accounts-frontend/packages/app/components/user/reducer.ts

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

export interface User {
    id: number | null;
    uuid: string | null;
    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;
};

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: any }) {
    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,
                }
            );
    }
}