bigbuffet-rw/app/soapbox/reducers/trends.js

import { Map as ImmutableMap, List as ImmutableList, fromJS } from 'immutable';

import {
  TRENDS_FETCH_REQUEST,
  TRENDS_FETCH_SUCCESS,
  TRENDS_FETCH_FAIL,
} from '../actions/trends';

const initialState = ImmutableMap({
  items: ImmutableList(),
  isLoading: false,
});

export default function trendsReducer(state = initialState, action) {
  switch (action.type) {
    case TRENDS_FETCH_REQUEST:
      return state.set('isLoading', true);
    case TRENDS_FETCH_SUCCESS:
      return state.withMutations(map => {
        map.set('items', fromJS(action.tags.map((x => x))));
        map.set('isLoading', false);
      });
    case TRENDS_FETCH_FAIL:
      return state.set('isLoading', false);
    default:
      return state;
  }
}