/**
 * lodash 3.0.0 (Custom Build) <https://lodash.com/>
 * Build: `lodash modern modularize exports="npm" -o ./`
 * Copyright 2012-2015 The Dojo Foundation <http://dojofoundation.org/>
 * Based on Underscore.js 1.7.0 <http://underscorejs.org/LICENSE>
 * Copyright 2009-2015 Jeremy Ashkenas, DocumentCloud and Investigative Reporters & Editors
 * Available under MIT license <https://lodash.com/license>
 */
var baseCallback = require('lodash._basecallback'),
    baseEach = require('lodash._baseeach'),
    baseReduce = require('lodash._basereduce'),
    isArray = require('lodash.isarray');

/**
 * A specialized version of `_.reduce` for arrays without support for callback
 * shorthands or `this` binding.
 *
 * @private
 * @param {Array} array The array to iterate over.
 * @param {Function} iteratee The function invoked per iteration.
 * @param {*} [accumulator] The initial value.
 * @param {boolean} [initFromArray] Specify using the first element of `array`
 *  as the initial value.
 * @returns {*} Returns the accumulated value.
 */
function arrayReduce(array, iteratee, accumulator, initFromArray) {
  var index = -1,
      length = array.length;

  if (initFromArray && length) {
    accumulator = array[++index];
  }
  while (++index < length) {
    accumulator = iteratee(accumulator, array[index], index, array);
  }
  return accumulator;
}

/**
 * Reduces `collection` to a value which is the accumulated result of running
 * each element in `collection` through `iteratee`, where each successive
 * invocation is supplied the return value of the previous. If `accumulator`
 * is not provided the first element of `collection` is used as the initial
 * value. The `iteratee` is bound to `thisArg`and invoked with four arguments;
 * (accumulator, value, index|key, collection).
 *
 * Many lodash methods are guarded to work as interatees for methods like
 * `_.reduce`, `_.reduceRight`, and `_.transform`.
 *
 * The guarded methods are:
 * `assign`, `defaults`, `merge`, and `sortAllBy`
 *
 * @static
 * @memberOf _
 * @alias foldl, inject
 * @category Collection
 * @param {Array|Object|string} collection The collection to iterate over.
 * @param {Function} [iteratee=_.identity] The function invoked per iteration.
 * @param {*} [accumulator] The initial value.
 * @param {*} [thisArg] The `this` binding of `iteratee`.
 * @returns {*} Returns the accumulated value.
 * @example
 *
 * _.reduce([1, 2], function(sum, n) {
 *   return sum + n;
 * });
 * // => 3
 *
 * _.reduce({ 'a': 1, 'b': 2 }, function(result, n, key) {
 *   result[key] = n * 3;
 *   return result;
 * }, {});
 * // => { 'a': 3, 'b': 6 } (iteration order is not guaranteed)
 */
function reduce(collection, iteratee, accumulator, thisArg) {
  var func = isArray(collection) ? arrayReduce : baseReduce;
  return func(collection, baseCallback(iteratee, thisArg, 4), accumulator, arguments.length < 3, baseEach);
}

module.exports = reduce;