/**
 * lodash 4.2.1 (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 baseIteratee = require('lodash._baseiteratee'),
    rest = require('lodash.rest');

/** Used as the `TypeError` message for "Functions" methods. */
var FUNC_ERROR_TEXT = 'Expected a function';

/**
 * A faster alternative to `Function#apply`, this function invokes `func`
 * with the `this` binding of `thisArg` and the arguments of `args`.
 *
 * @private
 * @param {Function} func The function to invoke.
 * @param {*} thisArg The `this` binding of `func`.
 * @param {...*} args The arguments to invoke `func` with.
 * @returns {*} Returns the result of `func`.
 */
function apply(func, thisArg, args) {
  var length = args.length;
  switch (length) {
    case 0: return func.call(thisArg);
    case 1: return func.call(thisArg, args[0]);
    case 2: return func.call(thisArg, args[0], args[1]);
    case 3: return func.call(thisArg, args[0], args[1], args[2]);
  }
  return func.apply(thisArg, args);
}

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

  while (++index < length) {
    result[index] = iteratee(array[index], index, array);
  }
  return result;
}

/**
 * Creates a function that iterates over `pairs` invoking the corresponding
 * function of the first predicate to return truthy. The predicate-function
 * pairs are invoked with the `this` binding and arguments of the created
 * function.
 *
 * @static
 * @memberOf _
 * @category Util
 * @param {Array} pairs The predicate-function pairs.
 * @returns {Function} Returns the new function.
 * @example
 *
 * var func = _.cond([
 *   [_.matches({ 'a': 1 }),           _.constant('matches A')],
 *   [_.conforms({ 'b': _.isNumber }), _.constant('matches B')],
 *   [_.constant(true),                _.constant('no match')]
 * ]);
 *
 * func({ 'a': 1, 'b': 2 });
 * // => 'matches A'
 *
 * func({ 'a': 0, 'b': 1 });
 * // => 'matches B'
 *
 * func({ 'a': '1', 'b': '2' });
 * // => 'no match'
 */
function cond(pairs) {
  var length = pairs ? pairs.length : 0;

  pairs = !length ? [] : arrayMap(pairs, function(pair) {
    if (typeof pair[1] != 'function') {
      throw new TypeError(FUNC_ERROR_TEXT);
    }
    return [baseIteratee(pair[0]), pair[1]];
  });

  return rest(function(args) {
    var index = -1;
    while (++index < length) {
      var pair = pairs[index];
      if (apply(pair[0], this, args)) {
        return apply(pair[1], this, args);
      }
    }
  });
}

module.exports = cond;
