"""Configuration helpers for connecting to the MSSQL sandbox."""

from __future__ import annotations

import os
from dataclasses import dataclass


@dataclass(frozen=True)
class DbSettings:
    """Environment-driven connection settings for SQL Server.

    Required variables:
    - DB_SERVER (e.g., 
    - DB_DATABASE (e.g., "SugarScale_Lasuca")
    - DB_USERNAME (database login)
    - DB_PASSWORD (database password)

    Optional overrides:
    - DB_DRIVER (defaults to "$env")
    - DB_ENCRYPT ("true" to enable TLS)
    - DB_TRUST_CERT ("true" to trust the server certificate)
    """

    server: str
    database: str
    username: str
    password: str
    driver: str = "ODBC Driver 18 for SQL Server"
    encrypt: bool = True
    trust_server_certificate: bool = True

    @classmethod
    def from_env(cls) -> "DbSettings":
        missing: list[str] = []
        server = os.getenv("DB_SERVER")
        if not server:
            missing.append("DB_SERVER")
        database = os.getenv("DB_DATABASE")
        if not database:
            missing.append("DB_DATABASE")
        username = os.getenv("DB_USERNAME")
        if not username:
            missing.append("DB_USERNAME")
        password = os.getenv("DB_PASSWORD")
        if not password:
            missing.append("DB_PASSWORD")

        if missing:
            raise RuntimeError(
                "Missing required environment variables: " + ", ".join(missing)
            )

        driver = os.getenv("DB_DRIVER", "ODBC Driver 18 for SQL Server")
        encrypt = os.getenv("DB_ENCRYPT", "true").lower() == "true"
        trust = os.getenv("DB_TRUST_CERT", "true").lower() == "true"

        return cls(
            server=server,
            database=database,
            username=username,
            password=password,
            driver=driver,
            encrypt=encrypt,
            trust_server_certificate=trust,
        )

    def connection_string(self) -> str:
        parts = [
            f"DRIVER={{{self.driver}}}",
            f"SERVER={self.server}",
            f"DATABASE={self.database}",
            f"UID={self.username}",
            f"PWD={self.password}",
        ]
        if self.encrypt:
            parts.append("Encrypt=yes")
        if self.trust_server_certificate:
            parts.append("TrustServerCertificate=yes")
        parts.append("MARS_Connection=yes")
        return ";".join(parts)