HORIZON PROJECT

var apply = require('./_apply'),

    arrayMap = require('./_arrayMap'),

    baseIteratee = require('./_baseIteratee'),

    baseRest = require('./_baseRest');

/** Error message constants. */

var FUNC_ERROR_TEXT = 'Expected a function';

/**

 * Creates a function that iterates over `pairs` and invokes 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 _

 * @since 4.0.0

 * @category Util

 * @param {Array} pairs The predicate-function pairs.

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

 * @example

 *

 * var func = _.cond([

 *   [_.matches({ 'a': 1 }),           _.constant('matches A')],

 *   [_.conforms({ 'b': _.isNumber }), _.constant('matches B')],

 *   [_.stubTrue,                      _.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 == null ? 0 : pairs.length,

      toIteratee = baseIteratee;

  pairs = !length ? [] : arrayMap(pairs, function(pair) {

    if (typeof pair[1] != 'function') {

      throw new TypeError(FUNC_ERROR_TEXT);

    }

    return [toIteratee(pair[0]), pair[1]];

  });

  return baseRest(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;