Check for license before the application loads in the browser

To achieve the functionality of checking the license before the application loads in the browser and periodically while the user is using the application, you can follow these steps:

1. Initial License Check on Application Load:

   • Perform the license check on the server side when the application first loads. This can be done in the entry point of your application, such as in the main controller or a specific route that serves the initial HTML.

2. Periodic License Check:

   • Use a background job or a scheduled task to periodically check the license validity. This can be done using a cron job or a task scheduler depending on the technology stack you are using.

3. Middleware for Periodic Checks:

   • While you mentioned that middleware is not ideal for checking the license on every request, you can still use middleware to perform periodic checks by setting a session or cache value that tracks the last check time.

Here is a sample implementation using Laravel (assuming you are using a PHP framework like Laravel):

Step 1: Initial License Check

In your main controller or route that serves the initial HTML:

// routes/web.php
Route::get('/', function () {
    // Perform the license check
    if (!checkLicense()) {
        abort(403, 'License is not valid.');
    }

    return view('welcome');
});

Step 2: Periodic License Check

Create a command to check the license and schedule it to run periodically:

// app/Console/Commands/CheckLicense.php
namespace App\Console\Commands;

use Illuminate\Console\Command;

class CheckLicense extends Command
{
    protected $signature = 'license:check';
    protected $description = 'Check if the license is still valid';

    public function handle()
    {
        if (!checkLicense()) {
            // Handle invalid license, e.g., log out users, disable features, etc.
            // This could involve setting a flag in the database or cache
        }
    }
}

Schedule this command in your Kernel.php:

// app/Console/Kernel.php
protected function schedule(Schedule $schedule)
{
    $schedule->command('license:check')->hourly();
}

Step 3: Middleware for Periodic Checks

Create middleware to check the license periodically:

// app/Http/Middleware/CheckLicenseMiddleware.php
namespace App\Http\Middleware;

use Closure;
use Illuminate\Support\Facades\Cache;

class CheckLicenseMiddleware
{
    public function handle($request, Closure $next)
    {
        $lastChecked = Cache::get('license_last_checked', 0);
        $now = now()->timestamp;

        // Check license every 30 minutes
        if ($now - $lastChecked > 1800) {
            if (!checkLicense()) {
                abort(403, 'License is not valid.');
            }
            Cache::put('license_last_checked', $now);
        }

        return $next($request);
    }
}

Register the middleware in your Kernel.php:

// app/Http/Kernel.php
protected $routeMiddleware = [
    // ...
    'check.license' => \App\Http\Middleware\CheckLicenseMiddleware::class,
];

Apply the middleware to your routes:

// routes/web.php
Route::middleware(['check.license'])->group(function () {
    Route::get('/dashboard', 'DashboardController@index');
    // other routes
});

Helper Function

Create a helper function to check the license:

// app/helpers.php
function checkLicense()
{
    $licenseKey = env('LICENSE_KEY');
    // Implement your license validation logic here
    // For example, decode and verify the protobuf signed key
    // Return true if valid, false otherwise
}

Make sure to autoload the helper file by adding it to composer.json:

"autoload": {
    "files": [
        "app/helpers.php"
    ]
}

Run composer dump-autoload to update the autoload files.

This setup ensures that the license is checked when the application first loads and periodically while the user is using the application, without sending license information to the browser.