var baseEach = require('./baseEach');

/**
 * Gets the extremum value of `collection` invoking `iteratee` for each value
 * in `collection` to generate the criterion by which the value is ranked.
 * The `iteratee` is invoked with three arguments: (value, index|key, collection).
 *
 * @private
 * @param {Array|Object|string} collection The collection to iterate over.
 * @param {Function} iteratee The function invoked per iteration.
 * @param {Function} comparator The function used to compare values.
 * @param {*} exValue The initial extremum value.
 * @returns {*} Returns the extremum value.
 */
function baseExtremum(collection, iteratee, comparator, exValue) {
  var computed = exValue,
      result = computed;

  baseEach(collection, function(value, index, collection) {
    var current = +iteratee(value, index, collection);
    if (comparator(current, computed) || (current === exValue && current === result)) {
      computed = current;
      result = value;
    }
  });
  return result;
}

module.exports = baseExtremum;