chess_vision_tool.py

# ======================================================
# ChessPositionSolverTool
#   • Uses chessvision.ai’s open-source detector to turn a board image into FEN
#   • Feeds that FEN to Stockfish (via python-chess) and returns best move in
#     short algebraic notation (e.g. “Qh5#”)
#   • Requires:
#       pip install chessvision python-chess opencv-python
#       and Stockfish binary in PATH (adjust `STOCKFISH_PATH` if needed)
# ======================================================

import requests, cv2, numpy as np, os, subprocess, json, tempfile
from pydantic import BaseModel, Field
from langchain_core.tools import tool
import chess, chess.engine
from chesscog import Chesscog                       # <- pip install chesscog

STOCKFISH_PATH = os.getenv("STOCKFISH_PATH", "stockfish")  # apt-get install stockfish

class ChessInput(BaseModel):
    image_url: str = Field(..., description="PNG/JPG of the chess position")
    stockfish_depth: int = Field(18, ge=10, le=30,
                                 description="Search depth for Stockfish")

@tool(args_schema=ChessInput)
def chess_position_solver(image_url: str, stockfish_depth: int = 18) -> str:
    """
    Converts a chessboard image to FEN with chesscog, sends it to Stockfish,
    and returns the best move in algebraic notation (e.g. 'Rxf2+').
    """
    try:
        # 1 - download image
        img_bytes = requests.get(image_url, timeout=30).content
        img = cv2.imdecode(np.frombuffer(img_bytes, np.uint8), cv2.IMREAD_COLOR)

        # 2 - infer FEN with chesscog
        detector = Chesscog(device="cpu")           # auto-downloads model weights
        fen = detector.get_fen(img)
        if fen is None:
            return "chess_position_solver failed: board not recognised."

        board = chess.Board(fen)

        # 3 - Stockfish
        engine = chess.engine.SimpleEngine.popen_uci(STOCKFISH_PATH)
        result = engine.play(board, chess.engine.Limit(depth=stockfish_depth))
        engine.quit()

        best_move_san = board.san(result.move)      # algebraic, e.g. 'Qh5#'
        return best_move_san

    except Exception as e:
        return f"chess_position_solver failed: {e}"