class ExtensionDiscovery

class ExtensionDiscovery {

  /**
   * Origin directory weight: Core.
   */
  const ORIGIN_CORE = 0;

  /**
   * Origin directory weight: Installation profile.
   */
  const ORIGIN_PROFILE = 1;

  /**
   * Origin directory weight: sites/all.
   */
  const ORIGIN_SITES_ALL = 2;

  /**
   * Origin directory weight: Site-wide directory.
   */
  const ORIGIN_ROOT = 3;

  /**
   * Origin directory weight: Parent site directory of a test site environment.
   */
  const ORIGIN_PARENT_SITE = 4;

  /**
   * Origin directory weight: Site-specific directory.
   */
  const ORIGIN_SITE = 5;

  /**
   * Regular expression to match PHP function names.
   *
   * @see http://php.net/manual/functions.user-defined.php
   */
  const PHP_FUNCTION_PATTERN = '/^[a-zA-Z_\\x7f-\\xff][a-zA-Z0-9_\\x7f-\\xff]*$/';

  /**
   * Previously discovered files keyed by origin directory and extension type.
   *
   * @var array
   */
  protected static $files = [];

  /**
   * List of installation profile directories to additionally scan.
   *
   * @var array
   */
  protected $profileDirectories;

  /**
   * The app root for the current operation.
   *
   * @var string
   */
  protected $root;

  /**
   * The file cache object.
   *
   * @var \Drupal\Component\FileCache\FileCacheInterface
   */
  protected $fileCache;

  /**
   * The site path.
   *
   * @var string
   */
  protected $sitePath;

  /**
   * Constructs a new ExtensionDiscovery object.
   *
   * @param string $root
   *   The app root.
   * @param bool $use_file_cache
   *   Whether file cache should be used.
   * @param string[] $profile_directories
   *   The available profile directories
   * @param string $site_path
   *   The path to the site.
   */
  public function __construct(string $root, $use_file_cache = TRUE, array $profile_directories = NULL, string $site_path = NULL) {
    $this->root = $root;
    $this->fileCache = $use_file_cache ? FileCacheFactory::get('extension_discovery') : NULL;
    $this->profileDirectories = $profile_directories;
    $this->sitePath = $site_path;
  }

  /**
   * Discovers available extensions of a given type.
   *
   * Finds all extensions (modules, themes, etc) that exist on the site. It
   * searches in several locations. For instance, to discover all available
   * modules:
   * @code
   * $listing = new ExtensionDiscovery(\Drupal::root());
   * $modules = $listing->scan('module');
   * @endcode
   *
   * The following directories will be searched (in the order stated):
   * - the core directory; i.e., /core
   * - the installation profile directory; e.g., /core/profiles/standard
   * - the legacy site-wide directory; i.e., /sites/all
   * - the site-wide directory; i.e., /
   * - the site-specific directory; e.g., /sites/example.com
   *
   * To also find test modules, add
   * @code
   * $settings['extension_discovery_scan_tests'] = TRUE;
   * @endcode
   * to your settings.php.
   *
   * The information is returned in an associative array, keyed by the extension
   * name (without .info.yml extension). Extensions found later in the search
   * will take precedence over extensions found earlier - unless they are not
   * compatible with the current version of Drupal core.
   *
   * @param string $type
   *   The extension type to search for. One of 'profile', 'module', 'theme', or
   *   'theme_engine'.
   * @param bool $include_tests
   *   (optional) Whether to explicitly include or exclude test extensions. By
   *   default, test extensions are only discovered when in a test environment.
   *
   * @return \Drupal\Core\Extension\Extension[]
   *   An associative array of Extension objects, keyed by extension name.
   */
  public function scan($type, $include_tests = NULL) {

    // Determine the installation profile directories to scan for extensions,
    // unless explicit profile directories have been set. Exclude profiles as we
    // cannot have profiles within profiles.
    if (!isset($this->profileDirectories) && $type != 'profile') {
      $this
        ->setProfileDirectoriesFromSettings();
    }

    // Search the core directory.
    $search_dirs[static::ORIGIN_CORE] = 'core';

    // Search the legacy sites/all directory.
    $search_dirs[static::ORIGIN_SITES_ALL] = 'sites/all';

