class YamlPecl

class YamlPecl implements SerializationInterface {
    
    /**
     * {@inheritdoc}
     */
    public static function encode($data) {
        static $init;
        if (!isset($init)) {
            ini_set('yaml.output_indent', 2);
            // Do not break lines at 80 characters.
            ini_set('yaml.output_width', -1);
            $init = TRUE;
        }
        return yaml_emit($data, YAML_UTF8_ENCODING, YAML_LN_BREAK);
    }
    
    /**
     * {@inheritdoc}
     */
    public static function decode($raw) {
        static $init;
        if (!isset($init)) {
            // Decode binary, since Symfony YAML parser encodes binary from 3.1
            // onwards.
            ini_set('yaml.decode_binary', 1);
            // We never want to unserialize !php/object.
            ini_set('yaml.decode_php', 0);
            $init = TRUE;
        }
        // yaml_parse() will error with an empty value.
        if (!trim($raw)) {
            return NULL;
        }
        // @todo Use ErrorExceptions when https://drupal.org/node/1247666 is in.
        // yaml_parse() will throw errors instead of raising an exception. Until
        // such time as Drupal supports native PHP ErrorExceptions as the error
        // handler, we need to temporarily set the error handler as ::errorHandler()
        // and then restore it after decoding has occurred. This allows us to turn
        // parsing errors into a throwable exception.
        // @see Drupal\Component\Serialization\Exception\InvalidDataTypeException
        // @see http://php.net/manual/class.errorexception.php
        set_error_handler([
            __CLASS__,
            'errorHandler',
        ]);
        $ndocs = 0;
        $data = yaml_parse($raw, 0, $ndocs, [
            YAML_BOOL_TAG => '\\Drupal\\Component\\Serialization\\YamlPecl::applyBooleanCallbacks',
        ]);
        restore_error_handler();
        return $data;
    }
    
    /**
     * Handles errors for \Drupal\Component\Serialization\YamlPecl::decode().
     *
     * @param int $severity
     *   The severity level of the error.
     * @param string $message
     *   The error message to display.
     *
     * @see \Drupal\Component\Serialization\YamlPecl::decode()
     */
    public static function errorHandler($severity, $message) {
        restore_error_handler();
        throw new InvalidDataTypeException($message, $severity);
    }
    
    /**
     * {@inheritdoc}
     */
    public static function getFileExtension() {
        return 'yml';
    }
    
    /**
     * Applies callbacks after parsing to ignore 1.1 style booleans.
     *
     * @param mixed $value
     *   Value from YAML file.
     * @param string $tag
     *   Tag that triggered the callback.
     * @param int $flags
     *   Scalar entity style flags.
     *
     * @return string|bool
     *   FALSE, false, TRUE and true are returned as booleans, everything else is
     *   returned as a string.
     */
    public static function applyBooleanCallbacks($value, $tag, $flags) {
        // YAML 1.1 spec dictates that 'Y', 'N', 'y' and 'n' are booleans. But, we
        // want the 1.2 behavior, so we only consider 'false', 'FALSE', 'true' and
        // 'TRUE' as booleans.
        if (!in_array(strtolower($value), [
            'false',
            'true',
        ], TRUE)) {
            return $value;
        }
        $map = [
            'false' => FALSE,
            'true' => TRUE,
        ];
        return $map[strtolower($value)];
    }

}