XFOIL MCP Server

"""Core helpers for running XFOIL.""" from __future__ import annotations import csv import os import subprocess import tempfile from collections.abc import Iterable from pathlib import Path from .models import PolarRequest, PolarResponse XFOIL_BIN = os.environ.get("XFOIL_BIN", "xfoil") def compute_polar(request: PolarRequest) -> PolarResponse: """Run XFOIL with the provided parameters and return a CSV payload.""" script, polar_path = _prepare_script(request) try: result = subprocess.run( [XFOIL_BIN], input=script.encode("utf-8"), cwd=polar_path.parent, check=False, capture_output=True, ) except FileNotFoundError as exc: # pragma: no cover raise RuntimeError("XFOIL binary not found") from exc if not polar_path.exists(): raise RuntimeError( "XFOIL did not create the polar output", ) if result.returncode != 0: # XFOIL often exits with code 2 even when the polar file is valid. We keep # the output but annotate the CSV with a comment so downstream users are # aware of the non-zero status. warning_comment = f"# xfoil exit code {result.returncode}" else: warning_comment = None lines = polar_path.read_text(encoding="utf-8").splitlines() if warning_comment: lines.insert(0, warning_comment) rows = list(csv.reader(lines)) if rows and rows[0] and "alpha" not in rows[0][0].lower(): rows.insert(0, ["alpha", "CL", "CD", "CM"]) csv_text = "\n".join(",".join(row) for row in rows) return PolarResponse(csv=csv_text) def _prepare_script(request: PolarRequest) -> tuple[str, Path]: tmpdir = Path(tempfile.mkdtemp(prefix="xfoil_mcp_")) airfoil_path = tmpdir / f"{request.airfoil_name}.dat" polar_path = tmpdir / "polar.txt" airfoil_path.write_text(request.airfoil_data, encoding="utf-8") airfoil_name = airfoil_path.name polar_name = polar_path.name commands: Iterable[str] = [ f"LOAD {airfoil_name}", "PANE", "OPER", f"VISC {request.reynolds}", f"MACH {request.mach}", f"ITER {request.iterations}", "PACC", polar_name, "", ] alpha_cmds = [f"ALFA {alpha}" for alpha in request.alphas] if not alpha_cmds: raise RuntimeError("At least one angle of attack must be supplied") footer = ["PACC", "", "QUIT"] script = "\n".join([*commands, *alpha_cmds, *footer]) + "\n" return script, polar_path __all__ = ["compute_polar", "XFOIL_BIN"]