import logging
from torchtext.utils import download_from_url, extract_archive
from torchtext.data.datasets_utils import (
    _RawTextIterableDataset,
    _wrap_split_argument,
    _add_docstring_header,
    _find_match,
    _create_dataset_directory,
    _read_text_iterator,
)

URL = 'https://s3.amazonaws.com/research.metamind.io/wikitext/wikitext-2-v1.zip'

MD5 = '542ccefacc6c27f945fb54453812b3cd'

NUM_LINES = {
    'train': 36718,
    'valid': 3760,
    'test': 4358,
}

DATASET_NAME = "WikiText2"


@_add_docstring_header(num_lines=NUM_LINES)
@_create_dataset_directory(dataset_name=DATASET_NAME)
@_wrap_split_argument(('train', 'valid', 'test'))
def WikiText2(root, split):
    dataset_tar = download_from_url(URL, root=root, hash_value=MD5, hash_type='md5')
    extracted_files = extract_archive(dataset_tar)
    path = _find_match(split, extracted_files)
    logging.info('Creating {} data'.format(split))
    return _RawTextIterableDataset(DATASET_NAME,
                                   NUM_LINES[split], _read_text_iterator(path))
