#!/usr/bin/env python3
"""
Print the nixosConfigurations defined in flake.nix.

Parses flake.nix directly (no `nix eval`, so it works without nix tooling
and is fast).  Brace-matches to find the closing `}` of nixosConfigurations
so it handles nested attrsets correctly.
"""

import re
import sys
from pathlib import Path


def list_hosts(flake_path: Path) -> list[str]:
    src = flake_path.read_text()
    m = re.search(r"nixosConfigurations\s*=\s*\{", src)
    if not m:
        return []

    # Brace-match to find the matching closing }.
    depth, i, close = 0, m.end() - 1, None
    while i < len(src):
        c = src[i]
        if c == "{":
            depth += 1
        elif c == "}":
            depth -= 1
            if depth == 0:
                close = i
                break
        i += 1

    block = src[m.end():close] if close is not None else ""
    return re.findall(
        r"^[ \t]*([A-Za-z_][\w-]*)\s*=\s*nixpkgs\.lib\.nixosSystem",
        block,
        re.M,
    )


def main() -> int:
    flake = Path(sys.argv[1]) if len(sys.argv) > 1 else Path("flake.nix")
    if not flake.is_file():
        print(f"[-] not a file: {flake}", file=sys.stderr)
        return 1
    for name in list_hosts(flake):
        print(name)
    return 0


if __name__ == "__main__":
    sys.exit(main())