from bu4.linking.afterlinking import AfterLinking
from bu4.linking.alal import ALAL
from bu4.parsing.linked import LinkingState, Linked
from bu4.linking.linkingfinished import LinkingFinished
from bu4.linking.linkingparsed import LinkingParsed


def _afterlinking_iteration(state: AfterLinking) -> LinkingState:
    if isinstance(state.state, LinkingFinished):
        state = state.target.given(state.state.linked)
    elif isinstance(state.state, AfterLinking):
        state.state, state.target = state.state.state, ALAL(state.state.target, state.target)
    elif isinstance(state.state, LinkingParsed):
        state.state = state.state.parsed.link(state.state.promise).link()
    else:
        raise TypeError
    return state


def prepare(linked: Linked) -> Linked:
    state = linked.link()
    while True:
        if isinstance(state, LinkingFinished):
            return state.linked
        elif isinstance(state, AfterLinking):
            state = _afterlinking_iteration(state)
        else:
            raise TypeError