App.tsx

import React from 'react';

import {
  BrowserRouter,
  Route,
  Switch,
  Redirect
} from  'react-router-dom';

import Dashboard from './pages/dashboard'

import "@fortawesome/fontawesome-free/css/all.min.css";

import Auth from './lib/authentication';

interface AppState {
  authenticated?: boolean | null;
  email?: string;
}

interface AuthResponse {
  email: string;
}

class App extends React.Component<null, AppState> {
  constructor(props: any) {
    super(props);

    this.state = {
      authenticated: null
    };
  }

  public componentDidMount() {
    Auth.authenticateWithCookie()
    .then((response) => {
      response.json().then((resp: AuthResponse) => {
        this.setState({
          authenticated: true,
          email: resp.email
        });
      });
    })
    .catch(() => {
      this.setState({ authenticated: false });
    });
  }

  public render() {
    if (this.state.authenticated === null) {
      return null;
    } else if (this.state.authenticated === false) {
      return <Redirect to="/login" />;
    } else {
      return (
        <BrowserRouter>
          <Switch>
            <Route path="/dashboard" component={Dashboard} exact />

            <Redirect from="/" to="/dashboard" />
          </Switch>
        </BrowserRouter>
      );
    }
  }
}

export default App;