'use strict';

Object.defineProperty(exports, "__esModule", {
  value: true
});
exports.createCombinations = void 0;

var _factory = require("../../utils/factory");

var _combinations = require("../../plain/number/combinations");

var name = 'combinations';
var dependencies = ['typed'];
var createCombinations =
/* #__PURE__ */
(0, _factory.factory)(name, dependencies, function (_ref) {
  var typed = _ref.typed;

  /**
   * Compute the number of ways of picking `k` unordered outcomes from `n`
   * possibilities.
   *
   * Combinations only takes integer arguments.
   * The following condition must be enforced: k <= n.
   *
   * Syntax:
   *
   *     math.combinations(n, k)
   *
   * Examples:
   *
   *    math.combinations(7, 5) // returns 21
   *
   * See also:
   *
   *    permutations, factorial
   *
   * @param {number | BigNumber} n    Total number of objects in the set
   * @param {number | BigNumber} k    Number of objects in the subset
   * @return {number | BigNumber}     Number of possible combinations.
   */
  return typed(name, {
    'number, number': _combinations.combinationsNumber,
    'BigNumber, BigNumber': function BigNumberBigNumber(n, k) {
      var BigNumber = n.constructor;
      var max, result, i, ii;
      var one = new BigNumber(1);

      if (!isPositiveInteger(n) || !isPositiveInteger(k)) {
        throw new TypeError('Positive integer value expected in function combinations');
      }

      if (k.gt(n)) {
        throw new TypeError('k must be less than n in function combinations');
      }

      max = n.minus(k);
      if (k.lt(max)) max = k;
      result = one;

      for (i = one, ii = n.minus(max); i.lte(ii); i = i.plus(1)) {
        result = result.times(max.plus(i)).dividedBy(i);
      }

      return result;
    } // TODO: implement support for collection in combinations

  });
});
/**
 * Test whether BigNumber n is a positive integer
 * @param {BigNumber} n
 * @returns {boolean} isPositiveInteger
 */

exports.createCombinations = createCombinations;

function isPositiveInteger(n) {
  return n.isInteger() && n.gte(0);
}