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

describe('combinations', function () {
  it('should calculate the combinations of a number taking k at a time', function () {
    assert.strictEqual(combinations(0, 0), 1)
    assert.strictEqual(combinations(7, 5), 21)
    assert.strictEqual(combinations(20, 15), 15504)
    assert.strictEqual(combinations(63, 7), 553270671)
    assert.strictEqual(combinations(25, 6), 177100)
  })

  it('should calculate the combinations of n items taken k at a time with BigNumbers', function () {
    assert.deepStrictEqual(combinations(math.bignumber(7), math.bignumber(5)), math.bignumber(21))
    assert.deepStrictEqual(combinations(math.bignumber(20), math.bignumber(15)), math.bignumber(15504))
    assert.deepStrictEqual(combinations(math.bignumber(63), math.bignumber(7)), math.bignumber(553270671))
    assert.deepStrictEqual(combinations(math.bignumber(25), math.bignumber(6)), math.bignumber(177100))
  })

  it('should not work with non-integer and negative input', function () {
    assert.throws(function () { combinations(-12, 6) }, TypeError)
    assert.throws(function () { combinations(12, -6) }, TypeError)
    assert.throws(function () { combinations(0.5, 3) }, TypeError)
    assert.throws(function () { combinations(4, 0.5) }, TypeError)
    assert.throws(function () { combinations(3, 5) }, TypeError)
    assert.throws(function () { combinations(math.bignumber(3), math.bignumber(5)) }, TypeError)
    assert.throws(function () { combinations(math.bignumber(3.5), math.bignumber(-3)) }, TypeError)
    assert.throws(function () { combinations(math.bignumber(3.5), 1 / 3) }, TypeError)
  })

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

  it('should LaTeX combinations', function () {
    const expression = math.parse('combinations(3,2)')
    assert.strictEqual(expression.toTex(), '\\binom{3}{2}')
  })
})