from __future__ import annotations

import os
from dataclasses import dataclass
from datetime import timedelta
from functools import lru_cache

from services.security import JWTSettings


@dataclass(frozen=True, slots=True)
class Settings:
    """Application configuration sourced from environment variables."""

    jwt_secret_key: str = "change-me"
    jwt_algorithm: str = "HS256"
    jwt_access_token_minutes: int = 15
    jwt_refresh_token_days: int = 7

    @classmethod
    def from_environment(cls) -> "Settings":
        """Construct settings from environment variables."""

        return cls(
            jwt_secret_key=os.getenv("CALMINER_JWT_SECRET", "change-me"),
            jwt_algorithm=os.getenv("CALMINER_JWT_ALGORITHM", "HS256"),
            jwt_access_token_minutes=cls._int_from_env(
                "CALMINER_JWT_ACCESS_MINUTES", 15
            ),
            jwt_refresh_token_days=cls._int_from_env(
                "CALMINER_JWT_REFRESH_DAYS", 7
            ),
        )

    @staticmethod
    def _int_from_env(name: str, default: int) -> int:
        raw_value = os.getenv(name)
        if raw_value is None:
            return default
        try:
            return int(raw_value)
        except ValueError:
            return default

    def jwt_settings(self) -> JWTSettings:
        """Build runtime JWT settings compatible with token helpers."""

        return JWTSettings(
            secret_key=self.jwt_secret_key,
            algorithm=self.jwt_algorithm,
            access_token_ttl=timedelta(minutes=self.jwt_access_token_minutes),
            refresh_token_ttl=timedelta(days=self.jwt_refresh_token_days),
        )


@lru_cache(maxsize=1)
def get_settings() -> Settings:
    """Return cached application settings."""

    return Settings.from_environment()