#!/usr/bin/env python3
"""Deploy-time master password (emergency fallback for web + Qt).

Read order:
  1. BUTTONTASK_MASTER_PASSWORD environment variable
  2. <config>/.master file (created once at deploy via bt-set-master)

The file is not part of OTA packages and is not committed to git.
"""
import os
from pathlib import Path

from config_store import config_path

MASTER_FILENAME = ".master"


def master_password_path():
    env = os.environ.get("BUTTONTASK_MASTER_FILE")
    if env:
        return Path(env)
    return config_path().parent / MASTER_FILENAME


def load_master_password():
    env = (os.environ.get("BUTTONTASK_MASTER_PASSWORD") or "").strip()
    if env:
        return env
    path = master_password_path()
    try:
        if path.is_file():
            return path.read_text(encoding="utf-8").strip()
    except OSError:
        pass
    return ""