"""
ByteAstra backend — MongoDB database setup using PyMongo.
"""
from pymongo import MongoClient
from app.config import get_settings

settings = get_settings()

client = MongoClient(settings.mongo_url)
db = client.get_database("byteastra")


def get_db():
    """FastAPI dependency that provides a MongoDB database session."""
    yield db


def init_db():
    """Configures indexes at startup."""
    
    # Create indexes for high query performance
    db.sessions.create_index("user_id")
    db.sessions.create_index("updated_at")
    db.messages.create_index("session_id")
    db.messages.create_index("created_at")
    db.users.create_index("email", unique=True)