backend/app/db/db_connector.py

from sqlalchemy import create_engine
from sqlalchemy.engine import Engine
from sqlalchemy.orm import sessionmaker
from app.services.utility import UtilityClass
import sqlite3
from pathlib import Path
import os
from dotenv import load_dotenv
load_dotenv()

# Path to SQLite DB file, configurable via environment variable or .env
print("DB_PATH from env:", os.getenv("DB_PATH"))
DB_PATH = os.getenv("DB_PATH")
# DB_PATH = UtilityClass.download_sqlite_db_from_dropbox(os.getenv("DROPBOX_TOKEN"), os.getenv("DROPBOX_DB_PATH"))
if not DB_PATH:
    BASE_DIR = os.path.dirname(os.path.abspath(__file__))
    DB_PATH = os.path.join(BASE_DIR, "Banking.db")

DATABASE_URL = f"sqlite:///{DB_PATH}"

def get_connection():
    db_path = DB_PATH
    # Only allow connection if DB file exists
    if not os.path.isfile(db_path):
        raise FileNotFoundError(f"Database file not found at {db_path}. Set DB_PATH env variable or .env to the correct location.")
    try:
        # Remove timeout restriction to allow long-running queries
        # Complex AI-generated queries may take time and should not be interrupted
        conn = sqlite3.connect(db_path, check_same_thread=False)
        conn.row_factory = sqlite3.Row  # access columns by name
        return conn
    except sqlite3.OperationalError as e:
        raise Exception(f"Error connecting to DB at {db_path}: {e}")

# Create engine with no timeout restrictions for complex queries
engine = create_engine(
    DATABASE_URL,
    connect_args={
        "check_same_thread": False,  # Needed for SQLite threading
        "timeout": 0  # No timeout - wait indefinitely for query completion
    },
    pool_timeout=None,  # No pool timeout
    pool_recycle=-1    # No connection recycling timeout
)

# Session factory
SessionLocal = sessionmaker(autocommit=False, autoflush=False, bind=engine)

def get_db_engine():
    """Return SQLAlchemy engine (used by LangChain SQLDatabase)."""
    return engine


def get_db():
    """Provide DB session for queries."""
    db = SessionLocal()
    try:
        yield db
    finally:
        db.close()