Login Controller for Laravel 5.3 which redirects user to where they were previously, or to the URL they we're trying to go to when they got redirected to the login page. Also allows Username or Email in the email field.

LoginController.php

<?php

namespace App\Http\Controllers\Auth;

use App\Http\Controllers\Controller;
use Illuminate\Foundation\Auth\AuthenticatesUsers;
use Illuminate\Http\Request;
use Illuminate\Routing\UrlGenerator;

class LoginController extends Controller
{
    /*
    |--------------------------------------------------------------------------
    | Login Controller
    |--------------------------------------------------------------------------
    |
    | This controller handles authenticating users for the application and
    | redirecting them to your home screen. The controller uses a trait
    | to conveniently provide its functionality to your applications.
    |
    */

    use AuthenticatesUsers;

    /**
     * Where to redirect users after login.
     *
     * @var string
     */
    protected $redirectTo = '/admin';

    /**
     * Create a new controller instance.
     *
     * @return void
     */
    public function __construct()
    {
        $this->middleware('guest', ['except' => 'logout']);
    }

    protected function credentials(Request $request)
    {
        $field = filter_var($request->input($this->username()), FILTER_VALIDATE_EMAIL) ? 'email' : 'name';
        $request->merge([$field => $request->input($this->username())]);
        return $request->only($field, 'password');
    }

    public function redirectTo()
    {

        $redirectTo = session('redirectTo');

        if( ! is_null( $redirectTo ) ) {
            session()->forget('redirectTo');
            return redirect($redirectTo);
        }

        return property_exists($this, 'redirectTo') ? $this->redirectTo : '/admin';

    }

    public function showLoginForm()
    {
        $previous = session('_previous');
        // dd($previous);
        $homeURL = url('/');
        if( isset( $previous['url'] ) ) {
            $previous = $previous['url'];
        } else {
            $previous = false;
        }

        if( $previous !== $homeURL and $previous !== $homeURL ) {
            session(['redirectTo' => $previous]);
        }
        return view('auth.login');
    }

}