sententiaregum-flux-container/lib/util/createStoreRefreshStateHandler.js

The flux implementation of the sententiaregum project based on facebook/flux

/*
 * This file is part of the Sententiaregum project.
 *
 * (c) Maximilian Bosch <maximilian.bosch.27@gmail.com>
 * (c) Ben Bieler <benjaminbieler2014@gmail.com>
 *
 * For the full copyright and license information, please view the LICENSE
 * file that was distributed with this source code.
 */

'use strict';

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

var _events = require('events');

var _events2 = _interopRequireDefault(_events);

var _invariant = require('invariant');

var _invariant2 = _interopRequireDefault(_invariant);

function _interopRequireDefault(obj) { return obj && obj.__esModule ? obj : { default: obj }; }

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; }

/**
 * Handler which creates a callback that handles the state refresh of a store from a dispatcher
 * and flushes it into the view.
 *
 * @param {Function}        saveHandler The handler provided by the store to save all the data.
 * @param {EventEmitter}    emitter     The event emitter.
 * @param {Object.<String>} eventConfig The configuration of the event to handle.
 * @param {*}               oldState    The old state of the store.
 *
 * @returns {Function} The refreshing handler.
 * @private This is part of the internal API and should not be used directly!
 */
function createStoreRefreshStateHandler(saveHandler, emitter, eventConfig, oldState) {
  (0, _invariant2.default)(emitter instanceof _events2.default, 'The emitter must be an instance of node\'s core event emitter!');

  var modifySubsection = function modifySubsection(subsection, state, oldState) {
    return Object.assign({}, oldState, _defineProperty({}, subsection, Array.isArray(oldState[subsection]) && Array.isArray(state) ? oldState[subsection].concat(state) : state));
  };

  /**
   * Lightweight handler which evaluates the new state for a store based on the configuration for a store
   * and the dispatched payload.
   *
   * This function covers the following cases:
   * - an array with strings (modify a subsection of the current state snapshot) and handlers (modify the state with a function).
   * - no function (the payload will be interpreted as state).
   *
   * @param {*} state The newly dispatched payload.
   *
   * @returns {*} The evaluated result.
   */
  function handleState(state) {
    if (!eventConfig.function) {
      return state;
    }

    if (typeof eventConfig.function === 'function') {
      return eventConfig.function(state, oldState);
    }

    (0, _invariant2.default)(Array.isArray(eventConfig.function) && eventConfig.function.length > 0, 'The `function` value must be a non-empty array!');

    return eventConfig.function.reduce(function (prevState, handler) {
      if (typeof handler === 'function') {
        return handler(state, oldState);
      }

      return modifySubsection(handler, state, oldState);
    }, state);
  }

  return function (state) {
    return saveHandler(handleState(state), emitter);
  };
}