fune/browser/components/newtab/content-src/lib/init-store.js

/* eslint-env mozilla/frame-script */

import {actionCreators as ac, actionTypes as at, actionUtils as au} from "common/Actions.jsm";
import {applyMiddleware, combineReducers, createStore} from "redux";

export const MERGE_STORE_ACTION = "NEW_TAB_INITIAL_STATE";
export const OUTGOING_MESSAGE_NAME = "ActivityStream:ContentToMain";
export const INCOMING_MESSAGE_NAME = "ActivityStream:MainToContent";
export const EARLY_QUEUED_ACTIONS = [at.SAVE_SESSION_PERF_DATA];

/**
 * A higher-order function which returns a reducer that, on MERGE_STORE action,
 * will return the action.data object merged into the previous state.
 *
 * For all other actions, it merely calls mainReducer.
 *
 * Because we want this to merge the entire state object, it's written as a
 * higher order function which takes the main reducer (itself often a call to
 * combineReducers) as a parameter.
 *
 * @param  {function} mainReducer reducer to call if action != MERGE_STORE_ACTION
 * @return {function}             a reducer that, on MERGE_STORE_ACTION action,
 *                                will return the action.data object merged
 *                                into the previous state, and the result
 *                                of calling mainReducer otherwise.
 */
function mergeStateReducer(mainReducer) {
  return (prevState, action) => {
    if (action.type === MERGE_STORE_ACTION) {
      return {...prevState, ...action.data};
    }

    return mainReducer(prevState, action);
  };
}

/**
 * messageMiddleware - Middleware that looks for SentToMain type actions, and sends them if necessary
 */
const messageMiddleware = store => next => action => {
  const skipLocal = action.meta && action.meta.skipLocal;
  if (au.isSendToMain(action)) {
    RPMSendAsyncMessage(OUTGOING_MESSAGE_NAME, action);
  }
  if (!skipLocal) {
    next(action);
  }
};

export const rehydrationMiddleware = store => next => action => {
  if (store._didRehydrate) {
    return next(action);
  }

  const isMergeStoreAction = action.type === MERGE_STORE_ACTION;
  const isRehydrationRequest = action.type === at.NEW_TAB_STATE_REQUEST;

  if (isRehydrationRequest) {
    store._didRequestInitialState = true;
    return next(action);
  }

  if (isMergeStoreAction) {
    store._didRehydrate = true;
    return next(action);
  }

  // If init happened after our request was made, we need to re-request
  if (store._didRequestInitialState && action.type === at.INIT) {
    return next(ac.AlsoToMain({type: at.NEW_TAB_STATE_REQUEST}));
  }

  if (au.isBroadcastToContent(action) || au.isSendToOneContent(action) || au.isSendToPreloaded(action)) {
    // Note that actions received before didRehydrate will not be dispatched
    // because this could negatively affect preloading and the the state
    // will be replaced by rehydration anyway.
    return null;
  }

  return next(action);
};

/**
 * This middleware queues up all the EARLY_QUEUED_ACTIONS until it receives
 * the first action from main. This is useful for those actions for main which
 * require higher reliability, i.e. the action will not be lost in the case
 * that it gets sent before the main is ready to receive it. Conversely, any
 * actions allowed early are accepted to be ignorable or re-sendable.
 */
export const queueEarlyMessageMiddleware = store => next => action => {
  if (store._receivedFromMain) {
    next(action);
  } else if (au.isFromMain(action)) {
    next(action);
    store._receivedFromMain = true;
    // Sending out all the early actions as main is ready now
    if (store._earlyActionQueue) {
      store._earlyActionQueue.forEach(next);
      store._earlyActionQueue = [];
    }
  } else if (EARLY_QUEUED_ACTIONS.includes(action.type)) {
    store._earlyActionQueue = store._earlyActionQueue || [];
    store._earlyActionQueue.push(action);
  } else {
    // Let any other type of action go through
    next(action);
  }
};

/**
 * initStore - Create a store and listen for incoming actions
 *
 * @param  {object} reducers An object containing Redux reducers
 * @param  {object} intialState (optional) The initial state of the store, if desired
 * @return {object}          A redux store
 */
export function initStore(reducers) {
  const store = createStore(
    mergeStateReducer(combineReducers(reducers)),
    global.RPMAddMessageListener && applyMiddleware(rehydrationMiddleware, queueEarlyMessageMiddleware, messageMiddleware)
  );

  store._didRehydrate = false;
  store._didRequestInitialState = false;

  if (global.RPMAddMessageListener) {
    global.RPMAddMessageListener(INCOMING_MESSAGE_NAME, msg => {
      try {
        store.dispatch(msg.data);
      } catch (ex) {
        console.error("Content msg:", msg, "Dispatch error: ", ex); // eslint-disable-line no-console
        dump(`Content msg: ${JSON.stringify(msg)}\nDispatch error: ${ex}\n${ex.stack}`);
      }
    });
  }

  return store;
}