    // Search for contributed and custom extensions in top-level directories.
    // The scan uses a list of extension types to limit recursion to the
    // expected extension type specific directory names only.
    $search_dirs[static::ORIGIN_ROOT] = '';

    // Tests use the regular built-in multi-site functionality of Drupal for
    // running web tests. As a consequence, extensions of the parent site
    // located in a different site-specific directory are not discovered in a
    // test site environment, because the site directories are not the same.
    // Therefore, add the site directory of the parent site to the search paths,
    // so that contained extensions are still discovered.
    // @see \Drupal\Core\Test\FunctionalTestSetupTrait::prepareSettings().
    if ($parent_site = Settings::get('test_parent_site')) {
      $search_dirs[static::ORIGIN_PARENT_SITE] = $parent_site;
    }

    // Find the site-specific directory to search. Since we are using this
    // method to discover extensions including profiles, we might be doing this
    // at install time. Therefore Kernel service is not always available, but is
    // preferred.
    if (\Drupal::hasService('kernel')) {
      $search_dirs[static::ORIGIN_SITE] = \Drupal::getContainer()
        ->getParameter('site.path');
    }
    else {
      $search_dirs[static::ORIGIN_SITE] = $this->sitePath ?: DrupalKernel::findSitePath(Request::createFromGlobals());
    }

    // Unless an explicit value has been passed, manually check whether we are
    // in a test environment, in which case test extensions must be included.
    // Test extensions can also be included for debugging purposes by setting a
    // variable in settings.php.
    if (!isset($include_tests)) {
      $include_tests = Settings::get('extension_discovery_scan_tests') || drupal_valid_test_ua();
    }
    $files = [];
    foreach ($search_dirs as $dir) {

      // Discover all extensions in the directory, unless we did already.
      if (!isset(static::$files[$this->root][$dir][$include_tests])) {
        static::$files[$this->root][$dir][$include_tests] = $this
          ->scanDirectory($dir, $include_tests);
      }

      // Only return extensions of the requested type.
      if (isset(static::$files[$this->root][$dir][$include_tests][$type])) {
        $files += static::$files[$this->root][$dir][$include_tests][$type];
      }
    }

    // If applicable, filter out extensions that do not belong to the current
    // installation profiles.
    $files = $this
      ->filterByProfileDirectories($files);

    // Sort the discovered extensions by their originating directories.
    $origin_weights = array_flip($search_dirs);
    $files = $this
      ->sort($files, $origin_weights);

    // Process and return the list of extensions keyed by extension name.
    return $this
      ->process($files);
  }

  /**
   * Sets installation profile directories based on current site settings.
   *
   * @return $this
   */
  public function setProfileDirectoriesFromSettings() {
    $this->profileDirectories = [];

    // This method may be called by the database system early in bootstrap
    // before the container is initialized. In that case, the parameter is not
    // accessible yet, hence return.
    if (!\Drupal::hasContainer() || !\Drupal::getContainer()
      ->hasParameter('install_profile')) {
      return $this;
    }
    $profile = \Drupal::installProfile();

    // If $profile is FALSE then we need to add a fake directory as a profile
    // directory in order to filter out profile provided modules. This ensures
    // that, after uninstalling a profile, a site cannot install modules
    // contained in an install profile. During installation $profile will be
    // NULL, so we need to discover all modules and profiles.
    if ($profile === FALSE) {

      // cspell:ignore CNKDSIUSYFUISEFCB
      $this->profileDirectories[] = '_does_not_exist_profile_CNKDSIUSYFUISEFCB';
    }
    elseif ($profile) {
      $this->profileDirectories[] = \Drupal::service('extension.list.profile')
        ->getPath($profile);
    }
    return $this;
  }

  /**
   * Gets the installation profile directories to be scanned.
   *
   * @return array
   *   A list of installation profile directory paths relative to the system
   *   root directory.
   */
  public function getProfileDirectories() {
    return $this->profileDirectories;
  }

  /**
   * Sets explicit profile directories to scan.
   *
   * @param array $paths
   *   A list of installation profile directory paths relative to the system
   *   root directory (without trailing slash) to search for extensions.
   *
   * @return $this
   */
  public function setProfileDirectories(array $paths = NULL) {
    $this->profileDirectories = $paths;
    return $this;
  }

