import os


def _read_secret(env_var: str, secret_file_var: str, default: str) -> str:
    """Read a config value from env var, or from a Docker secrets file."""
    value = os.environ.get(env_var)
    if value:
        return value
    secret_file = os.environ.get(secret_file_var)
    if secret_file:
        try:
            with open(secret_file) as f:
                return f.read().strip()
        except FileNotFoundError:
            pass
    return default


class Config:
    DATABASE_URL: str = _read_secret(
        "DATABASE_URL",
        "DATABASE_URL_FILE",
        "postgresql+asyncpg://fabled:fabled@localhost:5432/fabledassistant",
    )
    SECRET_KEY: str = _read_secret("SECRET_KEY", "SECRET_KEY_FILE", "dev-secret-change-me")
    SECURE_COOKIES: bool = os.environ.get("SECURE_COOKIES", "").lower() in ("1", "true", "yes")
    LOG_LEVEL: str = os.environ.get("LOG_LEVEL", "INFO")
    LOG_RETENTION_DAYS: int = int(os.environ.get("LOG_RETENTION_DAYS", "90"))

    # SMTP defaults (overridden by DB settings when configured via admin UI)
    SMTP_HOST: str = os.environ.get("SMTP_HOST", "")
    SMTP_PORT: int = int(os.environ.get("SMTP_PORT", "587"))
    SMTP_USERNAME: str = os.environ.get("SMTP_USERNAME", "")
    SMTP_PASSWORD: str = _read_secret("SMTP_PASSWORD", "SMTP_PASSWORD_FILE", "")
    SMTP_FROM_ADDRESS: str = os.environ.get("SMTP_FROM_ADDRESS", "")
    SMTP_FROM_NAME: str = os.environ.get("SMTP_FROM_NAME", "Fabled Scribe")
    SMTP_USE_TLS: bool = os.environ.get("SMTP_USE_TLS", "true").lower() in ("1", "true", "yes")
    BASE_URL: str = os.environ.get("BASE_URL", "http://localhost:5000").rstrip("/")
    TRUST_PROXY_HEADERS: bool = os.environ.get("TRUST_PROXY_HEADERS", "").lower() in ("1", "true", "yes")

    # OIDC / OAuth2 SSO (e.g. Authentik)
    OIDC_ISSUER: str = os.environ.get("OIDC_ISSUER", "")
    OIDC_CLIENT_ID: str = os.environ.get("OIDC_CLIENT_ID", "")
    OIDC_CLIENT_SECRET: str = _read_secret("OIDC_CLIENT_SECRET", "OIDC_CLIENT_SECRET_FILE", "")
    OIDC_SCOPES: str = os.environ.get("OIDC_SCOPES", "openid profile email")
    LOCAL_AUTH_ENABLED: bool = os.environ.get("LOCAL_AUTH_ENABLED", "true").lower() not in ("0", "false", "no")

    # SearXNG web search (external instance). Currently only surfaced via
    # /api/settings/search for the Integrations tab's status indicator —
    # the MCP layer doesn't proxy web search (Claude has its own).
    SEARXNG_URL: str = os.environ.get("SEARXNG_URL", "")

    @classmethod
    def oidc_enabled(cls) -> bool:
        return bool(cls.OIDC_ISSUER and cls.OIDC_CLIENT_ID and cls.OIDC_CLIENT_SECRET)

    @classmethod
    def searxng_enabled(cls) -> bool:
        return bool(cls.SEARXNG_URL)

    @classmethod
    def validate(cls) -> None:
        """Validate critical config values at startup. Raises ValueError on misconfiguration."""
        errors: list[str] = []
        if cls.LOG_RETENTION_DAYS < 1:
            errors.append(f"LOG_RETENTION_DAYS={cls.LOG_RETENTION_DAYS} must be >= 1")
        if not (1 <= cls.SMTP_PORT <= 65535):
            errors.append(f"SMTP_PORT={cls.SMTP_PORT} must be between 1 and 65535")
        if cls.oidc_enabled() and not cls.BASE_URL.startswith(("http://", "https://")):
            errors.append(f"BASE_URL='{cls.BASE_URL}' must start with http:// or https:// when OIDC is enabled")
        if cls.SECRET_KEY == "dev-secret-change-me" and cls.SECURE_COOKIES:
            errors.append(
                "SECRET_KEY is set to the insecure default but SECURE_COOKIES=true indicates "
                "a production deployment. Set SECRET_KEY or SECRET_KEY_FILE before starting."
            )
        if errors:
            raise ValueError("Configuration errors:\n" + "\n".join(f"  - {e}" for e in errors))