class Plugin

class Plugin implements PluginInterface, EventSubscriberInterface, Capable {
    
    /**
     * The Composer service.
     *
     * @var \Composer\Composer
     */
    protected $composer;
    
    /**
     * Composer's I/O service.
     *
     * @var \Composer\IO\IOInterface
     */
    protected $io;
    
    /**
     * The Composer Scaffold handler.
     *
     * @var \Drupal\Composer\Plugin\Scaffold\Handler
     */
    protected $handler;
    
    /**
     * Record whether the 'require' command was called.
     *
     * @var bool
     */
    protected $requireWasCalled;
    
    /**
     * {@inheritdoc}
     */
    public function activate(Composer $composer, IOInterface $io) {
        $this->composer = $composer;
        $this->io = $io;
        $this->requireWasCalled = FALSE;
    }
    
    /**
     * {@inheritdoc}
     */
    public function deactivate(Composer $composer, IOInterface $io) {
    }
    
    /**
     * {@inheritdoc}
     */
    public function uninstall(Composer $composer, IOInterface $io) {
    }
    
    /**
     * {@inheritdoc}
     */
    public function getCapabilities() {
        return [
            CommandProvider::class => ScaffoldCommandProvider::class,
        ];
    }
    
    /**
     * {@inheritdoc}
     */
    public static function getSubscribedEvents() {
        // Important note: We only instantiate our handler on "post" events.
        return [
            ScriptEvents::POST_UPDATE_CMD => 'postCmd',
            ScriptEvents::POST_INSTALL_CMD => 'postCmd',
            PackageEvents::POST_PACKAGE_INSTALL => 'postPackage',
            PluginEvents::COMMAND => 'onCommand',
        ];
    }
    
    /**
     * Post command event callback.
     *
     * @param \Composer\Script\Event $event
     *   The Composer event.
     */
    public function postCmd(Event $event) {
        $this->handler()
            ->scaffold();
    }
    
    /**
     * Post package event behavior.
     *
     * @param \Composer\Installer\PackageEvent $event
     *   Composer package event sent on install/update/remove.
     */
    public function postPackage(PackageEvent $event) {
        $this->handler()
            ->onPostPackageEvent($event);
    }
    
    /**
     * Pre command event callback.
     *
     * @param \Composer\Plugin\CommandEvent $event
     *   The Composer command event.
     */
    public function onCommand(CommandEvent $event) {
        if ($event->getCommandName() == 'require') {
            if ($this->handler) {
                throw new \Error('Core Scaffold Plugin handler instantiated too early. See https://www.drupal.org/project/drupal/issues/3104922');
            }
            $this->requireWasCalled = TRUE;
        }
    }
    
    /**
     * Instantiates the handler object upon demand.
     *
     * It is dangerous to update a Composer plugin if it loads any classes prior
     * to the `composer update` operation, and later tries to use them in a
     * post-update hook.
     */
    protected function handler() {
        if (!$this->handler) {
            $this->handler = new Handler($this->composer, $this->io);
            // On instantiation of our handler, notify it if the 'require' command
            // was executed.
            if ($this->requireWasCalled) {
                $this->handler
                    ->requireWasCalled();
            }
        }
        return $this->handler;
    }

}