var baseFlatten = require('./_baseFlatten'),
    map = require('./map');

/** Used as references for various `Number` constants. */
var INFINITY = 1 / 0;

/**
 * This method is like `_.flatMap` except that it recursively flattens the
 * mapped results.
 *
 * @static
 * @memberOf _
 * @since 4.7.0
 * @category Collection
 * @param {Array|Object} collection The collection to iterate over.
 * @param {Function} [iteratee=_.identity]
 *  The function invoked per iteration.
 * @returns {Array} Returns the new flattened array.
 * @example
 *
 * function duplicate(n) {
 *   return [[[n, n]]];
 * }
 *
 * _.flatMapDeep([1, 2], duplicate);
 * // => [1, 1, 2, 2]
 */
function flatMapDeep(collection, iteratee) {
  return baseFlatten(map(collection, iteratee), INFINITY);
}

module.exports = flatMapDeep;
