/**
 * lodash 4.1.1 (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 createWrapper = require('lodash._createwrapper'),
    rest = require('lodash.rest');

/** Used to compose bitmasks for wrapper metadata. */
var PARTIAL_FLAG = 32;

/** Used as the internal argument placeholder. */
var PLACEHOLDER = '__lodash_placeholder__';

/**
 * Replaces all `placeholder` elements in `array` with an internal placeholder
 * and returns an array of their indexes.
 *
 * @private
 * @param {Array} array The array to modify.
 * @param {*} placeholder The placeholder to replace.
 * @returns {Array} Returns the new array of placeholder indexes.
 */
function replaceHolders(array, placeholder) {
  var index = -1,
      length = array.length,
      resIndex = -1,
      result = [];

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

/**
 * Gets the argument placeholder value for `func`.
 *
 * @private
 * @param {Function} func The function to inspect.
 * @returns {*} Returns the placeholder value.
 */
function getPlaceholder(func) {
  var object = func;
  return object.placeholder;
}

/**
 * Creates a function that invokes `func` with `partial` arguments prepended
 * to those provided to the new function. This method is like `_.bind` except
 * it does **not** alter the `this` binding.
 *
 * The `_.partial.placeholder` value, which defaults to `_` in monolithic
 * builds, may be used as a placeholder for partially applied arguments.
 *
 * **Note:** This method doesn't set the "length" property of partially
 * applied functions.
 *
 * @static
 * @memberOf _
 * @category Function
 * @param {Function} func The function to partially apply arguments to.
 * @param {...*} [partials] The arguments to be partially applied.
 * @returns {Function} Returns the new partially applied function.
 * @example
 *
 * var greet = function(greeting, name) {
 *   return greeting + ' ' + name;
 * };
 *
 * var sayHelloTo = _.partial(greet, 'hello');
 * sayHelloTo('fred');
 * // => 'hello fred'
 *
 * // Partially applied with placeholders.
 * var greetFred = _.partial(greet, _, 'fred');
 * greetFred('hi');
 * // => 'hi fred'
 */
var partial = rest(function(func, partials) {
  var holders = replaceHolders(partials, getPlaceholder(partial));
  return createWrapper(func, PARTIAL_FLAG, undefined, partials, holders);
});

// Assign default placeholders.
partial.placeholder = {};

module.exports = partial;