import csv
import gzip
from typing import Any, Dict, List, Tuple

import datasets

logger = datasets.logging.get_logger(__name__)

_DESCRIPTION = """\
This dataset is used for AIO (AI王), a competition to promote research on question answering systems \
for the Japanese language. This dataset contains passages, each of which consists of consecutive sentences 
no longer than 400 characters from Japanese Wikipedia as of 2022-04-04.
"""

_URL = "https://github.com/cl-tohoku/quiz-datasets"
_URLS = {
    "small": "https://github.com/cl-tohoku/quiz-datasets/releases/download/v1.0.0/dpr.wikipedia_split.jawiki-20220404-c400-small.tsv.gz",
    "medium": "https://github.com/cl-tohoku/quiz-datasets/releases/download/v1.0.0/dpr.wikipedia_split.jawiki-20220404-c400-medium.tsv.gz",
    "large": "https://github.com/cl-tohoku/quiz-datasets/releases/download/v1.0.0/dpr.wikipedia_split.jawiki-20220404-c400-large.tsv.gz",
}


class JaWiki20220404Passages(datasets.GeneratorBasedBuilder):

    BUILDER_CONFIGS = [datasets.BuilderConfig(name=key) for key in _URLS.keys()]

    def _info(self) -> datasets.DatasetInfo:
        return datasets.DatasetInfo(
            description=_DESCRIPTION,
            features=datasets.Features(
                {
                    "id": datasets.Value("int32"),
                    "text": datasets.Value("string"),
                    "title": datasets.Value("string"),
                }
            ),
            homepage="https://github.com/cl-tohoku/quiz-datasets",
        )

    def _split_generators(self, dl_manager: datasets.DownloadManager) -> List[datasets.SplitGenerator]:
        downloaded_file = dl_manager.download(_URLS[self.config.name])
        return [
            datasets.SplitGenerator(
                name=datasets.Split.TRAIN,
                gen_kwargs={"filepath": downloaded_file},
            )
        ]

    def _generate_examples(self, filepath: str) -> Tuple[str, Dict[str, Any]]:
        logger.info(f"generating examples from {filepath}")

        with gzip.open(filepath, "rt", encoding="utf-8") as f:
            reader = csv.DictReader(f, delimiter="\t")
            # the tsv file has a header [id, title, text]
            for key, data in enumerate(reader):
                yield key, data