class Updater

abstract class Updater {
    
    /**
     * Directory to install from.
     *
     * @var string
     */
    public $source;
    
    /**
     * The root directory under which new projects will be copied.
     *
     * @var string
     */
    protected $root;
    
    /**
     * The name of the project directory (basename).
     */
    protected string $name;
    
    /**
     * The title of the project.
     */
    protected string $title;
    
    /**
     * Constructs a new updater.
     *
     * @param string $source
     *   Directory to install from.
     * @param string $root
     *   The root directory under which the project will be copied to if it's a
     *   new project. Usually this is the app root (the directory in which the
     *   Drupal site is installed).
     */
    public function __construct($source, $root) {
        $this->source = $source;
        $this->root = $root;
        $this->name = self::getProjectName($source);
        $this->title = self::getProjectTitle($source);
    }
    
    /**
     * Returns an Updater of the appropriate type depending on the source.
     *
     * If a directory is provided which contains a module, will return a
     * ModuleUpdater.
     *
     * @param string $source
     *   Directory of a Drupal project.
     * @param string $root
     *   The root directory under which the project will be copied to if it's a
     *   new project. Usually this is the app root (the directory in which the
     *   Drupal site is installed).
     *
     * @return \Drupal\Core\Updater\Updater
     *   A new Drupal\Core\Updater\Updater object.
     *
     * @throws \Drupal\Core\Updater\UpdaterException
     */
    public static function factory($source, $root) {
        if (is_dir($source)) {
            $updater = self::getUpdaterFromDirectory($source);
        }
        else {
            throw new UpdaterException('Unable to determine the type of the source directory.');
        }
        return new $updater($source, $root);
    }
    
    /**
     * Determines which Updater class can operate on the given directory.
     *
     * @param string $directory
     *   Extracted Drupal project.
     *
     * @return string
     *   The class name which can work with this project type.
     *
     * @throws \Drupal\Core\Updater\UpdaterException
     */
    public static function getUpdaterFromDirectory($directory) {
        // Gets a list of possible implementing classes.
        $updaters = drupal_get_updaters();
        foreach ($updaters as $updater) {
            $class = $updater['class'];
            if (call_user_func([
                $class,
                'canUpdateDirectory',
            ], $directory)) {
                return $class;
            }
        }
        throw new UpdaterException('Cannot determine the type of project.');
    }
    
    /**
     * Determines what the most important (or only) info file is in a directory.
     *
     * Since there is no enforcement of which info file is the project's "main"
     * info file, this will get one with the same name as the directory, or the
     * first one it finds.  Not ideal, but needs a larger solution.
     *
     * @param string $directory
     *   Directory to search in.
     *
     * @return string
     *   Path to the info file.
     */
    public static function findInfoFile($directory) {
        
        /** @var \Drupal\Core\File\FileSystemInterface $file_system */
        $file_system = \Drupal::service('file_system');
        $info_files = [];
        if (is_dir($directory)) {
            $info_files = $file_system->scanDirectory($directory, '/.*\\.info.yml$/');
        }
        if (!$info_files) {
            return FALSE;
        }
        foreach ($info_files as $info_file) {
            if (mb_substr($info_file->filename, 0, -9) == $file_system->basename($directory)) {
                // Info file Has the same name as the directory, return it.
                return $info_file->uri;
            }
        }
        // Otherwise, return the first one.
        $info_file = array_shift($info_files);
        return $info_file->uri;
    }
    
    /**
     * Get Extension information from directory.
     *
     * @param string $directory
     *   Directory to search in.
     *
     * @return array
     *   Extension info.
     *
     * @throws \Drupal\Core\Updater\UpdaterException
     *   If the info parser does not provide any info.
     */
    protected static function getExtensionInfo($directory) {
        $info_file = static::findInfoFile($directory);
        $info = \Drupal::service('info_parser')->parse($info_file);
        if (empty($info)) {
            throw new UpdaterException("Unable to parse info file: '{$info_file}'.");
        }
        return $info;
    }
    
    /**
     * Gets the name of the project directory (basename).
     *
     * @todo It would be nice, if projects contained an info file which could
     *   provide their canonical name.
     *
     * @param string $directory
     *   The full directory path.
     *
     * @return string
     *   The name of the project.
     */
    public static function getProjectName($directory) {
        return \Drupal::service('file_system')->basename($directory);
    }
    
