class ComposerPatchesValidator

final class ComposerPatchesValidator implements EventSubscriberInterface {
    use StringTranslationTrait;
    
    /**
     * The name of the plugin being analyzed.
     *
     * @var string
     */
    private const PLUGIN_NAME = 'cweagans/composer-patches';
    public function __construct(ModuleHandlerInterface $moduleHandler, ComposerInspector $composerInspector, PathLocator $pathLocator) {
    }
    
    /**
     * Validates the status of the patcher plugin.
     *
     * @param \Drupal\package_manager\Event\PreOperationStageEvent $event
     *   The event object.
     */
    public function validate(PreOperationStageEvent $event) : void {
        $messages = [];
        [
            $plugin_installed_in_active,
            $is_active_root_requirement,
            $active_configuration_ok,
        ] = $this->computePatcherStatus($this->pathLocator
            ->getProjectRoot());
        if ($event instanceof PreApplyEvent) {
            [
                $plugin_installed_in_stage,
                $is_stage_root_requirement,
                $stage_configuration_ok,
            ] = $this->computePatcherStatus($event->stage
                ->getStageDirectory());
            $has_staged_update = TRUE;
        }
        else {
            // No staged update exists.
            $has_staged_update = FALSE;
        }
        // If there's a staged update and the patcher has been installed or removed
        // in the stage directory, that's a problem.
        if ($has_staged_update && $plugin_installed_in_active !== $plugin_installed_in_stage) {
            if ($plugin_installed_in_stage) {
                $message = $this->t('It cannot be installed by Package Manager.');
            }
            else {
                $message = $this->t('It cannot be removed by Package Manager.');
            }
            $messages[] = $this->createErrorMessage($message, 'package-manager-faq-composer-patches-installed-or-removed');
        }
        // If the patcher is not listed in the runtime or dev dependencies, that's
        // an error as well.
        if ($plugin_installed_in_active && !$is_active_root_requirement || $has_staged_update && $plugin_installed_in_stage && !$is_stage_root_requirement) {
            $messages[] = $this->createErrorMessage($this->t('It must be a root dependency.'), 'package-manager-faq-composer-patches-not-a-root-dependency');
        }
        // If the plugin is misconfigured in either the active or stage directories,
        // flag an error.
        if ($plugin_installed_in_active && !$active_configuration_ok || $has_staged_update && $plugin_installed_in_stage && !$stage_configuration_ok) {
            $messages[] = $this->t('The <code>composer-exit-on-patch-failure</code> key is not set to <code>true</code> in the <code>extra</code> section of <code>composer.json</code>.');
        }
        if ($messages) {
            $summary = $this->t("Problems detected related to the Composer plugin <code>@plugin</code>.", [
                '@plugin' => static::PLUGIN_NAME,
            ]);
            $event->addError($messages, $summary);
        }
    }
    
    /**
     * Appends a link to online help to an error message.
     *
     * @param \Drupal\Core\StringTranslation\TranslatableMarkup $message
     *   The error message.
     * @param string $fragment
     *   The fragment of the online help to link to.
     *
     * @return \Drupal\Core\StringTranslation\TranslatableMarkup
     *   The final, translated error message.
     */
    private function createErrorMessage(TranslatableMarkup $message, string $fragment) : TranslatableMarkup {
        if ($this->moduleHandler
            ->moduleExists('help')) {
            $url = Url::fromRoute('help.page', [
                'name' => 'package_manager',
            ])->setOption('fragment', $fragment)
                ->toString();
            return $this->t('@message See <a href=":url">the help page</a> for information on how to resolve the problem.', [
                '@message' => $message,
                ':url' => $url,
            ]);
        }
        return $message;
    }
    
    /**
     * Computes the status of the patcher plugin in a particular directory.
     *
     * @param string $working_dir
     *   The directory in which to run Composer.
     *
     * @return bool[]
     *   An indexed array containing three booleans, in order:
     *   - Whether the patcher plugin is installed.
     *   - Whether the patcher plugin is a root requirement in composer.json (in
     *     either the runtime or dev dependencies).
     *   - Whether the `composer-exit-on-patch-failure` flag is set in the `extra`
     *     section of composer.json.
     */
    private function computePatcherStatus(string $working_dir) : array {
        $list = $this->composerInspector
            ->getInstalledPackagesList($working_dir);
        $installed_version = $list[static::PLUGIN_NAME]?->version;
        $info = $this->composerInspector
            ->getRootPackageInfo($working_dir);
        $is_root_requirement = array_key_exists(static::PLUGIN_NAME, $info['requires'] ?? []) || array_key_exists(static::PLUGIN_NAME, $info['devRequires'] ?? []);
        // The 2.x version of the plugin always exits with an error if a patch can't
        // be applied.
        if ($installed_version && Semver::satisfies($installed_version, '^2')) {
            $exit_on_failure = TRUE;
        }
        else {
            $extra = Json::decode($this->composerInspector
                ->getConfig('extra', $working_dir));
            $exit_on_failure = $extra['composer-exit-on-patch-failure'] ?? FALSE;
        }
        return [
            is_string($installed_version),
            $is_root_requirement,
            $exit_on_failure,
        ];
    }
    
    /**
     * {@inheritdoc}
     */
    public static function getSubscribedEvents() : array {
        return [
            PreCreateEvent::class => 'validate',
            PreApplyEvent::class => 'validate',
            StatusCheckEvent::class => 'validate',
        ];
    }

}