class ProviderNotRegisteredError(Exception):
    """ Raised when a provider is requested by ID and not found. """

    def __init__(self, provider_id):
        self.provider_id = provider_id

    def __str__(self):
        msg = "Selection provider with ID '{id}' not found."
        return msg.format(id=self.provider_id)


class IDConflictError(Exception):
    """ Raised when a provider is added and its ID is already registered. """

    def __init__(self, provider_id):
        self.provider_id = provider_id

    def __str__(self):
        msg = "A selection provider with ID '{id}' is already registered."
        return msg.format(id=self.provider_id)


class ListenerNotConnectedError(Exception):
    """ Raised when a listener that was never connected is disconnected. """

    def __init__(self, provider_id, listener):
        self.provider_id = provider_id
        self.listener = listener

    def __str__(self):
        msg = "Selection listener {l} is not connected to provider '{id}'."
        return msg.format(l=self.listener, id=self.provider_id)