    /**
     * Returns the project name from a Drupal info file.
     *
     * @param string $directory
     *   Directory to search for the info file.
     *
     * @return string
     *   The title of the project.
     *
     * @throws \Drupal\Core\Updater\UpdaterException
     */
    public static function getProjectTitle($directory) {
        $info_file = self::findInfoFile($directory);
        $info = \Drupal::service('info_parser')->parse($info_file);
        if (empty($info)) {
            throw new UpdaterException("Unable to parse info file: '{$info_file}'.");
        }
        return $info['name'];
    }
    
    /**
     * Returns the path to the default install location for the current project.
     *
     * @return string
     *   The absolute path of the directory.
     */
    public abstract function getInstallDirectory();
    
    /**
     * Stores the default parameters for the Updater.
     *
     * @param array $overrides
     *   An array of overrides for the default parameters.
     *
     * @return array
     *   An array of configuration parameters for an update or install operation.
     */
    protected function getInstallArgs($overrides = []) {
        $args = [
            'make_backup' => FALSE,
            'install_dir' => $this->getInstallDirectory(),
            'backup_dir' => $this->getBackupDir(),
        ];
        return array_merge($args, $overrides);
    }
    
    /**
     * Updates a Drupal project and returns a list of next actions.
     *
     * @param \Drupal\Core\FileTransfer\FileTransfer $filetransfer
     *   Object that is a child of FileTransfer. Used for moving files
     *   to the server.
     * @param array $overrides
     *   An array of settings to override defaults; see self::getInstallArgs().
     *
     * @return array
     *   An array of links which the user may need to complete the update
     *
     * @throws \Drupal\Core\Updater\UpdaterException
     * @throws \Drupal\Core\Updater\UpdaterFileTransferException
     */
    public function update(&$filetransfer, $overrides = []) {
        try {
            // Establish arguments with possible overrides.
            $args = $this->getInstallArgs($overrides);
            // Take a Backup.
            if ($args['make_backup']) {
                $this->makeBackup($filetransfer, $args['install_dir'], $args['backup_dir']);
            }
            if (!$this->name) {
                // This is bad, don't want to delete the install directory.
                throw new UpdaterException('Fatal error in update, cowardly refusing to wipe out the install directory.');
            }
            // Make sure the installation parent directory exists and is writable.
            $this->prepareInstallDirectory($filetransfer, $args['install_dir']);
            if (is_dir($args['install_dir'] . '/' . $this->name)) {
                // Remove the existing installed file.
                $filetransfer->removeDirectory($args['install_dir'] . '/' . $this->name);
            }
            // Copy the directory in place.
            $filetransfer->copyDirectory($this->source, $args['install_dir']);
            // Make sure what we just installed is readable by the web server.
            $this->makeWorldReadable($filetransfer, $args['install_dir'] . '/' . $this->name);
            // Run the updates.
            // @todo Decide if we want to implement this.
            $this->postUpdate();
            // For now, just return a list of links of things to do.
            return $this->postUpdateTasks();
        } catch (FileTransferException $e) {
            throw new UpdaterFileTransferException("File Transfer failed, reason: '" . strtr($e->getMessage(), $e->arguments) . "'");
        }
    }
    
    /**
     * Installs a Drupal project, returns a list of next actions.
     *
     * @param \Drupal\Core\FileTransfer\FileTransfer $filetransfer
     *   Object that is a child of FileTransfer.
     * @param array $overrides
     *   An array of settings to override defaults; see self::getInstallArgs().
     *
     * @return array
     *   An array of links which the user may need to complete the install.
     *
     * @throws \Drupal\Core\Updater\UpdaterFileTransferException
     */
    public function install(&$filetransfer, $overrides = []) {
        try {
            // Establish arguments with possible overrides.
            $args = $this->getInstallArgs($overrides);
            // Make sure the installation parent directory exists and is writable.
            $this->prepareInstallDirectory($filetransfer, $args['install_dir']);
            // Copy the directory in place.
            $filetransfer->copyDirectory($this->source, $args['install_dir']);
            // Make sure what we just installed is readable by the web server.
            $this->makeWorldReadable($filetransfer, $args['install_dir'] . '/' . $this->name);
            // Potentially enable something?
            // @todo Decide if we want to implement this.
            $this->postInstall();
            // For now, just return a list of links of things to do.
            return $this->postInstallTasks();
        } catch (FileTransferException $e) {
            throw new UpdaterFileTransferException("File Transfer failed, reason: '" . strtr($e->getMessage(), $e->arguments) . "'");
        }
    }
    