  /**
   * Filters out extensions not belonging to the scanned installation profiles.
   *
   * @param \Drupal\Core\Extension\Extension[] $all_files
   *   The list of all extensions.
   *
   * @return \Drupal\Core\Extension\Extension[]
   *   The filtered list of extensions.
   */
  protected function filterByProfileDirectories(array $all_files) {
    if (empty($this->profileDirectories)) {
      return $all_files;
    }
    $all_files = array_filter($all_files, function ($file) {
      if (!str_starts_with($file->subpath, 'profiles')) {

        // This extension doesn't belong to a profile, ignore it.
        return TRUE;
      }
      foreach ($this->profileDirectories as $profile_path) {
        if (str_starts_with($file
          ->getPath(), $profile_path)) {

          // Parent profile found.
          return TRUE;
        }
      }
      return FALSE;
    });
    return $all_files;
  }

  /**
   * Sorts the discovered extensions.
   *
   * @param \Drupal\Core\Extension\Extension[] $all_files
   *   The list of all extensions.
   * @param array $weights
   *   An array of weights, keyed by originating directory.
   *
   * @return \Drupal\Core\Extension\Extension[]
   *   The sorted list of extensions.
   */
  protected function sort(array $all_files, array $weights) {
    $origins = [];
    $profiles = [];
    foreach ($all_files as $key => $file) {

      // If the extension does not belong to a profile, just apply the weight
      // of the originating directory.
      if (!str_starts_with($file->subpath, 'profiles')) {
        $origins[$key] = $weights[$file->origin];
        $profiles[$key] = NULL;
      }
      elseif (empty($this->profileDirectories)) {
        $origins[$key] = static::ORIGIN_PROFILE;
        $profiles[$key] = NULL;
      }
      else {

        // Apply the weight of the originating profile directory.
        foreach ($this->profileDirectories as $weight => $profile_path) {
          if (str_starts_with($file
            ->getPath(), $profile_path)) {
            $origins[$key] = static::ORIGIN_PROFILE;
            $profiles[$key] = $weight;
            continue 2;
          }
        }
      }
    }

    // Now sort the extensions by origin and installation profile(s).
    // The result of this multisort can be depicted like the following matrix,
    // whereas the first integer is the weight of the originating directory and
    // the second is the weight of the originating installation profile:
    // 0   core/modules/node/node.module
    // 1 0 profiles/parent_profile/modules/parent_module/parent_module.module
    // 1 1 core/profiles/testing/modules/compatible_test/compatible_test.module
    // 2   sites/all/modules/common/common.module
    // 3   modules/devel/devel.module
    // 4   sites/default/modules/custom/custom.module
    array_multisort($origins, SORT_ASC, $profiles, SORT_ASC, $all_files);
    return $all_files;
  }

  /**
   * Processes the filtered and sorted list of extensions.
   *
   * Extensions discovered in later search paths override earlier, unless they
   * are not compatible with the current version of Drupal core.
   *
   * @param \Drupal\Core\Extension\Extension[] $all_files
   *   The sorted list of all extensions that were found.
   *
   * @return \Drupal\Core\Extension\Extension[]
   *   The filtered list of extensions, keyed by extension name.
   */
  protected function process(array $all_files) {
    $files = [];

    // Duplicate files found in later search directories take precedence over
    // earlier ones; they replace the extension in the existing $files array.
    foreach ($all_files as $file) {
      $files[$file
        ->getName()] = $file;
    }
    return $files;
  }

  /**
   * Recursively scans a base directory for the extensions it contains.
   *
   * @param string $dir
   *   A relative base directory path to scan, without trailing slash.
   * @param bool $include_tests
   *   Whether to include test extensions. If FALSE, all 'tests' directories are
   *   excluded in the search.
   *
   * @return array
   *   An associative array whose keys are extension type names and whose values
   *   are associative arrays of \Drupal\Core\Extension\Extension objects, keyed
   *   by absolute path name.
   *
   * @see \Drupal\Core\Extension\Discovery\RecursiveExtensionFilterCallback
   */
  protected function scanDirectory($dir, $include_tests) {
    $files = [];

