/**
 * lodash (Custom Build) <https://lodash.com/>
 * Build: `lodash modularize exports="npm" -o ./`
 * Copyright 2012-2016 The Dojo Foundation <http://dojofoundation.org/>
 * Based on Underscore.js 1.8.3 <http://underscorejs.org/LICENSE>
 * Copyright 2009-2016 Jeremy Ashkenas, DocumentCloud and Investigative Reporters & Editors
 * Available under MIT license <https://lodash.com/license>
 */
var keys = require('lodash.keys');

/** `Object#toString` result references. */
var funcTag = '[object Function]',
    genTag = '[object GeneratorFunction]';

/**
 * A specialized version of `_.filter` for arrays without support for
 * iteratee shorthands.
 *
 * @private
 * @param {Array} array The array to iterate over.
 * @param {Function} predicate The function invoked per iteration.
 * @returns {Array} Returns the new filtered array.
 */
function arrayFilter(array, predicate) {
  var index = -1,
      length = array.length,
      resIndex = 0,
      result = [];

  while (++index < length) {
    var value = array[index];
    if (predicate(value, index, array)) {
      result[resIndex++] = value;
    }
  }
  return result;
}

/** Used for built-in method references. */
var objectProto = Object.prototype;

/**
 * Used to resolve the
 * [`toStringTag`](http://ecma-international.org/ecma-262/6.0/#sec-object.prototype.tostring)
 * of values.
 */
var objectToString = objectProto.toString;

/**
 * The base implementation of `_.functions` which creates an array of
 * `object` function property names filtered from `props`.
 *
 * @private
 * @param {Object} object The object to inspect.
 * @param {Array} props The property names to filter.
 * @returns {Array} Returns the function names.
 */
function baseFunctions(object, props) {
  return arrayFilter(props, function(key) {
    return isFunction(object[key]);
  });
}

/**
 * Checks if `value` is classified as a `Function` object.
 *
 * @static
 * @memberOf _
 * @since 0.1.0
 * @category Lang
 * @param {*} value The value to check.
 * @returns {boolean} Returns `true` if `value` is correctly classified,
 *  else `false`.
 * @example
 *
 * _.isFunction(_);
 * // => true
 *
 * _.isFunction(/abc/);
 * // => false
 */
function isFunction(value) {
  // The use of `Object#toString` avoids issues with the `typeof` operator
  // in Safari 8 which returns 'object' for typed array and weak map constructors,
  // and PhantomJS 1.9 which returns 'function' for `NodeList` instances.
  var tag = isObject(value) ? objectToString.call(value) : '';
  return tag == funcTag || tag == genTag;
}

/**
 * Checks if `value` is the
 * [language type](http://www.ecma-international.org/ecma-262/6.0/#sec-ecmascript-language-types)
 * of `Object`. (e.g. arrays, functions, objects, regexes, `new Number(0)`, and `new String('')`)
 *
 * @static
 * @memberOf _
 * @since 0.1.0
 * @category Lang
 * @param {*} value The value to check.
 * @returns {boolean} Returns `true` if `value` is an object, else `false`.
 * @example
 *
 * _.isObject({});
 * // => true
 *
 * _.isObject([1, 2, 3]);
 * // => true
 *
 * _.isObject(_.noop);
 * // => true
 *
 * _.isObject(null);
 * // => false
 */
function isObject(value) {
  var type = typeof value;
  return !!value && (type == 'object' || type == 'function');
}

/**
 * Creates an array of function property names from own enumerable properties
 * of `object`.
 *
 * @static
 * @since 0.1.0
 * @memberOf _
 * @category Object
 * @param {Object} object The object to inspect.
 * @returns {Array} Returns the function names.
 * @see _.functionsIn
 * @example
 *
 * function Foo() {
 *   this.a = _.constant('a');
 *   this.b = _.constant('b');
 * }
 *
 * Foo.prototype.c = _.constant('c');
 *
 * _.functions(new Foo);
 * // => ['a', 'b']
 */
function functions(object) {
  return object == null ? [] : baseFunctions(object, keys(object));
}

module.exports = functions;