#!/usr/bin/env python3
"""Require the exact reviewed Rust compiler before running Rust quality gates."""

from __future__ import annotations

import re
import subprocess
import sys
import tomllib
from pathlib import Path

ROOT = Path(__file__).resolve().parents[1]
PIN = ROOT / "rust-toolchain.toml"


def main() -> None:
    with PIN.open("rb") as stream:
        expected = tomllib.load(stream)["toolchain"]["channel"]
    result = subprocess.run(
        ["rustc", "--version"],
        check=True,
        capture_output=True,
        text=True,
    )
    match = re.match(r"rustc ([0-9]+\.[0-9]+\.[0-9]+)(?:\s|$)", result.stdout)
    if match is None:
        print(f"FAIL: could not parse compiler version: {result.stdout.strip()}", file=sys.stderr)
        raise SystemExit(1)
    actual = match.group(1)
    if actual != expected:
        print(
            f"FAIL: rustc {actual} is active, but rust-toolchain.toml pins {expected}.\n"
            "A distro-provided cargo/rustc may ignore rust-toolchain.toml; use the "
            "pinned rustup toolchain or update the distro packages.",
            file=sys.stderr,
        )
        raise SystemExit(1)
    print(f"PASS: exact Rust toolchain {actual}")


if __name__ == "__main__":
    main()