.bignumber(15))
    assert.deepStrictEqual(composition(math.bignumber(70), math.bignumber(3)), math.bignumber(2346))
    assert.deepStrictEqual(composition(math.bignumber(56), math.bignumber(11)), math.bignumber(29248649430))
  })

  it('should not work with non-integer and negative input', function () {
    assert.throws(function () { composition(0.5, 3) }, /TypeError: Positive integer value expected in function composition/)
    assert.throws(function () { composition(-2, 3) }, /TypeError: Positive integer value expected in function composition/)
    assert.throws(function () { composition(6, -2) }, /TypeError: Positive integer value expected in function composition/)
    assert.throws(function () { composition(3, 5) }, /TypeError: k must be less than or equal to n in function composition/)
    assert.throws(function () { composition(math.bignumber(3), math.bignumber(5)) }, /TypeError: k must be less than or equal to n in function composition/)
    assert.throws(function () { composition(math.bignumber(3.5), math.bignumber(-3)) }, /TypeError: Positive integer value expected in function composition/)
    assert.throws(function () { composition(math.bignumber(3.5), 0.25) }, /TypeError: Positive integer value expected in function composition/)
  })

  it('should not work with the wrong number or type of arguments', function () {
    assert.throws(function () { composition(5, 3, 2) })
    assert.throws(function () { composition(true, 'hello world') })
  })
})