from sqlalchemy import create_engine, event
from sqlalchemy.orm import sessionmaker, DeclarativeBase
from config import get_settings

settings = get_settings()

_is_sqlite = "sqlite" in settings.DATABASE_URL

engine = create_engine(
    settings.DATABASE_URL,
    connect_args={"check_same_thread": False} if _is_sqlite else {},
    echo=settings.DEBUG,
)

# SQLite concurrency hardening: enable WAL mode + busy_timeout on every connection.
# WAL allows concurrent readers alongside a single writer, eliminating most
# "database is locked" errors under FastAPI's threaded request handling.
if _is_sqlite:
    @event.listens_for(engine, "connect")
    def _set_sqlite_pragma(dbapi_conn, conn_record):
        cur = dbapi_conn.cursor()
        cur.execute("PRAGMA journal_mode=WAL")
        cur.execute("PRAGMA synchronous=NORMAL")
        cur.execute("PRAGMA busy_timeout=10000")
        cur.execute("PRAGMA foreign_keys=ON")
        cur.close()

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


class Base(DeclarativeBase):
    pass


def get_db():
    db = SessionLocal()
    try:
        yield db
    finally:
        db.close()