class YamlDiscovery

class YamlDiscovery implements DiscoverableInterface {
    
    /**
     * The base filename to look for in each directory.
     *
     * @var string
     */
    protected $name;
    
    /**
     * An array of directories to scan, keyed by the provider.
     *
     * @var array
     */
    protected $directories = [];
    
    /**
     * Constructs a YamlDiscovery object.
     *
     * @param string $name
     *   The base filename to look for in each directory. The format will be
     *   $provider.$name.yml.
     * @param array $directories
     *   An array of directories to scan, keyed by the provider.
     */
    public function __construct($name, array $directories) {
        $this->name = $name;
        $this->directories = $directories;
    }
    
    /**
     * {@inheritdoc}
     */
    public function findAll() {
        $all = [];
        $files = $this->findFiles();
        $provider_by_files = array_flip($files);
        $file_cache = FileCacheFactory::get('yaml_discovery:' . $this->name);
        // Try to load from the file cache first.
        foreach ($file_cache->getMultiple($files) as $file => $data) {
            $all[$provider_by_files[$file]] = $data;
            unset($provider_by_files[$file]);
        }
        // If there are files left that were not returned from the cache, load and
        // parse them now. This list was flipped above and is keyed by filename.
        if ($provider_by_files) {
            foreach ($provider_by_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.
                $all[$provider] = $this->decode($file);
                $file_cache->set($file, $all[$provider]);
            }
        }
        return $all;
    }
    
    /**
     * Decode a YAML file.
     *
     * @param string $file
     *   Yaml file path.
     *
     * @return array
     */
    protected function decode($file) {
        try {
            return Yaml::decode(file_get_contents($file)) ?: [];
        } catch (InvalidDataTypeException $e) {
            throw new InvalidDataTypeException($file . ': ' . $e->getMessage(), $e->getCode(), $e);
        }
    }
    
    /**
     * Returns an array of file paths, keyed by provider.
     *
     * @return array
     */
    protected function findFiles() {
        $files = [];
        foreach ($this->directories as $provider => $directory) {
            $file = $directory . '/' . $provider . '.' . $this->name . '.yml';
            if (file_exists($file)) {
                $files[$provider] = $file;
            }
        }
        return $files;
    }

}