"""全局配置：pydantic-settings，全部来自环境变量 / .env。

规则（docs/technical-review.md §1.3）：
- 密钥不得硬编码；SECRET_KEY 缺失或仍为模板值时，生产环境拒绝启动。
- DATABASE_URL 可切换 PostgreSQL（扩展接口 1）。
"""

from functools import lru_cache
from pathlib import Path

from pydantic import Field
from pydantic_settings import BaseSettings, SettingsConfigDict

_TEMPLATE_MARKERS = ("change-me",)


class Settings(BaseSettings):
    model_config = SettingsConfigDict(env_file=".env", env_file_encoding="utf-8", extra="ignore")

    # --- 基础 ---
    environment: str = "local"  # local / production
    secret_key: str = Field(min_length=16)

    # --- 数据库 ---
    database_url: str = "sqlite:///./data/app.db"

    # --- 文件存储 ---
    storage_root: str = "./data"

    # --- 套餐 ---
    default_storage_quota: int = 104_857_600   # 100 MB
    default_max_file_size: int = 20_971_520    # 20 MB

    # --- 限流 ---
    rate_limit_per_token_per_min: int = 60
    rate_limit_per_ip_per_min: int = 30

    # --- CORS ---
    frontend_origin: str = "http://localhost:5173"

    @property
    def is_production(self) -> bool:
        return self.environment == "production"

    @property
    def storage_root_path(self) -> Path:
        return Path(self.storage_root).resolve()

    def validate_secrets(self) -> None:
        """生产环境禁止携带模板密钥启动。"""
        if not self.is_production:
            return
        for field_name in ("secret_key",):
            value = getattr(self, field_name).lower()
            if any(marker in value for marker in _TEMPLATE_MARKERS):
                raise RuntimeError(
                    f"配置错误：{field_name} 仍为模板值，生产环境禁止启动。"
                    "请运行: python -c \"import secrets; print(secrets.token_urlsafe(48))\""
                )


@lru_cache
def get_settings() -> Settings:
    s = Settings()  # type: ignore[call-arg]
    s.validate_secrets()
    return s