"""
Database engine + session management (SQLite for development, per blueprint;
swap DATABASE_URL in config.py for PostgreSQL/MySQL later without touching
any router or service code).
"""

from sqlalchemy import create_engine
from sqlalchemy.orm import sessionmaker, declarative_base

from app.config import DATABASE_URL

engine = create_engine(
    DATABASE_URL,
    connect_args={"check_same_thread": False},  # needed for SQLite + FastAPI threads
)

SessionLocal = sessionmaker(autocommit=False, autoflush=False, bind=engine)

Base = declarative_base()


def get_db():
    """FastAPI dependency — yields a DB session and always closes it."""
    db = SessionLocal()
    try:
        yield db
    finally:
        db.close()


def init_db():
    """Create all tables. Called once on app startup."""
    from app import models_db  # noqa: F401 — ensure models are registered
    Base.metadata.create_all(bind=engine)