'use strict';

var typed = require('typed-function');
var collection = require('../../type/collection');
var add = require('../arithmetic/add');

/**
 * Compute the sum of a matrix or a list with values.
 * In case of a (multi dimensional) array or matrix, the sum of all
 * elements will be calculated.
 *
 * Syntax:
 *
 *     math.sum(a, b, c, ...)
 *     math.sum(A)
 *
 * Examples:
 *
 *     math.sum(2, 1, 4, 3);               // returns 10
 *     math.sum([2, 1, 4, 3]);             // returns 10
 *     math.sum([[2, 5], [4, 3], [1, 7]]); // returns 22
 *
 * See also:
 *
 *    mean, median, min, max, prod, std, var
 *
 * @param {... *} args  A single matrix or or multiple scalar values
 * @return {*} The sum of all values
 */
module.exports = typed('sum', {
  'Array | Matrix': function (args) {
    // sum([a, b, c, d, ...])
    return _sum(args);
  },

  'Array | Matrix, number': function () {
    // sum([a, b, c, d, ...], dim)
    // TODO: implement sum(A, dim)
    throw new Error('sum(A, dim) is not yet supported');
  },

  '...': function () {
    // sum(a, b, c, d, ...)
    return _sum(arguments);
  }
});

/**
 * Recursively calculate the sum of an n-dimensional array
 * @param {Array} array
 * @return {Number} sum
 * @private
 */
function _sum(array) {
  var sum = undefined;

  collection.deepForEach(array, function (value) {
    sum = (sum === undefined) ? value : add(sum, value);
  });

  if (sum === undefined) {
    throw new Error('Cannot calculate sum of an empty array');
  }
  return sum;
}