class ComponentGenerator

class ComponentGenerator {
    
    /**
     * Relative path from Drupal root to the component directory.
     *
     * @var string
     */
    protected static $relativeComponentPath = 'core/lib/Drupal/Component';
    
    /**
     * Full path to the component directory.
     *
     * @var string
     */
    protected $componentBaseDir;
    
    /**
     * Data from drupal/drupal's composer.json file.
     *
     * @var \Drupal\Composer\Generator\Util\DrupalCoreComposer
     */
    protected $drupalProjectInfo;
    
    /**
     * Data from drupal/core's composer.json file.
     *
     * @var \Drupal\Composer\Generator\Util\DrupalCoreComposer
     */
    protected $drupalCoreInfo;
    
    /**
     * ComponentGenerator constructor.
     */
    public function __construct() {
        $this->componentBaseDir = dirname(__DIR__, 2) . '/' . static::$relativeComponentPath;
    }
    
    /**
     * Find all the composer.json files for components.
     *
     * @return \Symfony\Component\Finder\Finder
     *   A Finder object with all the composer.json files for components.
     */
    public function getComponentPathsFinder() : Finder {
        $composer_json_finder = new Finder();
        $composer_json_finder->name('composer.json')
            ->in($this->componentBaseDir)
            ->ignoreUnreadableDirs()
            ->depth(1);
        return $composer_json_finder;
    }
    
    /**
     * Reconcile Drupal's components whenever composer.lock is updated.
     *
     * @param \Composer\Script\Event $event
     *   The Composer event.
     * @param string $base_dir
     *   Directory where drupal/drupal repository is located.
     */
    public function generate(Event $event, string $base_dir) : void {
        $io = $event->getIO();
        // General information from drupal/drupal and drupal/core composer.json
        // and composer.lock files.
        $this->drupalProjectInfo = DrupalCoreComposer::createFromPath($base_dir);
        $this->drupalCoreInfo = DrupalCoreComposer::createFromPath($base_dir . '/core');
        $changed = FALSE;
        
        /** @var \Symfony\Component\Finder\SplFileInfo $component_composer_json */
        foreach ($this->getComponentPathsFinder()
            ->getIterator() as $component_composer_json) {
            $changed |= $this->generateComponentPackage($event, $component_composer_json->getRelativePathname());
        }
        // Remind the user not to miss files in a patch.
        if ($changed) {
            $io->write("If you make a patch, ensure that the files above are included.");
        }
    }
    
    /**
     * Generate the component JSON files.
     *
     * @param \Composer\Script\Event $event
     *   The Composer event.
     * @param string $component_pathname
     *   Relative path to the composer.json file for a component.
     *
     * @return bool
     *   TRUE if the generated component package is different from what is on
     *   disk.
     */
    protected function generateComponentPackage(Event $event, string $component_pathname) : bool {
        $io = $event->getIO();
        $composer_json_path = $this->componentBaseDir . '/' . $component_pathname;
        $original_composer_json = file_exists($composer_json_path) ? file_get_contents($composer_json_path) : '';
        // Modify the original data.
        $composer_json_data = $this->getPackage($io, $original_composer_json);
        $updated_composer_json = static::encode($composer_json_data);
        // Exit early if nothing changed.
        if (trim($original_composer_json, " \t\r\x00\v") === trim($updated_composer_json, " \t\r\x00\v")) {
            return FALSE;
        }
        // Warn the user that a component file has been updated.
        $display_path = static::$relativeComponentPath . '/' . $component_pathname;
        $io->write("Updated component file <info>{$display_path}</info>.");
        // Write the composer.json file back to disk.
        $fs = new Filesystem();
        $fs->ensureDirectoryExists(dirname($composer_json_path));
        file_put_contents($composer_json_path, $updated_composer_json);
        return TRUE;
    }
    
    /**
     * Reconcile component dependencies with core.
     *
     * @param \Composer\IO\IOInterface $io
     *   IO object for messages to the user.
     * @param string $original_json
     *   Contents of the component's composer.json file.
     *
     * @return array
     *   Structured data to be turned back into JSON.
     */
    protected function getPackage(IOInterface $io, string $original_json) : array {
        $original_data = json_decode($original_json, TRUE);
        $package_data = array_merge($original_data, $this->initialPackageMetadata());
        $core_info = $this->drupalCoreInfo
            ->rootComposerJson();
        $stability = VersionParser::parseStability(\Drupal::VERSION);
        // List of packages which we didn't find in either core requirement.
        $not_in_core = [];
        // Traverse required packages.
        foreach (array_keys($original_data['require'] ?? []) as $package_name) {
            // Reconcile locked constraints from drupal/drupal. We might have a locked
            // version of a dependency that's not present in drupal/core.
            if ($info = $this->drupalProjectInfo
                ->packageLockInfo($package_name)) {
                $package_data['require'][$package_name] = $info['version'];
            }
            elseif ($package_name !== 'php' && strpos($package_name, 'drupal/core-') === FALSE) {
                $not_in_core[$package_name] = $package_name;
            }
            // Reconcile looser constraints from drupal/core, and we're totally OK
            // with over-writing the locked ones from above.
            if ($constraint = $core_info['require'][$package_name] ?? FALSE) {
                $package_data['require'][$package_name] = $constraint;
            }
            // Reconcile dependencies on other Drupal components, so we can set the
            // constraint to our current version.
            if (strpos($package_name, 'drupal/core-') !== FALSE) {
                if ($stability === 'stable') {
                    // Set the constraint to ^maj.min.
                    $package_data['require'][$package_name] = SemanticVersion::majorMinorConstraint(\Drupal::VERSION);
                }
                else {
                    // For non-stable releases, set the constraint to the branch version.
                    $package_data['require'][$package_name] = Composer::drupalVersionBranch();
                    // Also for non-stable releases which depend on another component,
                    // set the minimum stability. We do this so we can test build the
                    // components. Minimum-stability is otherwise ignored for packages
                    // which aren't the root package, so for any other purpose, this is
                    // unneeded.
                    $package_data['minimum-stability'] = $stability;
                }
            }
        }
        if ($not_in_core) {
            $io->error($package_data['name'] . ' requires packages not present in drupal/drupal: ' . implode(', ', $not_in_core));
        }
        return $package_data;
    }
    
    /**
     * Utility function to encode package json in a consistent way.
     *
     * @param array $composer_json_data
     *   Data to encode into a json string.
     *
     * @return string
     *   Encoded version of provided json data.
     */
    public static function encode(array $composer_json_data) : string {
        return json_encode($composer_json_data, JSON_PRETTY_PRINT | JSON_UNESCAPED_SLASHES) . "\n";
    }
    
    /**
     * Common default metadata for all components.
     *
     * @return array
     *   An array containing the common default metadata for all components.
     */
    protected function initialPackageMetadata() : array {
        return [
            'extra' => [
                '_readme' => [
                    'This file was partially generated automatically. See: https://www.drupal.org/node/3293830',
                ],
            ],
            // Always reconcile PHP version.
'require' => [
                'php' => '>=7.3.0',
            ],
        ];
    }

}