'use strict';

Object.defineProperty(exports, "__esModule", {
  value: true
});
exports.default = mapAsyncIterator;

var _iterall = require('iterall');

function _defineProperty(obj, key, value) { if (key in obj) { Object.defineProperty(obj, key, { value: value, enumerable: true, configurable: true, writable: true }); } else { obj[key] = value; } return obj; } /**
                                                                                                                                                                                                                   * Copyright (c) 2017-present, Facebook, Inc.
                                                                                                                                                                                                                   *
                                                                                                                                                                                                                   * This source code is licensed under the MIT license found in the
                                                                                                                                                                                                                   * LICENSE file in the root directory of this source tree.
                                                                                                                                                                                                                   *
                                                                                                                                                                                                                   * 
                                                                                                                                                                                                                   */

/**
 * Given an AsyncIterable and a callback function, return an AsyncIterator
 * which produces values mapped via calling the callback function.
 */
function mapAsyncIterator(iterable, callback, rejectCallback) {
  var iterator = (0, _iterall.getAsyncIterator)(iterable);
  var $return = void 0;
  var abruptClose = void 0;
  if (typeof iterator.return === 'function') {
    $return = iterator.return;
    abruptClose = function abruptClose(error) {
      var rethrow = function rethrow() {
        return Promise.reject(error);
      };
      return $return.call(iterator).then(rethrow, rethrow);
    };
  }

  function mapResult(result) {
    return result.done ? result : asyncMapValue(result.value, callback).then(iteratorResult, abruptClose);
  }

  var mapReject = void 0;
  if (rejectCallback) {
    // Capture rejectCallback to ensure it cannot be null.
    var reject = rejectCallback;
    mapReject = function mapReject(error) {
      return asyncMapValue(error, reject).then(iteratorResult, abruptClose);
    };
  }

  /* TODO: Flow doesn't support symbols as keys:
     https://github.com/facebook/flow/issues/3258 */
  return _defineProperty({
    next: function next() {
      return iterator.next().then(mapResult, mapReject);
    },
    return: function _return() {
      return $return ? $return.call(iterator).then(mapResult, mapReject) : Promise.resolve({ value: undefined, done: true });
    },
    throw: function _throw(error) {
      if (typeof iterator.throw === 'function') {
        return iterator.throw(error).then(mapResult, mapReject);
      }
      return Promise.reject(error).catch(abruptClose);
    }
  }, _iterall.$$asyncIterator, function () {
    return this;
  });
}

function asyncMapValue(value, callback) {
  return new Promise(function (resolve) {
    return resolve(callback(value));
  });
}

function iteratorResult(value) {
  return { value: value, done: false };
}