#%%
import datasets
import zstandard as zstd
import io

#%%
class LichessConfig(datasets.BuilderConfig):
    def __init__(self, features, **kwargs):
        super(LichessConfig, self).__init__(**kwargs)
        self.features = features


class Lichess(datasets.GeneratorBasedBuilder):
    BUILDER_CONFIG_CLASS = LichessConfig
    BUILDER_CONFIGS = [LichessConfig(name="pgn",
                                     features=["WhiteElo",
                                               "BlackElo",
                                               "pgn"]),

                       LichessConfig(name="fen",
                                     features=["WhiteElo",
                                               "BlackElo",
                                               "fens",
                                               "moves",
                                               "scores"]),]

    def _info(self):
        features_dict = {feature: datasets.Value("uint16") for feature in self.config.features}

        if self.config.name == "pgn":
            features_dict["pgn"] = datasets.Value("string")
        
        
        if self.config.name == "fen":
            features_dict["fens"] = datasets.Value("string")
            features_dict["moves"] = datasets.Value("string")
            features_dict["scores"] = datasets.Value("string")

        info = datasets.DatasetInfo(datasets.Features(features_dict))
        return info

    def _get_filepaths(self):
        #months = ["01", "02", "03", "04", "05", "06",
        #          "07", "08", "09", "10", "11", "12"]
        months = ["04"]
        shards = ["0", "1", "2", "3"]
        filepaths = [ self.config.name + "/2023/" + m for m in months]

        if self.config.name == "pgn":
            paths = []
            for shard in shards:
                paths.extend([filepath + "/" + shard + ".zst" for filepath in filepaths])
        
        if self.config.name == "fen":
            paths = []
            for shard in shards:
                paths.extend([filepath + "/" + shard + "_fen.zst" for filepath in filepaths])
        
        return paths

    def _split_generators(self, dl_manager: datasets.DownloadManager):
        filepaths = self._get_filepaths()
        downloaded_files = dl_manager.download(filepaths)
        generator = datasets.SplitGenerator(name=datasets.Split.TRAIN,
                                            gen_kwargs={'filepaths': downloaded_files})
        return [generator]

    def _generate_examples(self, filepaths):
        dctx = zstd.ZstdDecompressor()
        for filepath in filepaths:
            n = 0
            with open(filepath, "rb") as file:
                with dctx.stream_reader(file) as sr:
                    pgn = io.TextIOWrapper(sr)

                    if self.config.name == "pgn":
                        while True:
                            white_elo, black_elo = pgn.readline().split(" ")
                            game_pgn = pgn.readline()
                            next_line = pgn.readline()

                            if game_pgn:
                                _id = n
                                n += 1
                                yield _id, {"WhiteElo": int(white_elo),
                                            "BlackElo": int(black_elo),
                                            "pgn": game_pgn}
                            else:
                                break
                    
                    elif self.config.name == "fen":
                        while True:
                            white_elo, black_elo = pgn.readline().split(" ")
                            game = pgn.readline()
                            fens, moves, scores = game.split(";")

                            if game:
                                _id = n
                                n += 1
                                yield _id, {"WhiteElo": white_elo,
                                            "BlackElo": black_elo,
                                            "fens": fens,
                                            "moves": moves,
                                            "scores": scores}
                            else:
                                break