/**
 * 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'),
    isArray = require('lodash.isarray');

/**
 * Creates a `_.countBy`, `_.groupBy`, `_.indexBy`, or `_.partition` function.
 *
 * @private
 * @param {Function} setter The function to set keys and values of the accumulator object.
 * @param {Function} [initializer] The function to initialize the accumulator object.
 * @returns {Function} Returns the new aggregator function.
 */
function createAggregator(setter, initializer) {
  return function(collection, iteratee, thisArg) {
    var result = initializer ? initializer() : {};
    iteratee = baseCallback(iteratee, thisArg, 3);

    if (isArray(collection)) {
      var index = -1,
          length = collection.length;

      while (++index < length) {
        var value = collection[index];
        setter(result, value, iteratee(value, index, collection), collection);
      }
    } else {
      baseEach(collection, function(value, key, collection) {
        setter(result, value, iteratee(value, key, collection), collection);
      });
    }
    return result;
  };
}

module.exports = createAggregator;