"""Everything the robot layer raises.

The distinctions matter: they say whether the arm moved, whether anything can be
done about it, and whether the answer needs a human first. Taken from the
littlehand robot layer, where they were arrived at against this same controller.
"""


class MotionInterruptedError(Exception):
    """The motion was aborted in flight, by :meth:`ULite6.stop` or a controller fault."""


class RobotUnavailableError(Exception):
    """The command never ran because the arm was not usable.

    A pulled cable, a pressed emergency stop, a latched controller error: what a
    caller must do is the same, and it is never to carry on as if the arm moved.
    Recoverable by :meth:`ULite6.recover`.
    """


class UnreachablePoseError(Exception):
    """The pose was never commanded because the arm cannot hold it.

    Deliberately not a :class:`RobotUnavailableError`: the arm is fine and the
    target is not, so a retry would only ask the same impossible thing and latch
    a joint limit error on the controller.
    """


class ArmNeedsHomingError(RobotUnavailableError):
    """Only a motion of ours can clear this error, so the caller must warn first.

    A joint past its own limit stays past it however often the error is cleared.
    Narrow on purpose: an arm that is stopped rather than stuck — emergency stop
    held, collision to be dragged out of by hand — stays a plain
    :class:`RobotUnavailableError`, because homing it would move an arm somebody
    stopped deliberately.
    """


class EffectorUnsupportedError(Exception):
    """The configured effector is not one this arm can drive."""