class ChessSolver(dspy.Signature):
    """From the set of allowed moves, pick the next best move for this chess puzzle."""
    puzzle: str = dspy.InputField(description="The current state of the board, represented as a FEN string.")
    allowed_moves: list[str] = dspy.InputField(description="The set of allowed moves for the current player.")
    solution: str = dspy.OutputField(description="The next move to make, represented as a UCI string.")

def metric_with_feedback(example, prediction, trace=None, pred_name=None, pred_trace=None):
    llm_answer = prediction.solution
    correct_move = example['solution']
    board = chess.Board(example['puzzle'])

    llm_answer_score = shallow_score_of_moves([llm_answer], board)[0]
    board.push(chess.Move.from_uci(llm_answer))
    best_counter_move = get_best_legal_counter_move_by_opponent(board)
    feedback_text = ""

    if correct_move != prediction.solution:
        feedback_text = f"The move is not the best move (best move is {correct_move}). The best counter move for {llm_answer} from the opponent is {best_counter_move}. Also stockfish score (negative is bad, positive is good) for {llm_answer} is {llm_answer_score}."  
    else: 
        feedback_text = "Perfect! The move is a good move."

    return dspy.Prediction(score=int(correct_move == prediction.solution), feedback=feedback_text)

Task
Choose the single best move from a provided restricted set in a chess puzzle and justify it with precise, verified calculation from the given FEN.

Inputs
- puzzle: a FEN string describing the full position.
- allowed_moves: a set of legal candidate moves in UCI notation (e.g., g8h8, f8f7, c4f1, e7e8q for a promotion).

Output (exact format)
- reasoning: a concise, factual justification of why your chosen move is best among the allowed options. State the key idea(s) and, when relevant, the opponent’s best reply and one short principal variation (PV).
- solution: the chosen move in UCI notation, exactly matching one of the allowed_moves.

Board parsing and verification (mandatory)
1) Parse the FEN fully before calculating:
   - Field 1 (piece placement): ranks 8→1, files a→h; digits are consecutive empty squares; pieces: KQBNRP (white), kqbnrp (black).
   - Field 2 (side to move): w or b (determine whose turn it is).
   - Field 3 (castling rights): any of KQkq or "-" if none (rights must exist and be legally usable for castling moves).
   - Field 4 (en passant target square): a square like e6 or "-" if none (only relevant if an EP capture is possible now).
   - Fields 5–6: halfmove clock and fullmove number (generally irrelevant to tactics).
2) Reconstruct the board map:
   - Place all pieces correctly and locate both kings.
   - Confirm side to move.
   - Note castling and EP rights if any candidate could involve them or be affected by them.
3) UCI move rules you must respect:
   - UCI is from-square + to-square, plus optional promotion piece letter (q/r/b/n) for pawn promotions (e.g., e7e8q).
   - Castling is the king move in UCI: e1g1, e1c1, e8g8, e8c8; ensure:
     - Castling right exists from FEN.
     - All traversed squares are empty.
     - The king does not start, pass through, or end in check.
   - En passant is only legal if FEN EP target matches the capture square and the capturing pawn’s move matches EP rules; encode as from-to (no suffix).
   - If a promotion is among allowed moves, ensure the pawn is on the 7th (white) or 2nd (black) rank and the destination is the last rank.

Hard rules
1) Never output a move that is not in allowed_moves. The solution string must exactly equal one of the provided UCI moves (including correct promotion letter if applicable).
2) Verify every tactical and legal claim against the reconstructed board:
   - A “capture” only if the destination square currently contains an opponent piece (or is the EP target when EP is legal). Identify the captured piece and square correctly.
   - A “check” only if, after the move, the opponent king is actually attacked. State the attacking line/pattern (e.g., discovered check, rook along file with no blockers, knight L-jump).
   - A “mate” only if no legal defense exists. Explicitly consider:
     - All king moves (confirm destination squares are not occupied by own pieces and not attacked).
     - All possible interpositions on the checking line by any legal piece.
     - All legal captures of the checking piece (including en passant when relevant) and recaptures.
   - Confirm piece movement legality and clear paths for sliders (queen/rook/bishop).
   - Confirm square identities and sides (avoid misidentifying pieces or colors).
3) Evaluate the allowed moves by concrete calculation first:
   - Prioritize forcing moves: checks > captures > strong threats > quiet moves.
   - For each candidate, test the opponent’s best defense at least one move deep; if the line remains forcing or tactically critical, extend another move or two.
   - Always check for simple, strong defensive resources (king flights, interpositions, counterchecks, captures).
   - Compare outcomes by:
     - Immediate material result (clean wins/losses, forcing forks, pins, skewers).
     - King safety and attack continuity (forced mates, perpetuals avoided/forced).
     - Unstoppable threats (promotion, decisive invasion).
     - Conversion prospects (passed pawns, piece activity, coordination).
   - Do not prefer a “safe-looking” quiet move over a forcing win; validate by calculation. Conversely, avoid tempting but unsound tactics if the opponent has a clear refutation.
4) Special cases and tie-breakers:
   - If only one allowed move is given, select it (you may note it’s the only allowed move).
   - If two candidates are strong, choose the one that is more forcing or yields a more durable, unavoidable advantage (e.g., forced mate or clear material gain).
   - Do not dismiss a forcing line on vague “king safety” grounds; either refute it concretely or accept it if it stands.
5) Style and constraints:
   - Be concise and factual. Do not include engine scores or vague claims.
   - Include a brief PV for tactical/forcing positions: your move, opponent’s best reply, and one or two key follow-up moves.
   - Use precise square references and correct piece identities based on the FEN.
   - Output format must be exactly:
     reasoning: <short, factual justification with key line(s)>
     solution: <best move in UCI notation>

Domain reminders and common pitfalls (avoid them)
- Confirm the side to move from the FEN; never assume.
- Verify sliding paths are clear before asserting a check/capture.
- Before claiming a capture or check (e.g., Qg7+, Nxg5, Rxd8), confirm the piece can legally reach the destination and the line is not blocked.
- When asserting mate, systematically eliminate: king moves, interpositions, and captures (including unusual ones like EP when legal).
- Promotions must include the correct UCI promotion letter (q/r/b/n); ensure the pawn starts on the correct rank and reaches the last rank.
- En passant is only legal when the FEN’s EP square enables it in that exact ply.
- Among allowed moves, prefer decisive forcing tactics (e.g., immediate checkmate or winning material) over “safer-looking” non-forcing moves; verify by calculating the opponent’s best reply, not a cooperative one.

Decision/verification checklist before finalizing
- Parsed FEN fields correctly; board and side to move verified.
- Legalities checked: move pattern, occupancy, pins (king not left in check), castling/EP specifics where relevant.
- Forcing lines examined for each allowed move; opponent’s strongest defense considered.
- If claiming check/mate/material win, verified with explicit lines and defenses refuted.
- Chosen move is in allowed_moves and encoded correctly in UCI (with promotion when applicable).
- reasoning is concise, factual, includes one short PV and the key idea(s).