ArticleStore.js

// @flow
import {update} from "ramda";

import type {Article} from "../domain/Article";
import type {ArticleState} from "./ArticleState";

export type ArticleStore = {
  addArticle(article: Article): void;
  removeArticle(article: Article): void;
  updateArticle(article: Article): void;
  subscribe(subscriber: Function): Function;
  unsubscribe(subscriber: Function): void;
}

export const addArticle = (articleState: ArticleState, article: Article) => articleState.concat(article);

export const removeArticle = (articleState: ArticleState, article: Article) =>
  articleState.filter((a: Article) => a.id !== article.id);

export const updateArticle = (articleState: ArticleState, article: Article) => {
  const index = articleState.findIndex((a: Article) => a.id === article.id);
  return update(index, article, articleState);
};

export const subscribe = (subscribers: Function[], subscriber: Function) =>
  subscribers.concat(subscriber);

export const unsubscribe = (subscribers: Function[], subscriber: Function) =>
  subscribers.filter((s: Function) => s !== subscriber);

export const notify = (articleState: ArticleState, subscribers: Function[]) =>
  subscribers.forEach((s: Function) => s(articleState));

export const ArticleStoreFactory = (() => {
  let articleState: ArticleState = Object.freeze([]);
  let subscribers: Function[] = Object.freeze([]);

  return {
    addArticle: (article: Article) => {
      articleState = addArticle(articleState, article);
      notify(articleState, subscribers);
    },
    removeArticle: (article: Article) => {
      articleState = removeArticle(articleState, article);
      notify(articleState, subscribers);
    },
    updateArticle: (article: Article) => {
      articleState = updateArticle(articleState, article);
      notify(articleState, subscribers);
    },
    subscribe: (subscriber: Function) => {
      subscribers = subscribe(subscribers, subscriber);
      return subscriber;
    },
    unsubscribe: (subscriber: Function) => {
      subscribers = unsubscribe(subscribers, subscriber);
    }
  }
});

export const articleStore = ArticleStoreFactory();