catstodon/app/assets/javascripts/components/reducers/relationships.jsx

import {
  ACCOUNT_FOLLOW_SUCCESS,
  ACCOUNT_UNFOLLOW_SUCCESS,
  ACCOUNT_BLOCK_SUCCESS,
  ACCOUNT_UNBLOCK_SUCCESS,
  RELATIONSHIPS_FETCH_SUCCESS
} from '../actions/accounts';
import Immutable from 'immutable';

const normalizeRelationship = (state, relationship) => state.set(relationship.get('id'), relationship);

const normalizeRelationships = (state, relationships) => {
  relationships.forEach(relationship => {
    state = normalizeRelationship(state, relationship);
  });

  return state;
};

const initialState = Immutable.Map();

export default function relationships(state = initialState, action) {
  switch(action.type) {
    case ACCOUNT_FOLLOW_SUCCESS:
    case ACCOUNT_UNFOLLOW_SUCCESS:
    case ACCOUNT_BLOCK_SUCCESS:
    case ACCOUNT_UNBLOCK_SUCCESS:
      return normalizeRelationship(state, Immutable.fromJS(action.relationship));
    case RELATIONSHIPS_FETCH_SUCCESS:
      return normalizeRelationships(state, Immutable.fromJS(action.relationships));
    default:
      return state;
  }
};