# settings.py
# 统一配置入口：所有可变参数都从环境变量 / .env 读取，代码里不再出现硬编码密码。
#
# 真实业务里"配置"和"代码"必须分离：
#   开发 / 测试 / 生产 用的是三套数据库，靠改代码切环境一定会出事故。

import os
from pathlib import Path


BASE_DIR = Path(__file__).resolve().parent


def _load_dotenv(path: Path) -> None:
    """极简 .env 加载器。

    优先使用 python-dotenv；没装则用内置的简易解析，保证零依赖也能跑。
    """
    if not path.exists():
        return
    try:
        from dotenv import load_dotenv  # type: ignore

        load_dotenv(path, override=False)
        return
    except ImportError:
        pass

    for raw in path.read_text(encoding="utf-8").splitlines():
        line = raw.strip()
        if not line or line.startswith("#") or "=" not in line:
            continue
        key, _, value = line.partition("=")
        key, value = key.strip(), value.strip().strip('"').strip("'")
        # 已存在的真实环境变量优先，不被文件覆盖
        os.environ.setdefault(key, value)


_load_dotenv(BASE_DIR / ".env")


def _env(key: str, default: str) -> str:
    value = os.getenv(key)
    return default if value is None or value == "" else value


def _env_bool(key: str, default: bool) -> bool:
    return _env(key, str(default)).strip().lower() in ("1", "true", "yes", "on")


def _env_int(key: str, default: int) -> int:
    try:
        return int(_env(key, str(default)))
    except ValueError:
        return default


class Settings:
    # ---------- 应用 ----------
    APP_NAME: str = _env("APP_NAME", "学生管理系统")
    APP_VERSION: str = _env("APP_VERSION", "1.1.0")
    DEBUG: bool = _env_bool("DEBUG", True)

    HOST: str = _env("HOST", "127.0.0.1")
    PORT: int = _env_int("PORT", 8004)

    # API 统一前缀。改这里就能整体换版本，不用一个个改路由。
    API_PREFIX: str = _env("API_PREFIX", "/api/v1")

    # ---------- 跨域 ----------
    # 注意：allow_credentials=True 时浏览器【禁止】返回 "*"，
    # 必须显式列出前端域名，否则带 Cookie / 登录态一定失败。
    CORS_ORIGINS: list[str] = [
        o.strip()
        for o in _env(
            "CORS_ORIGINS",
            "http://localhost:5500,http://127.0.0.1:5500,"
            "http://localhost:8000,http://127.0.0.1:8000,"
            "http://localhost:5173,http://127.0.0.1:5173",
        ).split(",")
        if o.strip()
    ]

    # ---------- 数据库 ----------
    DB_HOST: str = _env("DB_HOST", "127.0.0.1")
    DB_PORT: int = _env_int("DB_PORT", 3306)
    DB_USER: str = _env("DB_USER", "root")
    DB_PASSWORD: str = _env("DB_PASSWORD", "")
    DB_NAME: str = _env("DB_NAME", "student_management_system")
    DB_CHARSET: str = _env("DB_CHARSET", "utf8mb4")

    DB_ECHO: bool = _env_bool("DB_ECHO", False)
    DB_POOL_SIZE: int = _env_int("DB_POOL_SIZE", 5)
    DB_MAX_OVERFLOW: int = _env_int("DB_MAX_OVERFLOW", 10)
    DB_POOL_RECYCLE: int = _env_int("DB_POOL_RECYCLE", 3600)

    @property
    def database_url(self) -> str:
        from urllib.parse import quote_plus

        return (
            f"mysql+pymysql://{self.DB_USER}:{quote_plus(self.DB_PASSWORD)}"
            f"@{self.DB_HOST}:{self.DB_PORT}/{self.DB_NAME}"
            f"?charset={self.DB_CHARSET}"
        )


settings = Settings()