class SvgSpriteExtractor

class SvgSpriteExtractor extends IconExtractorWithFinder {
  
  /**
   * {@inheritdoc}
   */
  public function discoverIcons() : array {
    $files = $this->getFilesFromSources();
    if (empty($files)) {
      return [];
    }
    $icons = [];
    foreach ($files as $file) {
      $icon_ids = $this->extractIdsFromXml($file['absolute_path'] ?? '');
      foreach ($icon_ids as $icon_id) {
        $id = IconDefinition::createIconId($this->configuration['id'], (string) $icon_id);
        $icons[$id] = [
          'absolute_path' => $file['absolute_path'],
          'source' => $file['source'],
          'group' => $file['group'] ?? NULL,
        ];
      }
    }
    return $icons;
  }
  
  /**
   * Extract icon ID from XML.
   *
   * @param string $source
   *   Local path or url to the svg file.
   *
   * @return array
   *   A list of icons with keys:
   *   - icon_ids: array of icon Id found
   *   - attributes: Attribute object from the svg
   */
  private function extractIdsFromXml(string $source) : array {
    if (!($content = $this->iconFinder
      ->getFileContents($source))) {
      return [];
    }
    libxml_use_internal_errors(TRUE);
    if (!($svg = simplexml_load_string((string) $content))) {
      // @todo do we need to log a warning with the xml error?
      return [];
    }
    return $this->extractIdsFromSymbols($svg->symbol) ?: $this->extractIdsFromSymbols($svg->defs->symbol ?? NULL);
  }
  
  /**
   * Extract icon ID from SVG symbols.
   *
   * @param \SimpleXMLElement|null $wrapper
   *   A SVG element.
   *
   * @return array
   *   A list of icons ID.
   */
  private function extractIdsFromSymbols(?\SimpleXMLElement $wrapper) : array {
    if ($wrapper === NULL) {
      return [];
    }
    $ids = [];
    foreach ($wrapper as $symbol) {
      if (isset($symbol['id']) && 0 === preg_match('/[^\\w-]/', (string) $symbol['id'])) {
        $ids[] = (string) $symbol['id'];
      }
    }
    return $ids;
  }

}