getEpubNavigation function

Navigation getEpubNavigation(EpubPackage package, Archive archive, String? rootFilePath)

Retrieves the navigation of the EPUB from the provided package and archive.

The function first gets the TOC ID from the package, then finds the TOC manifest item with that ID. It then gets the TOC file entry from the archive and parses it into an XML document. Finally, it creates a Navigation object from the container document.

package is the EpubPackage from which to retrieve the TOC ID. archive is the Archive from which to retrieve the TOC file entry. rootFilePath is the root file path of the EPUB.

Returns a Navigation representing the navigation of the EPUB.

Throws an Exception if the TOC ID is empty, the TOC manifest item could not be found, or the TOC file entry could not be found.

Implementation

Navigation getEpubNavigation(
  final EpubPackage package,
  final Archive archive,
  final String? rootFilePath,
) {
  final tocId = package is Epub3Package && package.spine.tocId == null
      ? package.tocId
      : package.spine.tocId;

  if (tocId == null) throw Exception('EPUB parsing error: TOC ID is empty.');

  final tocManifestItem = package.manifest.items.firstWhere(
    (final element) => element.id == tocId,
    orElse: () => throw Exception(
      'EPUB parsing error: TOC item $tocId not found in EPUB manifest.',
    ),
  );

  final contentDirectoryPath = _getDirectoryPath(rootFilePath ?? '');
  final tocFileEntryPath = _combinePaths(
    contentDirectoryPath,
    tocManifestItem.path,
  );

  final tocFileEntry = archive.files.firstWhere(
    (final file) => file.name.toLowerCase() == tocFileEntryPath.toLowerCase(),
    orElse: () => throw Exception(
      'EPUB parsing error: TOC file $tocFileEntryPath not found in archive.',
    ),
  );

  final containerDocument = XmlDocument.parse(
    convert.utf8.decode(tocFileEntry.content as List<int>),
  );
  final navigationContent = Navigation(document: containerDocument);
  return navigationContent;
}