text: import { 
          RECEIVE_TWEETS,
          TOGGLE_TWEET,
          ADD_TWEET,
      } from '../actions/tweets';
  
  export function tweets (state={}, action) {
      switch (action.type) {
          case RECEIVE_TWEETS:
              return {
                  ...state,
                  ...action.tweets
              }
          case TOGGLE_TWEET:
              return {
                  ...state,
                  [action.id]: {
                      ...state[action.id],
                      likes: action.hasLiked === true
                          ? state[action.id].likes.filter((uID)=> uID !== action.authedUser)
                          : state[action.id].likes.concat([action.authedUser]),
                  }
              }
          case ADD_TWEET:
              const { tweet } = action;
  
              let replyingTo = {};
  
              if (tweet.replyingTo !== null) {
                  replyingTo = {
                      [tweet.replyingTo]: {
                          ...state[tweet.replyingTo],
                          replies: state[tweet.replyingTo].replies.concat([tweet.id])
                      }
                  }
              }
  
              return {
                  ...state,
                  [action.tweet.id]: action.tweet,
                  ...replyingTo,
              }
          default: 
              return state;    
      }
  }