import assert from 'assert'
import math from '../../../../src/bundleAny'
const stirlingS2 = math.stirlingS2

describe('stirlingS2', function () {
  it('should calculate the number of ways to partition a set of n objects into k non-empty subsets', function () {
    assert.strictEqual(stirlingS2(5, 3), 25)
    assert.strictEqual(stirlingS2(0, 0), 1)
    assert.strictEqual(stirlingS2(8, 7), 28)
  })

  it('should calculate the stirlingS2 of n items taken k at a time with BigNumbers', function () {
    assert.deepStrictEqual(stirlingS2(math.bignumber(7), math.bignumber(5)), math.bignumber(140))
    assert.deepStrictEqual(stirlingS2(math.bignumber(8), math.bignumber(6)), math.bignumber(266))
  })

  it('should not work with non-integer and negative input', function () {
    assert.throws(function () { stirlingS2(0.5, 3) }, /Non-negative integer value expected/)
    assert.throws(function () { stirlingS2(-2, 3) }, /Non-negative integer value expected/)

    assert.throws(function () { stirlingS2(3, 5) }, /k must be less than or equal to n in function stirlingS2/)
    assert.throws(function () { stirlingS2(math.bignumber(3), math.bignumber(5)) }, /k must be less than or equal to n in function stirlingS2/)
    assert.throws(function () { stirlingS2(math.bignumber(3.5), math.bignumber(-3)) }, /Non-negative integer value expected/)
    assert.throws(function () { stirlingS2(math.bignumber(3.5), 1 / 3) }, /Non-negative integer value expected/)
  })

  it('should not work with the wrong number or type of arguments', function () {
    assert.throws(function () { stirlingS2(5, 3, 2) })
    assert.throws(function () { stirlingS2(true, 'hello world') })
  })

  it('should LaTeX stirlingS2', function () {
    const expression = math.parse('stirlingS2(3,2)')
    assert.strictEqual(expression.toTex(), '\\mathrm{S}\\left(3,2\\right)')
  })
})