#!/usr/bin/env python3
"""Run a command with one or more Docker-style env files.

Values are parsed literally rather than sourced by a shell.  Tokens containing
`$`, `#`, spaces or shell metacharacters therefore remain unchanged.
"""

from __future__ import annotations

import os
import pathlib
import sys


def load_env(path: pathlib.Path) -> None:
    if not path.is_file():
        raise SystemExit(f"secret environment file is missing: {path}")
    for raw in path.read_text(encoding="utf-8").splitlines():
        line = raw.strip()
        if not line or line.startswith("#"):
            continue
        if line.startswith("export "):
            line = line[7:].lstrip()
        if "=" not in line:
            raise SystemExit(f"invalid environment line in {path}: {raw!r}")
        key, value = line.split("=", 1)
        key = key.strip()
        if not key or not key.replace("_", "A").isalnum() or key[0].isdigit():
            raise SystemExit(f"invalid environment variable in {path}: {key!r}")
        value = value.strip()
        if len(value) >= 2 and value[0] == value[-1] and value[0] in "\"'":
            value = value[1:-1]
        os.environ[key] = value


def main() -> None:
    if len(sys.argv) < 3:
        raise SystemExit("usage: run-with-env ENV_FILE [ENV_FILE ...] -- COMMAND [ARG ...]")
    try:
        separator = sys.argv.index("--")
    except ValueError as exc:
        raise SystemExit("missing -- before command") from exc
    env_files = [pathlib.Path(item) for item in sys.argv[1:separator]]
    command = sys.argv[separator + 1 :]
    if not env_files or not command:
        raise SystemExit("at least one env file and a command are required")
    for env_file in env_files:
        load_env(env_file)
    os.execvp(command[0], command)


if __name__ == "__main__":
    main()