/**
  * @return int|null|void
  */
 protected function serve()
 {
     $package_file = $this->input->getArgument('package-file');
     $helper = $this->getHelper('question');
     $question = new ConfirmationQuestion('Are you sure you want to direct-install <cyan>' . $package_file . '</cyan> [y|N] ', false);
     $answer = $helper->ask($this->input, $this->output, $question);
     if (!$answer) {
         $this->output->writeln("exiting...");
         $this->output->writeln('');
         exit;
     }
     $tmp_dir = Grav::instance()['locator']->findResource('tmp://', true, true);
     $tmp_zip = $tmp_dir . '/Grav-' . uniqid();
     $this->output->writeln("");
     $this->output->writeln("Preparing to install <cyan>" . $package_file . "</cyan>");
     if ($this->isRemote($package_file)) {
         $zip = $this->downloadPackage($package_file, $tmp_zip);
     } else {
         $zip = $this->copyPackage($package_file, $tmp_zip);
     }
     if (file_exists($zip)) {
         $tmp_source = $tmp_dir . '/Grav-' . uniqid();
         $this->output->write("  |- Extracting package...    ");
         $extracted = Installer::unZip($zip, $tmp_source);
         if (!$extracted) {
             $this->output->write("\r");
             $this->output->writeln("  |- Extracting package...    <red>failed</red>");
             exit;
         }
         $this->output->write("\r");
         $this->output->writeln("  |- Extracting package...    <green>ok</green>");
         $type = $this->getPackageType($extracted);
         if (!$type) {
             $this->output->writeln("  '- <red>ERROR: Not a valid Grav package</red>");
             $this->output->writeln('');
             exit;
         }
         $blueprint = $this->getBlueprints($extracted);
         if ($blueprint) {
             if (isset($blueprint['dependencies'])) {
                 $depencencies = [];
                 foreach ($blueprint['dependencies'] as $dependency) {
                     if (is_array($dependency) && isset($dependency['name'])) {
                         $depencencies[] = $dependency['name'];
                     } else {
                         $depencencies[] = $dependency;
                     }
                 }
                 $this->output->writeln("  |- Dependencies found...    <cyan>[" . implode(',', $depencencies) . "]</cyan>");
                 $question = new ConfirmationQuestion("  |  '- Dependencies will not be satisfied. Continue ? [y|N] ", false);
                 $answer = $helper->ask($this->input, $this->output, $question);
                 if (!$answer) {
                     $this->output->writeln("exiting...");
                     $this->output->writeln('');
                     exit;
                 }
             }
         }
         if ($type == 'grav') {
             $this->output->write("  |- Checking destination...  ");
             Installer::isValidDestination(GRAV_ROOT . '/system');
             if (Installer::IS_LINK === Installer::lastErrorCode()) {
                 $this->output->write("\r");
                 $this->output->writeln("  |- Checking destination...  <yellow>symbolic link</yellow>");
                 $this->output->writeln("  '- <red>ERROR: symlinks found...</red> <yellow>" . GRAV_ROOT . "</yellow>");
                 $this->output->writeln('');
                 exit;
             }
             $this->output->write("\r");
             $this->output->writeln("  |- Checking destination...  <green>ok</green>");
             $this->output->write("  |- Installing package...  ");
             Installer::install($zip, GRAV_ROOT, ['sophisticated' => true, 'overwrite' => true, 'ignore_symlinks' => true], $extracted);
         } else {
             $name = $this->getPackageName($extracted);
             if (!$name) {
                 $this->output->writeln("<red>ERROR: Name could not be determined.</red> Please specify with --name|-n");
                 $this->output->writeln('');
                 exit;
             }
             $install_path = $this->getInstallPath($type, $name);
             $is_update = file_exists($install_path);
             $this->output->write("  |- Checking destination...  ");
             Installer::isValidDestination(GRAV_ROOT . DS . $install_path);
             if (Installer::lastErrorCode() == Installer::IS_LINK) {
                 $this->output->write("\r");
                 $this->output->writeln("  |- Checking destination...  <yellow>symbolic link</yellow>");
                 $this->output->writeln("  '- <red>ERROR: symlink found...</red>  <yellow>" . GRAV_ROOT . DS . $install_path . '</yellow>');
                 $this->output->writeln('');
                 exit;
             } else {
                 $this->output->write("\r");
                 $this->output->writeln("  |- Checking destination...  <green>ok</green>");
             }
             $this->output->write("  |- Installing package...  ");
             Installer::install($zip, GRAV_ROOT, ['install_path' => $install_path, 'theme' => $type == 'theme', 'is_update' => $is_update], $extracted);
         }
         Folder::delete($tmp_source);
         $this->output->write("\r");
         if (Installer::lastErrorCode()) {
             $this->output->writeln("  '- <red>Installation failed or aborted.</red>");
             $this->output->writeln('');
         } else {
             $this->output->writeln("  |- Installing package...    <green>ok</green>");
             $this->output->writeln("  '- <green>Success!</green>  ");
             $this->output->writeln('');
         }
     } else {
         $this->output->writeln("  '- <red>ERROR: ZIP package could not be found</red>");
     }
     Folder::delete($tmp_zip);
     // clear cache after successful upgrade
     $this->clearCache();
     return true;
 }