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

describe('permutations', function () {
  it('should calculate the permutations of a number', function () {
    assert.strictEqual(permutations(0), 1)
    assert.strictEqual(permutations(1), 1)
    assert.strictEqual(permutations(2), 2)
    assert.strictEqual(permutations(3), 6)
    assert.strictEqual(permutations(4), 24)
    assert.strictEqual(permutations(5), 120)
  })

  it('should calculate the permutations of a BigNumber', function () {
    assert.deepStrictEqual(permutations(math.bignumber(4)), math.bignumber(24))
    assert.deepStrictEqual(permutations(math.bignumber(5)), math.bignumber(120))
    assert.deepStrictEqual(permutations(math.bignumber(8)), math.bignumber(40320))
  })

  it('should calculate the permutations of a BigNumber, taking k at a time', function () {
    assert.deepStrictEqual(permutations(math.bignumber(5), math.bignumber(4)), math.bignumber(120))
    assert.deepStrictEqual(permutations(math.bignumber(6), math.bignumber(3)), math.bignumber(120))
    assert.deepStrictEqual(permutations(math.bignumber(9), math.bignumber(8)), math.bignumber(362880))
  })

  it('should calculate the permutations of a number, taking k at a time', function () {
    assert.strictEqual(permutations(5, 4), 120)
    assert.strictEqual(permutations(9, 8), 362880)
    assert.strictEqual(permutations(7, 5), 2520)
  })

  it('should fail loudly when k is larger than x', function () {
    assert.throws(function () { permutations(5, 6) }, TypeError)
    assert.throws(function () { permutations(math.bignumber(5), math.bignumber(6)) }, TypeError)
  })

  it('should not accept negative or non-integer arguments', function () {
    assert.throws(function () { permutations(12, -6) }, TypeError)
    assert.throws(function () { permutations(-12, 6) }, TypeError)
    assert.throws(function () { permutations(4.5, 2) }, TypeError)
    assert.throws(function () { permutations(4, 0.5) }, TypeError)
    assert.throws(function () { permutations(math.bignumber(-12), -6) }, TypeError)
    assert.throws(function () { permutations(math.bignumber(12.5), math.bignumber(6)) }, TypeError)
    assert.throws(function () { permutations(math.bignumber(12.5), math.pi) }, TypeError)
  })

  it('should not accept more than two arguments', function () {
    assert.throws(function () { permutations(12, 6, 13) })
    assert.throws(function () { permutations(-12, 6, 13) })
  })

  it('should not accept arguments of the wrong type', function () {
    assert.throws(function () { permutations('baa baa black sheep', true) })
    assert.throws(function () { permutations(new Array(12)) })
  })

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