// Helper function to convert FileSystemFileEntry to File
const getFileFromEntry = (fileEntry: FileSystemFileEntry): Promise<File> => {
  return new Promise((resolve) => {
    fileEntry.file(resolve);
  });
};

// Helper function to read all entries in a directory
const readAllDirectoryEntries = async (
  dirReader: FileSystemDirectoryReader
): Promise<FileSystemEntry[]> => {
  const entries: FileSystemEntry[] = [];

  let readBatch: FileSystemEntry[] = [];
  do {
    readBatch = await new Promise<FileSystemEntry[]>((resolve, reject) => {
      try {
        dirReader.readEntries(resolve, reject);
      } catch (e) {
        const error = e as Error;
        reject(error);
      }
    });
    entries.push(...readBatch);
  } while (readBatch.length > 0);

  return entries;
};

// Helper function to process files and folder contents
export async function processDroppedItems(
  dataTransferItems: DataTransferItem[]
): Promise<File[]> {
  const files: File[] = [];

  const processFileSystemEntry = async (
    entry: FileSystemEntry
  ): Promise<void> => {
    if (entry.isFile) {
      const file = await getFileFromEntry(entry as FileSystemFileEntry);
      // drag and dropped files do not have a webkitRelativePath property,
      // but they do have a fullPath property which has the same information
      // https://github.com/ant-design/ant-design/issues/16426
      if (entry.fullPath && !file.webkitRelativePath) {
        Object.defineProperties(file, {
          webkitRelativePath: {
            writable: true,
          },
        });

        // intentionally overwriting webkitRelativePath
        // @ts-expect-error
        file.webkitRelativePath = entry.fullPath.replace(/^\//, '');

        Object.defineProperties(file, {
          webkitRelativePath: {
            writable: false,
          },
        });
      }
      files.push(file);
    } else if (entry.isDirectory) {
      const dirReader = (entry as FileSystemDirectoryEntry).createReader();
      const dirEntries = await readAllDirectoryEntries(dirReader);
      await Promise.all(dirEntries.map(processFileSystemEntry));
    }
  };

  // Filter out and process files from the data transfer items
  await Promise.all(
    dataTransferItems
      .reduce<FileSystemEntry[]>((acc, item) => {
        const entry = item.webkitGetAsEntry();
        return item.kind === 'file' && entry ? [...acc, entry] : acc;
      }, [])
      .map(processFileSystemEntry)
  );

  return files;
}