import os
import subprocess
import sys
from pathlib import Path


class VirtualEnvManager:
    def __init__(self, venv_dir: Path, entry_script: Path) -> None:
        self.venv_dir = venv_dir
        self.entry_script = entry_script

    @staticmethod
    def in_virtualenv() -> bool:
        return (
            hasattr(sys, "real_prefix")
            or sys.prefix != getattr(sys, "base_prefix", sys.prefix)
        )

    def _venv_python(self) -> Path:
        if os.name == "nt":
            return self.venv_dir / "Scripts" / "python.exe"
        return self.venv_dir / "bin" / "python"

    def ensure_and_reexec_if_needed(self) -> None:
        if self.in_virtualenv():
            return

        venv_python = self._venv_python()
        if not venv_python.exists():
            subprocess.check_call([sys.executable, "-m", "venv", str(self.venv_dir)])

        os.execv(
            str(venv_python),
            [str(venv_python), str(self.entry_script.resolve()), *sys.argv[1:]],
        )