"""
Session Manager - Singleton pattern for managing authenticated user session
"""
from typing import Optional, Dict, Any


class SessionManager:
    """
    Singleton session manager to maintain authenticated user state
    throughout the application lifecycle.
    """

    _instance = None

    def __new__(cls):
        """Implement singleton pattern"""
        if cls._instance is None:
            cls._instance = super(SessionManager, cls).__new__(cls)
            cls._instance._initialized = False
        return cls._instance

    def __init__(self):
        """Initialize the session manager (only once)"""
        if self._initialized:
            return

        self._current_user = None  # {username, user_type}
        self._initialized = True

    @classmethod
    def get_instance(cls) -> 'SessionManager':
        """
        Get the singleton instance of SessionManager

        Returns:
            The singleton SessionManager instance
        """
        if cls._instance is None:
            cls._instance = cls()
        return cls._instance

    def login(self, username: str, password: str) -> bool:
        """
        Authenticate and login a user

        Args:
            username: The username to authenticate
            password: The password to verify

        Returns:
            True if login successful, False otherwise
        """
        from db.bip_users_dao import BIPUsersDAO

        dao = BIPUsersDAO()
        user_info = dao.authenticate(username, password)

        if user_info:
            self._current_user = {
                'username': user_info['username'],
                'user_type': user_info['user_type']
            }
            return True
        return False

    def login_by_computer_name(self) -> bool:
        """
        Attempt silent login using computer name

        Returns:
            True if login successful, False otherwise
        """
        import socket
        from db.bip_users_dao import BIPUsersDAO

        computer_name = socket.gethostname()
        dao = BIPUsersDAO()
        user_info = dao.authenticate_by_computer_name(computer_name)

        if user_info:
            self._current_user = {
                'username': user_info['username'],
                'user_type': user_info['user_type']
            }
            return True
        return False

    def logout(self):
        """Logout the current user and clear session"""
        self._current_user = None

    def is_authenticated(self) -> bool:
        """
        Check if a user is currently authenticated

        Returns:
            True if user is logged in, False otherwise
        """
        return self._current_user is not None

    def is_admin(self) -> bool:
        """
        Check if the current user is an admin

        Returns:
            True if current user is admin, False otherwise
        """
        if not self._current_user:
            return False
        return self._current_user.get('user_type') == 'Admin'

    def is_guest(self) -> bool:
        """
        Check if the current user is a guest

        Returns:
            True if current user is guest, False otherwise
        """
        if not self._current_user:
            return False
        return self._current_user.get('user_type') == 'Guest'

    def get_username(self) -> Optional[str]:
        """
        Get the current username

        Returns:
            Current username if authenticated, None otherwise
        """
        if not self._current_user:
            return None
        return self._current_user.get('username')

    def get_user_type(self) -> Optional[str]:
        """
        Get the current user type

        Returns:
            Current user type if authenticated, None otherwise
        """
        if not self._current_user:
            return None
        return self._current_user.get('user_type')

    def get_user_info(self) -> Optional[dict]:
        """
        Get all current user information

        Returns:
            Dict with username and user_type if authenticated, None otherwise
        """
        return self._current_user

    def switch_user(self, user_info: Dict[str, Any]) -> bool:
        """
        Switch to a different user (Admin only feature)

        This allows an Admin user to operate as a different user
        with that user's permissions.

        Args:
            user_info: Dict with {id, username, user_type}

        Returns:
            True if switch successful
        """
        if not self._current_user:
            return False

        # Store original admin user for reference
        if not hasattr(self, '_original_admin_user'):
            self._original_admin_user = self._current_user.copy()

        self._current_user = {
            'username': user_info['username'],
            'user_type': user_info['user_type']
        }
        return True

    def get_original_admin(self) -> Optional[Dict[str, Any]]:
        """
        Get the original Admin user before any user switch

        Returns:
            Original admin user dict if a switch occurred, None otherwise
        """
        return getattr(self, '_original_admin_user', None)