"""Database connection utilities for Home Assistant PostgreSQL database."""

import os
from functools import lru_cache

from dotenv import load_dotenv
from sqlalchemy import create_engine, text
from sqlalchemy.orm import sessionmaker

# Load environment variables from .env file
load_dotenv()


@lru_cache(maxsize=1)
def _get_engine(echo: bool = False):
    """Create and cache the database engine (singleton)."""
    required_vars = [
        "POSTGRES_HOST",
        "POSTGRES_PORT",
        "POSTGRES_DB",
        "POSTGRES_USER",
        "POSTGRES_PASSWORD",
    ]
    missing_vars = [var for var in required_vars if not os.getenv(var)]

    if missing_vars:
        raise ValueError(f"Missing required environment variables: {', '.join(missing_vars)}")

    connection_string = (
        f"postgresql://{os.getenv('POSTGRES_USER')}:{os.getenv('POSTGRES_PASSWORD')}"
        f"@{os.getenv('POSTGRES_HOST')}:{os.getenv('POSTGRES_PORT')}/{os.getenv('POSTGRES_DB')}"
    )

    return create_engine(connection_string, echo=echo)


def get_db_session(echo: bool = False) -> sessionmaker:
    """
    Create a SQLAlchemy sessionmaker for the Home Assistant PostgreSQL database.

    Args:
        echo: If True, log all SQL statements (default: False)

    Returns:
        sessionmaker: Database session maker object

    Raises:
        ValueError: If required environment variables are not set
    """

    # Create the SQLAlchemy engine
    engine = _get_engine(echo=echo)

    # Create a session maker
    session = sessionmaker(bind=engine)

    # Test connection to database
    with session.begin() as s:
        s.execute(text("SELECT 1"))

    return session