HORIZON PROJECT

var baseRest = require('./_baseRest'),

    createWrap = require('./_createWrap'),

    getHolder = require('./_getHolder'),

    replaceHolders = require('./_replaceHolders');

/** Used to compose bitmasks for function metadata. */

var WRAP_BIND_FLAG = 1,

    WRAP_BIND_KEY_FLAG = 2,

    WRAP_PARTIAL_FLAG = 32;

/**

 * Creates a function that invokes the method at `object[key]` with `partials`

 * prepended to the arguments it receives.

 *

 * This method differs from `_.bind` by allowing bound functions to reference

 * methods that may be redefined or don't yet exist. See

 * [Peter Michaux's article](http://peter.michaux.ca/articles/lazy-function-definition-pattern)

 * for more details.

 *

 * The `_.bindKey.placeholder` value, which defaults to `_` in monolithic

 * builds, may be used as a placeholder for partially applied arguments.

 *

 * @static

 * @memberOf _

 * @since 0.10.0

 * @category Function

 * @param {Object} object The object to invoke the method on.

 * @param {string} key The key of the method.

 * @param {...*} [partials] The arguments to be partially applied.

 * @returns {Function} Returns the new bound function.

 * @example

 *

 * var object = {

 *   'user': 'fred',

 *   'greet': function(greeting, punctuation) {

 *     return greeting + ' ' + this.user + punctuation;

 *   }

 * };

 *

 * var bound = _.bindKey(object, 'greet', 'hi');

 * bound('!');

 * // => 'hi fred!'

 *

 * object.greet = function(greeting, punctuation) {

 *   return greeting + 'ya ' + this.user + punctuation;

 * };

 *

 * bound('!');

 * // => 'hiya fred!'

 *

 * // Bound with placeholders.

 * var bound = _.bindKey(object, 'greet', _, '!');

 * bound('hi');

 * // => 'hiya fred!'

 */

var bindKey = baseRest(function(object, key, partials) {

  var bitmask = WRAP_BIND_FLAG | WRAP_BIND_KEY_FLAG;

  if (partials.length) {

    var holders = replaceHolders(partials, getHolder(bindKey));

    bitmask |= WRAP_PARTIAL_FLAG;

  }

  return createWrap(key, bitmask, object, partials, holders);

});

// Assign default placeholders.

bindKey.placeholder = {};

module.exports = bindKey;