// function utils

/*
 * Memoize a given function by caching the computed result.
 * The cache of a memoized function can be cleared by deleting the `cache`
 * property of the function.
 *
 * @param {function} fn                     The function to be memoized.
 *                                          Must be a pure function.
 * @param {function(args: Array)} [hasher]  A custom hash builder.
 *                                          Is JSON.stringify by default.
 * @return {function}                       Returns the memoized function
 */
exports.memoize = function(fn, hasher) {
  return function memoize() {
    if (typeof memoize.cache !== 'object') {
      memoize.cache = {};
    }

    var args = [];
    for (var i = 0; i < arguments.length; i++) {
      args[i] = arguments[i];
    }

    var hash = hasher ? hasher(args) : JSON.stringify(args);
    if (!(hash in memoize.cache)) {
      return memoize.cache[hash] = fn.apply(fn, args);
    }
    return memoize.cache[hash];
  };
};