"""
db.py — MongoDB Atlas connection with mongomock fallback.
If MONGO_URI is not set or the connection fails, the app runs on an
in-memory mock store so development works without any database.
"""

import os
import logging
from dotenv import load_dotenv

load_dotenv()

logger = logging.getLogger(__name__)

MONGO_URI = os.getenv("MONGO_URI") or os.getenv("MONGODB_URI") or ""
DB_NAME = "squad_qa"

_client = None
_db = None
_using_mock = False


def _connect_atlas():
    """Attempt to connect to MongoDB Atlas (or local Mongo)."""
    global _client, _db, _using_mock
    try:
        from pymongo import MongoClient
        from pymongo.errors import ConnectionFailure, ConfigurationError, ServerSelectionTimeoutError

        if not MONGO_URI or "username:password" in MONGO_URI:
            raise ValueError("MONGO_URI not configured — falling back to mock.")

        _client = MongoClient(MONGO_URI, serverSelectionTimeoutMS=5000, tls=True, tlsAllowInvalidCertificates=True)
        # Trigger actual connection check
        _client.admin.command("ping")
        _db = _client[DB_NAME]
        _using_mock = False
        logger.info("[DB] Connected to MongoDB Atlas successfully.")
    except Exception as exc:
        logger.warning(f"[DB] MongoDB connection failed: {exc}")
        logger.warning("[DB] Falling back to in-memory mongomock.")
        _connect_mock()


def _connect_mock():
    """Fall back to mongomock (in-memory, no persistence)."""
    global _client, _db, _using_mock
    try:
        import mongomock
        _client = mongomock.MongoClient()
        _db = _client[DB_NAME]
        _using_mock = True
        logger.warning("[DB] Running on mongomock — data will NOT persist across restarts.")
    except ImportError:
        logger.error("[DB] mongomock not installed. Database unavailable.")
        _db = None


def get_db():
    """Return the active database handle (Atlas or mock)."""
    global _db
    if _db is None:
        _connect_atlas()
    return _db


def is_using_mock():
    return _using_mock


# Initialise on import
_connect_atlas()

# Convenience collection accessors
def users_col():
    return get_db()["users"]

def chats_col():
    return get_db()["chats"]

def settings_col():
    return get_db()["settings"]