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export function getPosts(state) {
  const currentFilter = state.posts.currentFilter;
  const postsById = state.posts.postsById;
  const postsIdArray = currentFilter === 'all' ?
    _.keys(postsById) :
    _.filter(_.keys(postsById), (postId) => postsById[postId].topicUrl === currentFilter);
  return [postsById, postsIdArray];
}

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{
  "postsById": {
    "57jrtt": {
      "title": "My girlfriend left me because she couldn't handle my OCD.",
      "topicUrl": "/r/Jokes",
      "body": "I told her to close the door five times on her way out.",
    },
    "57l6oa": {
      "title": "Inception style vertical panoramas done with a quadcopter.",
      "topicUrl": "/r/pics",

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export function isTopicSelectionValid(state) {
  return state.topics.selectedTopicUrls.length === 3;
}

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export function selectTopic(topicUrl) {
  return (dispatch, getState) => {
    const selectedTopics = topicsSelectors.getSelectedTopicUrls(getState());
    if (_.indexOf(selectedTopics, topicUrl) !== -1) return;
    const newSelectedTopics = selectedTopics.length < 3 ?
      selectedTopics.concat(topicUrl) :
      selectedTopics.slice(1).concat(topicUrl);
    dispatch({ type: types.TOPICS_SELECTED, selectedTopicUrls: newSelectedTopics  });
  };
}

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import _ from 'lodash';

export default function reduce(state = initialState, action = {}) {
  // reducer implementation here
}

// selectors

export function getTopicsByUrl(state) {
  return state.topics.topicsByUrl;

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import React, { Component } from 'react';
import { connect } from 'react-redux';
import * as topicsActions from '../store/topics/actions';
import * as topicsSelectors from '../store/topics/reducer';

class TopicsScreen extends Component {
  // view implementation here
}

// which props do we want to inject, given the global store state?

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import * as types from './actionTypes';
import Immutable from 'seamless-immutable';

const initialState = Immutable({
  topicsByUrl: undefined,
  selectedTopicUrls: []
});

export default function reduce(state = initialState, action = {}) {
  switch (action.type) {

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import _ from 'lodash';
import * as types from './actionTypes';
import redditService from '../../services/reddit';

export function fetchTopics() {
  return async(dispatch, getState) => {
    try {
      const subredditArray = await redditService.getDefaultSubreddits();
      const topicsByUrl = _.keyBy(subredditArray, (subreddit) => subreddit.url);
      dispatch({ type: types.TOPICS_FETCHED, topicsByUrl });

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{
  "topicsByUrl": {
    "/r/Jokes/": {
      "title": "Jokes",
      "description": "The funniest sub on reddit. Hundreds of jokes posted each day, and some of them aren't even reposts! FarCraft"
    },
    "/r/pics/": {
      "title": "pics",
      "description": "I bet you can figure it out by reading the name of the subreddit"
    }

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import React from 'react';
import ReactDOM from 'react-dom';
import { createStore, applyMiddleware, combineReducers } from 'redux';
import { Provider } from 'react-redux';
import thunk from 'redux-thunk';
import App from './App';
import './index.css';

import * as reducers from './store/reducers';
const store = createStore(combineReducers(reducers), applyMiddleware(thunk));