# app/config.py
import os
from functools import lru_cache


class Settings:
    """
    后端配置：
    - APP_ENV: dev / prod
    - DB_*: 数据库连接参数
    - 默认库：dev 用 LLZQ-test；prod 用 LLZQ
    """

    def __init__(self) -> None:
        self.app_env = os.getenv("APP_ENV", "dev").lower()

        self.db_host = os.getenv("DB_HOST", "127.0.0.1")
        self.db_port = int(os.getenv("DB_PORT", "5432"))
        self.db_user = os.getenv("DB_USER", "local-Python")
        self.db_password = os.getenv("DB_PASSWORD", "")

        # 默认连接的库，根据 APP_ENV 决定
        if self.app_env == "prod":
            self.db_name_default = "LLZQ"
        else:
            self.db_name_default = "LLZQ-test"

        self.db_schema = os.getenv("DB_SCHEMA", "XCX")

    def resolve_db_name(self, env_header: str | None) -> str:
        """
        根据前端传来的 X-LLZQ-Env 决定最终使用哪个 DB：
        - "prod" => LLZQ
        - 其它/为空 => LLZQ-test
        """
        if env_header is None:
            return self.db_name_default

        env_header = env_header.lower()
        if env_header == "prod":
            return "LLZQ"
        else:
            return "LLZQ-test"


@lru_cache()
def get_settings() -> Settings:
    return Settings()