import uuid


class DuplicateInstanceError(Exception):
  def __init__(self, instance):
    self.instance = instance


class BaseInstance:
  """
  Base class for all instances (manageable by InstancesManager)
  """
  
  def __init__(self, session: dict, _id: str):
    self._session = session
    self._id = _id
    InstancesManager.register(session, self)
  
  def get_id(self):
    return self._id
  
  def get_session(self):
    return self._session


class SingleInstance(BaseInstance):
  """
  Base class for instances that can only have one instance at a time.
  """
  
  def __init__(self, session: dict, prefix: str):
    super().__init__(session, prefix)
    self._instance = None


class MultipleInstance(BaseInstance):
  """
  Base class for instances that can have multiple instances at a time.
  """
  
  def __init__(self, session: dict, prefix: str):
    super().__init__(session, f"{prefix}-{str(uuid.uuid4())}")
    self._instance = None


class InstancesManager:
  instances = {}
  
  @staticmethod
  def register(session: dict, instance: BaseInstance):
    """
    Register an instance in the manager, so that it can be retrieved later.
    :param session:
    :param instance:
    :return:
    """
    key = (InstancesManager._get_session_id(session), instance.get_id())
    
    if isinstance(instance, SingleInstance) and key in InstancesManager.instances:
      raise DuplicateInstanceError(instance)
    
    InstancesManager.instances[key] = instance
    return instance
  
  @staticmethod
  def get(session: dict, instance_id: str, instance_type: type = None, *args, **kwargs):
    """
    Get or create an instance of the given type (from its id)
    :param session:
    :param instance_id:
    :param instance_type:
    :param args:
    :param kwargs:
    :return:
    """
    try:
      key = (InstancesManager._get_session_id(session), instance_id)
      
      return InstancesManager.instances[key]
    except KeyError:
      return instance_type(session, *args, **kwargs)  # it will be automatically registered
  
  @staticmethod
  def _get_session_id(session):
    if not session:
      return "** NOT LOGGED IN **"
    if "user_info" not in session:
      return "** UNKNOWN USER **"
    return session["user_info"].get("id", "** INVALID SESSION **")