'use strict';

var simpleIsEqual = function simpleIsEqual(a, b) {
  return a === b;
};

function index (resultFn, isEqual) {
  if (isEqual === void 0) {
    isEqual = simpleIsEqual;
  }

  var lastThis;
  var lastArgs = [];
  var lastResult;
  var calledOnce = false;

  var isNewArgEqualToLast = function isNewArgEqualToLast(newArg, index) {
    return isEqual(newArg, lastArgs[index]);
  };

  var result = function result() {
    for (var _len = arguments.length, newArgs = new Array(_len), _key = 0; _key < _len; _key++) {
      newArgs[_key] = arguments[_key];
    }

    if (calledOnce && lastThis === this && newArgs.length === lastArgs.length && newArgs.every(isNewArgEqualToLast)) {
      return lastResult;
    }

    lastResult = resultFn.apply(this, newArgs);
    calledOnce = true;
    lastThis = this;
    lastArgs = newArgs;
    return lastResult;
  };

  return result;
}

module.exports = index;