env_bootstrap.py

# file: env_bootstrap.py
from __future__ import annotations
import hashlib
import inspect
import os
import shutil
import subprocess
import sys
from pathlib import Path

# All required packages - no external requirements.txt needed
PACKAGES = [
    "selenium>=4.15.0",
    "python-dotenv>=1.0.0",
    "webdriver-manager>=4.0.0",
]

def _caller_dir() -> Path:
    frm = inspect.stack()[2] if len(inspect.stack()) >= 3 else inspect.stack()[1]
    return Path(frm.filename).resolve().parent

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

def _in_that_venv(venv_dir: Path) -> bool:
    try:
        return Path(sys.prefix).resolve() == venv_dir.resolve()
    except Exception:
        return False

def _hash_packages(packages: list[str]) -> str:
    h = hashlib.sha256()
    h.update("\n".join(sorted(packages)).encode("utf-8"))
    return h.hexdigest()

def ensure_venv(
    venv_name: str = ".venv",
    flag_filename: str = ".deps_ok",
) -> None:
    """
    Ensures:
      1) A venv named `venv_name` exists next to the caller file.
      2) The current process runs using that venv's Python (re-execs if needed).
      3) Installs PACKAGES only once per content-hash, tracked by `flag_filename`.
    """
    caller_dir = _caller_dir()
    venv_dir = caller_dir / venv_name
    vpy = _venv_python(venv_dir)

    # 1) Create venv if missing
    if not venv_dir.exists():
        subprocess.check_call([sys.executable, "-m", "venv", str(venv_dir)])

    # 2) Re-exec under that venv if not already
    if not _in_that_venv(venv_dir):
        os.execv(str(vpy), [str(vpy), *sys.argv])

    # 3) Install packages with hash flag
    flag_path = caller_dir / flag_filename
    current_hash = _hash_packages(PACKAGES)

    flag_ok = False
    try:
        if flag_path.exists():
            saved = flag_path.read_text(encoding="utf-8").strip()
            flag_ok = saved == current_hash
    except Exception:
        flag_ok = False

    if not flag_ok:
        try:
            subprocess.check_call([sys.executable, "-m", "pip", "--version"])
        except subprocess.CalledProcessError:
            pass
        if shutil.which("pip") is None:
            try:
                subprocess.check_call([sys.executable, "-m", "ensurepip", "--upgrade"])
            except Exception:
                pass

        subprocess.check_call([sys.executable, "-m", "pip", "install", *PACKAGES])
        flag_path.write_text(current_hash, encoding="utf-8")

if __name__ == "__main__":
    ensure_venv()