import os
from pathlib import Path


def _find_config_file():
    """根据环境变量 APP_ENV 查找对应的配置文件

    支持: APP_ENV=local/dev/test/uat/prod -> .env.local / .env.dev / ...
    默认: local
    查找路径优先级:
      1. {package}/config/     (源码路径)
      2. /app/standards_service/config/  (Docker COPY 路径)
      3. /app/config/          (Docker volume 挂载路径)
      4. {cwd}/config/         (工作目录)
    """
    env = os.environ.get("APP_ENV", "local")
    filename = f".env.{env}"

    candidates = [
        Path(__file__).resolve().parent.parent / "config" / filename,
        Path("/app/standards_service/config") / filename,
        Path("/app/config") / filename,
        Path(os.getcwd()) / "config" / filename,
    ]

    for cfg in candidates:
        if cfg.exists():
            return cfg

    return candidates[0]


def _load_env_file(path):
    """从 .env 文件中加载键值对到 os.environ（不覆盖已有变量）。"""
    if not path.exists():
        return
    with open(path, encoding="utf-8") as f:
        for line in f:
            line = line.strip()
            if not line or line.startswith("#"):
                continue
            if "=" in line:
                key, _, value = line.partition("=")
                key = key.strip()
                value = value.strip().strip('"').strip("'")
                if key and key not in os.environ:
                    os.environ[key] = value


def load_config():
    """加载配置，返回配置文件路径。"""
    config_path = _find_config_file()
    _load_env_file(config_path)
    return config_path