    // In order to scan top-level directories, absolute directory paths have to
    // be used (which also improves performance, since any configured PHP
    // include_paths will not be consulted). Retain the relative originating
    // directory being scanned, so relative paths can be reconstructed below
    // (all paths are expected to be relative to $this->root).
    $dir_prefix = $dir == '' ? '' : "{$dir}/";
    $absolute_dir = $dir == '' ? $this->root : $this->root . "/{$dir}";
    if (!is_dir($absolute_dir)) {
      return $files;
    }

    // Use Unix paths regardless of platform, skip dot directories, follow
    // symlinks (to allow extensions to be linked from elsewhere), and return
    // the RecursiveDirectoryIterator instance to have access to getSubPath(),
    // since SplFileInfo does not support relative paths.
    $flags = \FilesystemIterator::UNIX_PATHS;
    $flags |= \FilesystemIterator::SKIP_DOTS;
    $flags |= \FilesystemIterator::FOLLOW_SYMLINKS;
    $flags |= \FilesystemIterator::CURRENT_AS_SELF;
    $directory_iterator = new \RecursiveDirectoryIterator($absolute_dir, $flags);

    // Allow directories specified in settings.php to be ignored. You can use
    // this to not check for files in common special-purpose directories. For
    // example, node_modules and bower_components. Ignoring irrelevant
    // directories is a performance boost.
    $ignore_directories = Settings::get('file_scan_ignore_directories', []);

    // Filter the recursive scan to discover extensions only.
    // Important: Without a RecursiveFilterIterator, RecursiveDirectoryIterator
    // would recurse into the entire filesystem directory tree without any kind
    // of limitations.
    $callback = new RecursiveExtensionFilterCallback($ignore_directories, $include_tests);
    $filter = new \RecursiveCallbackFilterIterator($directory_iterator, [
      $callback,
      'accept',
    ]);

    // The actual recursive filesystem scan is only invoked by instantiating the
    // RecursiveIteratorIterator.
    $iterator = new \RecursiveIteratorIterator($filter, \RecursiveIteratorIterator::LEAVES_ONLY, \RecursiveIteratorIterator::CATCH_GET_CHILD);
    foreach ($iterator as $key => $fileinfo) {

      // All extension names in Drupal have to be valid PHP function names due
      // to the module hook architecture.
      if (!preg_match(static::PHP_FUNCTION_PATTERN, $fileinfo
        ->getBasename('.info.yml'))) {
        continue;
      }
      $extension_arguments = $this->fileCache ? $this->fileCache
        ->get($fileinfo
        ->getPathName()) : FALSE;

      // Ensure $extension_arguments is an array. Previously, the Extension
      // object was cached and now needs to be replaced with the array.
      if (empty($extension_arguments) || !is_array($extension_arguments)) {

        // Determine extension type from info file.
        $type = FALSE;
        $file = $fileinfo
          ->openFile('r');
        while (!$type && !$file
          ->eof()) {
          preg_match('@^type:\\s*(\'|")?(\\w+)\\1?\\s*(?:\\#.*)?$@', $file
            ->fgets(), $matches);
          if (isset($matches[2])) {
            $type = $matches[2];
          }
        }
        if (empty($type)) {
          continue;
        }
        $name = $fileinfo
          ->getBasename('.info.yml');
        $pathname = $dir_prefix . $fileinfo
          ->getSubPathname();

        // Determine whether the extension has a main extension file.
        // For theme engines, the file extension is .engine.
        if ($type == 'theme_engine') {
          $filename = $name . '.engine';
        }
        else {
          $filename = $name . '.' . $type;
        }
        if (!file_exists($this->root . '/' . dirname($pathname) . '/' . $filename)) {
          $filename = NULL;
        }
        $extension_arguments = [
          'type' => $type,
          'pathname' => $pathname,
          'filename' => $filename,
          'subpath' => $fileinfo
            ->getSubPath(),
        ];
        if ($this->fileCache) {
          $this->fileCache
            ->set($fileinfo
            ->getPathName(), $extension_arguments);
        }
      }
      $extension = new Extension($this->root, $extension_arguments['type'], $extension_arguments['pathname'], $extension_arguments['filename']);

      // Track the originating directory for sorting purposes.
      $extension->subpath = $extension_arguments['subpath'];
      $extension->origin = $dir;
      $files[$extension_arguments['type']][$key] = $extension;
    }
    return $files;
  }

}