class YamlDirectoryDiscovery

class YamlDirectoryDiscovery implements DiscoverableInterface {
    
    /**
     * Defines the key in the discovered data where the file path is stored.
     */
    const FILE_KEY = '_discovered_file_path';
    
    /**
     * An array of directories to scan, keyed by the provider.
     *
     * The value can either be a string or an array of strings. The string values
     * should be the path of a directory to scan.
     *
     * @var array
     */
    protected $directories = [];
    
    /**
     * The suffix for the file cache key.
     *
     * @var string
     */
    protected $fileCacheKeySuffix;
    
    /**
     * The key contained in the discovered data that identifies it.
     *
     * @var string
     */
    protected $idKey;
    
    /**
     * Constructs a YamlDirectoryDiscovery object.
     *
     * @param array $directories
     *   An array of directories to scan, keyed by the provider. The value can
     *   either be a string or an array of strings. The string values should be
     *   the path of a directory to scan.
     * @param string $file_cache_key_suffix
     *   The file cache key suffix. This should be unique for each type of
     *   discovery.
     * @param string $key
     *   (optional) The key contained in the discovered data that identifies it.
     *   Defaults to 'id'.
     */
    public function __construct(array $directories, $file_cache_key_suffix, $key = 'id') {
        $this->directories = $directories;
        $this->fileCacheKeySuffix = $file_cache_key_suffix;
        $this->idKey = $key;
    }
    
    /**
     * {@inheritdoc}
     */
    public function findAll() {
        $all = [];
        $files = $this->findFiles();
        $file_cache = FileCacheFactory::get('yaml_discovery:' . $this->fileCacheKeySuffix);
        // Try to load from the file cache first.
        foreach ($file_cache->getMultiple(array_keys($files)) as $file => $data) {
            $all[$files[$file]][$this->getIdentifier($file, $data)] = $data;
            unset($files[$file]);
        }
        // If there are files left that were not returned from the cache, load and
        // parse them now. This list was flipped above and is keyed by filename.
        if ($files) {
            foreach ($files as $file => $provider) {
                // If a file is empty or its contents are commented out, return an empty
                // array instead of NULL for type consistency.
                try {
                    $data = Yaml::decode(file_get_contents($file)) ?: [];
                } catch (InvalidDataTypeException $e) {
                    throw new DiscoveryException("The {$file} contains invalid YAML", 0, $e);
                }
                $data[static::FILE_KEY] = $file;
                $all[$provider][$this->getIdentifier($file, $data)] = $data;
                $file_cache->set($file, $data);
            }
        }
        return $all;
    }
    
    /**
     * Gets the identifier from the data.
     *
     * @param string $file
     *   The filename.
     * @param array $data
     *   The data from the YAML file.
     *
     * @return string
     *   The identifier from the data.
     */
    protected function getIdentifier($file, array $data) {
        if (!isset($data[$this->idKey])) {
            throw new DiscoveryException("The {$file} contains no data in the identifier key '{$this->idKey}'");
        }
        return $data[$this->idKey];
    }
    
    /**
     * Returns an array of providers keyed by file path.
     *
     * @return array
     *   An array of providers keyed by file path.
     */
    protected function findFiles() {
        $file_list = [];
        foreach ($this->directories as $provider => $directories) {
            $directories = (array) $directories;
            foreach ($directories as $directory) {
                if (is_dir($directory)) {
                    
                    /** @var \SplFileInfo $fileInfo */
                    foreach ($this->getDirectoryIterator($directory) as $fileInfo) {
                        $file_list[$fileInfo->getPathname()] = $provider;
                    }
                }
            }
        }
        return $file_list;
    }
    
    /**
     * Gets an iterator to loop over the files in the provided directory.
     *
     * This method exists so that it is easy to replace this functionality in a
     * class that extends this one. For example, it could be used to make the scan
     * recursive.
     *
     * @param string $directory
     *   The directory to scan.
     *
     * @return \Traversable
     *   An \Traversable object or array where the values are \SplFileInfo
     *   objects.
     */
    protected function getDirectoryIterator($directory) {
        return new RegexDirectoryIterator($directory, '/\\.yml$/i');
    }

}