class SimpleExifToolFacade

class SimpleExifToolFacade implements ExifInterface {
    private static $instance = NULL;
    
    /**
     * We are implementing a singleton pattern.
     */
    private function __construct() {
    }
    
    /**
     * Return singleton instance.
     *
     * @return \Drupal\exif\ExifInterface
     *   the chosen implementation instance.
     */
    public static function getInstance() {
        if (is_null(self::$instance)) {
            self::$instance = new self();
        }
        return self::$instance;
    }
    
    /**
     * Check the exiftool is available.
     *
     * @return bool
     *   TRUE if available.
     */
    public static function checkConfiguration() {
        $exiftoolLocation = self::getExecutable();
        return isset($exiftoolLocation) && is_executable($exiftoolLocation);
    }
    
    /**
     * Return the 'exiftool' location stored in exif settings.
     *
     * @return string
     *   path to 'exiftool'.
     */
    private static function getExecutable() {
        $config = Drupal::configFactory()->get('exif.settings');
        return $config->get('exiftool_location');
    }
    
    /**
     * {@inheritdoc}
     */
    public function getMetadataFields(array $arCckFields = []) {
        foreach ($arCckFields as $drupal_field => $metadata_settings) {
            $metadata_field = $metadata_settings['metadata_field'];
            $ar = explode("_", $metadata_field);
            if (isset($ar[0])) {
                $section = $ar[0];
                unset($ar[0]);
                $arCckFields[$drupal_field]['metadata_field'] = [
                    'section' => $section,
                    'tag' => implode("_", $ar),
                ];
            }
        }
        return $arCckFields;
    }
    
    /**
     * {@inheritdoc}
     */
    public function readMetadataTags($file, $enable_sections = TRUE) {
        if (!file_exists($file)) {
            return [];
        }
        $data = $this->readAllInformation($file, $enable_sections);
        return $data;
    }
    
    /**
     * Retrieve all metadata using exifTool.
     *
     * @param string $file
     *   Image to scan.
     * @param bool $enable_sections
     *   Extract sections or not.
     * @param bool $enable_markerNote
     *   Extract marker notes or not (for now, always FALSE)
     * @param bool $enable_non_supported_tags
     *   Extract non supported tags or not (for now, always FALSE)
     *
     * @return array
     *   all metadata usable by this module.
     */
    private function readAllInformation($file, $enable_sections = TRUE, $enable_markerNote = FALSE, $enable_non_supported_tags = FALSE) {
        $jsonAsString = $this->runTool($file, $enable_sections, $enable_markerNote, $enable_non_supported_tags);
        $json = json_decode($jsonAsString, TRUE);
        $errorCode = json_last_error();
        if ($errorCode == JSON_ERROR_NONE) {
            return $this->toLowerJsonResult($json[0]);
        }
        else {
            $errorMessage = "";
            switch ($errorCode) {
                case JSON_ERROR_DEPTH:
                    $errorMessage = 'Maximum stack depth exceeded';
                    break;
                case JSON_ERROR_STATE_MISMATCH:
                    $errorMessage = 'Underflow or the modes mismatch';
                    break;
                case JSON_ERROR_CTRL_CHAR:
                    $errorMessage = 'Unexpected control character found';
                    break;
                case JSON_ERROR_SYNTAX:
                    $errorMessage = 'Syntax error, malformed JSON';
                    break;
                case JSON_ERROR_UTF8:
                    $errorMessage = 'Malformed UTF-8 characters, possibly incorrectly encoded';
                    break;
                default:
                    $errorMessage = 'Unknown error';
                    break;
            }
            // Logs a notice.
            \Drupal::logger('exif')->notice(t($errorMessage));
            return [];
        }
    }
    
    /**
     * Handle how to call exiftool.
     *
     * @param string $file
     *   Image to scan.
     * @param bool $enable_sections
     *   Extract sections or not.
     * @param bool $enable_markerNote
     *   Extract marker notes or not (for now, always FALSE)
     * @param bool $enable_non_supported_tags
     *   Extract non supported tags or not (for now, always FALSE)
     *
     * @return string
     *   ExifTool JSON result containing all metadata.
     */
    private function runTool($file, $enable_sections = TRUE, $enable_markerNote = FALSE, $enable_non_supported_tags = FALSE) {
        $params = ' -E -n -json ';
        if ($enable_sections) {
            $params .= '-g -struct ';
        }
        if ($enable_markerNote) {
            $params .= '-fast ';
        }
        else {
            $params .= '-fast2 ';
        }
        if ($enable_non_supported_tags) {
            $params .= '-u -U ';
        }
        // Escape all of the arguments passed to the function.
        // Note: If params is expanded so it is customizable, make sure that each
        // piece is passed through escapeshellarg().
        $commandline = escapeshellcmd(self::getExecutable() . $params . escapeshellarg($file));
        $output = [];
        $returnCode = 0;
        exec($commandline, $output, $returnCode);
        if ($returnCode != 0) {
            $output = "";
            Drupal::logger('exif')->warning(t("exiftool return an error. can not extract metadata from file :file", [
                ':file' => $file,
            ]));
        }
        $info = implode("\n", $output);
        return $info;
    }
    
    /**
     * Translate all keys to lowercase.
     *
     * ExiffTool is case sensitive. the module is not.
     * So we need to lowercase all keys to be able to
     * get the needed values.
     *
     * @param array $data
     *   Values by keys.
     *
     * @return array
     *   same values with lowercase keys.
     */
    private function toLowerJsonResult(array $data) {
        $result = [];
        foreach ($data as $section => $values) {
            if (is_array($values)) {
                $result[strtolower($section)] = array_change_key_case($values);
            }
            else {
                $result[strtolower($section)] = $values;
            }
        }
        return $result;
    }
    
    /**
     * {@inheritdoc}
     */
    public function getFieldKeys() {
        return [];
    }

}