    /**
     * Makes sure the installation parent directory exists and is writable.
     *
     * @param \Drupal\Core\FileTransfer\FileTransfer $filetransfer
     *   Object which is a child of FileTransfer.
     * @param string $directory
     *   The installation directory to prepare.
     *
     * @throws \Drupal\Core\Updater\UpdaterException
     */
    public function prepareInstallDirectory(&$filetransfer, $directory) {
        // Make the parent dir writable if need be and create the dir.
        if (!is_dir($directory)) {
            $parent_dir = dirname($directory);
            if (!is_writable($parent_dir)) {
                @chmod($parent_dir, 0755);
                // It is expected that this will fail if the directory is owned by the
                // FTP user. If the FTP user == web server, it will succeed.
                try {
                    $filetransfer->createDirectory($directory);
                    $this->makeWorldReadable($filetransfer, $directory);
                } catch (FileTransferException $e) {
                    // Probably still not writable. Try to chmod and do it again.
                    // @todo Make a new exception class so we can catch it differently.
                    try {
                        $old_perms = fileperms($parent_dir) & 0777;
                        $filetransfer->chmod($parent_dir, 0755);
                        $filetransfer->createDirectory($directory);
                        $this->makeWorldReadable($filetransfer, $directory);
                        // Put the permissions back.
                        $filetransfer->chmod($parent_dir, $old_perms);
                    } catch (FileTransferException $e) {
                        $message = t($e->getMessage(), $e->arguments);
                        $throw_message = t('Unable to create %directory due to the following: %reason', [
                            '%directory' => $directory,
                            '%reason' => $message,
                        ]);
                        throw new UpdaterException($throw_message);
                    }
                }
                // Put the parent directory back.
                @chmod($parent_dir, 0555);
            }
        }
    }
    
    /**
     * Ensures that a given directory is world readable.
     *
     * @param \Drupal\Core\FileTransfer\FileTransfer $filetransfer
     *   Object which is a child of FileTransfer.
     * @param string $path
     *   The file path to make world readable.
     * @param bool $recursive
     *   If the chmod should be applied recursively.
     */
    public function makeWorldReadable(&$filetransfer, $path, $recursive = TRUE) {
        if (!is_executable($path)) {
            // Set it to read + execute.
            $new_perms = fileperms($path) & 0777 | 05;
            $filetransfer->chmod($path, $new_perms, $recursive);
        }
    }
    
    /**
     * Performs a backup.
     *
     * @param \Drupal\Core\FileTransfer\FileTransfer $filetransfer
     *   Object which is a child of FileTransfer.
     * @param string $from
     *   The file path to copy from.
     * @param string $to
     *   The file path to copy to.
     *
     * @todo Not implemented: https://www.drupal.org/node/2474355
     */
    public function makeBackup(FileTransfer $filetransfer, $from, $to) {
    }
    
    /**
     * Returns the full path to a directory where backups should be written.
     */
    public function getBackupDir() {
        return \Drupal::service('stream_wrapper_manager')->getViaScheme('temporary')
            ->getDirectoryPath();
    }
    
    /**
     * Performs actions after new code is updated.
     */
    public function postUpdate() {
    }
    
    /**
     * Performs actions after installation.
     */
    public function postInstall() {
    }
    
    /**
     * Returns an array of links to pages that should be visited post operation.
     *
     * @return array
     *   Links which provide actions to take after the install is finished.
     */
    public function postInstallTasks() {
        return [];
    }
    
    /**
     * Returns an array of links to pages that should be visited post operation.
     *
     * @return array
     *   Links which provide actions to take after the update is finished.
     */
    public function postUpdateTasks() {
        return [];
    }

}