"""
Role-marked square tokenizer for Chess Challenge.
Each move is represented as: <from_square>_f <to_square>_t [promo?] [EOS]

Examples:
  WPe2e4        -> e2_f e4_t [EOS]
  BPe7e8=Q      -> e7_f e8_t q [EOS]
"""
from __future__ import annotations
import json
import os
import re
from typing import Dict, List, Optional, Tuple, Any
from transformers import PreTrainedTokenizer

_MOVE_RE = re.compile(r"^([WB])([PNBRQK])([a-h][1-8])([a-h][1-8])(.*)$")
_PROMO_RE = re.compile(r"=([QRBNqrbn])")

SQUARES = [f"{f}{r}" for r in "12345678" for f in "abcdefgh"]
PROMOS = ["q", "r", "b", "n"]

class ChessTokenizer(PreTrainedTokenizer):
    model_input_names = ["input_ids", "attention_mask"]
    vocab_files_names = {"vocab_file": "vocab.json"}
    
    PAD_TOKEN = "[PAD]"
    BOS_TOKEN = "[BOS]"
    EOS_TOKEN = "[EOS]"
    UNK_TOKEN = "[UNK]"

    def __init__(
        self,
        vocab_file: Optional[str] = None,
        vocab: Optional[Dict[str, int]] = None,
        **kwargs: Any,
    ):
        self._pad_token = self.PAD_TOKEN
        self._bos_token = self.BOS_TOKEN
        self._eos_token = self.EOS_TOKEN
        self._unk_token = self.UNK_TOKEN
        
        for k in ["pad_token", "bos_token", "eos_token", "unk_token"]:
            kwargs.pop(k, None)
            
        if vocab is not None:
            self._vocab = vocab
        elif vocab_file is not None and os.path.isfile(vocab_file):
            with open(vocab_file, "r", encoding="utf-8") as f:
                self._vocab = json.load(f)
        else:
            self._vocab = self._build_fixed_vocab()
            
        self._ids_to_tokens = {v: k for k, v in self._vocab.items()}
        
        super().__init__(
            pad_token=self._pad_token,
            bos_token=self._bos_token,
            eos_token=self._eos_token,
            unk_token=self._unk_token,
            **kwargs,
        )

    @staticmethod
    def _build_fixed_vocab() -> Dict[str, int]:
        tokens: List[str] = [
            ChessTokenizer.PAD_TOKEN,
            ChessTokenizer.BOS_TOKEN,
            ChessTokenizer.EOS_TOKEN,
            ChessTokenizer.UNK_TOKEN,
        ]
        tokens += [f"{sq}_f" for sq in SQUARES]
        tokens += [f"{sq}_t" for sq in SQUARES]
        tokens += PROMOS
        return {tok: i for i, tok in enumerate(tokens)}

    @property
    def vocab_size(self) -> int:
        return len(self._vocab)

    def get_vocab(self) -> Dict[str, int]:
        return dict(self._vocab)

    @classmethod
    def build_vocab_from_dataset(cls, *args: Any, **kwargs: Any) -> "ChessTokenizer":
        return cls()

    @classmethod
    def build_vocab_from_iterator(cls, *args: Any, **kwargs: Any) -> "ChessTokenizer":
        return cls()

    def _tokenize(self, text: str) -> List[str]:
        """Tokenize a space-separated list of dataset moves into role-marked tokens."""
        text = (text or "").strip()
        if not text:
            return []
            
        out: List[str] = []
        for move in text.split():
            # Allow already-tokenized text (debugging)
            if move in self._vocab:
                out.append(move)
                continue
                
            # Try to match Standard Lichess Format (WPe2e4)
            m = _MOVE_RE.match(move)
            if not m:
                # If it's plain UCI like e2e4 or e7e8q
                if re.fullmatch(r"[a-h][1-8][a-h][1-8][qrbn]?", move):
                    src, dst = move[:2], move[2:4]
                    out.append(f"{src}_f")
                    out.append(f"{dst}_t")
                    if len(move) == 5:
                        out.append(move[4])
                    out.append(self.EOS_TOKEN)
                    continue
                
                # Unknown token
                out.append(self.UNK_TOKEN)
                out.append(self.EOS_TOKEN)
                continue
            
            # Extract parts from WPe2e4...
            _side, _piece, src, dst, suffix = m.groups()
            out.append(f"{src}_f")
            out.append(f"{dst}_t")
            
            promo = None
            pm = _PROMO_RE.search(suffix or "")
            if pm:
                promo = pm.group(1).lower()
            
            if promo in PROMOS:
                out.append(promo)
                
            out.append(self.EOS_TOKEN)
            
        return out

    def _convert_token_to_id(self, token: str) -> int:
        return self._vocab.get(token, self._vocab[self.UNK_TOKEN])

    def _convert_id_to_token(self, index: int) -> str:
        return self._ids_to_tokens.get(index, self.UNK_TOKEN)

    def convert_tokens_to_string(self, tokens: List[str]) -> str:
        return " ".join(tokens)

    def save_vocabulary(self, save_directory: str, filename_prefix: Optional[str] = None) -> Tuple[str]:
        os.makedirs(save_directory, exist_ok=True)
        name = "vocab.json" if not filename_prefix else f"{filename_prefix}-vocab.json"
        path = os.path.join(save_directory, name)
        with open(path, "w", encoding="utf-8") as f:
            json.dump(self._vocab, f, indent=2, ensure_ascii=False)
        return (path,)