accounts-frontend/src/components/user/reducer.js

// @flow
import { UPDATE, SET, CHANGE_LANG } from './actions';

export type User = {|
  id: ?number,
  uuid: ?string,
  token: string,
  username: string,
  email: string,
  avatar: string,
  lang: string,
  isGuest: boolean,
  isActive: boolean,
  isOtpEnabled: boolean,
  passwordChangedAt: number,
  hasMojangUsernameCollision: boolean,
  maskedEmail?: string,
  shouldAcceptRules?: boolean,
|};

export type State = {
  user: User, // TODO: replace with centralized global state
};

const defaults: User = {
  id: null,
  uuid: null,
  username: '',
  token: '',
  email: '',
  // will contain user's email or masked email
  // (e.g. ex**ple@em*il.c**) depending on what information user have already provided
  maskedEmail: '',
  avatar: '',
  lang: '',
  isActive: false,
  isOtpEnabled: false,
  shouldAcceptRules: false, // whether user need to review updated rules
  passwordChangedAt: 0,
  hasMojangUsernameCollision: false,

  // frontend specific attributes
  isGuest: true,
};

export default function user(
  state: User = defaults,
  { type, payload }: { type: string, payload: ?Object },
) {
  switch (type) {
    case CHANGE_LANG:
      if (!payload || !payload.lang) {
        throw new Error('payload.lang is required for user reducer');
      }

      return {
        ...state,
        lang: payload.lang,
      };

    case UPDATE:
      if (!payload) {
        throw new Error('payload is required for user reducer');
      }

      return {
        ...state,
        ...payload,
      };

    case SET:
      payload = payload || {};

      return {
        ...defaults,
        ...payload,
      };

    default:
      return (
        state || {
          ...defaults,
        }
      );
  }
}