import io
import logging
from datasets import (
    GeneratorBasedBuilder,
    DatasetInfo,
    SplitGenerator,
    Split,
    DownloadManager,
    Features,
    Value,
    Array2D,
    Sequence,
)
import chess
from adversarial_gym.chess_env import ChessEnv
import zstandard as zstd



class ChessPGNDataset(GeneratorBasedBuilder):
    VERSION = "0.0.1"

    def _info(self):
        return DatasetInfo(
            description="Chess positions + moves + results, streamed from PGN shards",
            features=Features({
                "state":       Array2D((8,8), dtype="int8"),
                "action":      Value("int16"),
                "best_action": Value("int16"),  # -1 if not available
                "legal_actions": Sequence(Value("int16")),
                "result":      Value("float32"),
            })
        )

    def _split_generators(self, dl_manager: DownloadManager):
        from pathlib import Path
        import os

        if self.config.data_dir:
            repo_root = Path(self.config.data_dir)
            train_files = [repo_root / 'train' / f for f in os.listdir(repo_root / 'train')]
            test_files  = [repo_root / 'test'  / f for f in os.listdir(repo_root / 'test')]

        elif self.config.data_files:
            train_files = self.config.data_files["train"]
            test_files  = self.config.data_files["test"]

        train_paths = dl_manager.download(train_files)
        test_paths  = dl_manager.download(test_files)

        return [
            SplitGenerator(
                name=Split.TRAIN,
                gen_kwargs={"shards": train_paths},
            ),
            SplitGenerator(
                name=Split.TEST,
                gen_kwargs={"shards": test_paths},
            ),
        ]
    
    @staticmethod
    def _parse_comment(comment, board):
        """Parse a move comment like '-0.2779' or '0.52 e2e4'.
        Returns (q_val or None, best_action or -1).
        q_val is float in [-1, 1] relative to side-to-move.
        best_action is the action index of the best move, or -1 if absent."""
        if not comment:
            return None, -1
        parts = comment.split()
        if not parts:
            return None, -1
        # First token must be a number in [-1, 1]
        first = parts[0]
        try:
            q_val = float(first)
        except ValueError:
            return None, -1
        if not (-1.0 <= q_val <= 1.0):
            return None, -1
        if len(parts) < 2:
            return q_val, -1
        # Second token is a UCI best move — must be valid and legal
        try:
            best_move = chess.Move.from_uci(parts[1])
            if best_move not in board.legal_moves:
                return q_val, -1
        except Exception:
            return q_val, -1
        best_action = int(ChessEnv.move_to_action(best_move))
        return q_val, best_action

    def _generate_examples(self, shards):
        import chess.pgn
        uid = 0

        for path in shards:
            decompressor = zstd.ZstdDecompressor()
            with open(path, "rb") as compressed:
                with decompressor.stream_reader(compressed) as reader:
                    text_stream = io.TextIOWrapper(reader, encoding='utf-8')
                    while (game := chess.pgn.read_game(text_stream)) is not None:
                        board = game.board()
                        header_result = {"1-0":1,"0-1":-1}.get(game.headers.get("Result",""), 0)
                        for node in game.mainline():
                            move = node.move
                            # Parse annotated Q-value and best move from comment
                            q_val, best_action = self._parse_comment(node.comment, board)
                            if q_val is not None:
                                result = q_val
                            else:
                                result = float(header_result * (-1 if board.turn == 0 else 1))
                            state  = ChessEnv.get_piece_configuration(board)
                            state  = state if board.turn else -state
                            action = ChessEnv.move_to_action(move)
                            legal = [int(ChessEnv.move_to_action(m)) for m in board.legal_moves]
                            yield uid, {
                                "state":       state.astype("int8"),
                                "action":      int(action),
                                "best_action": int(best_action),
                                "legal_actions": legal,
                                "result":      float(result),
                            }
                            uid += 1
                            board.push(move)