from itertools import chain

from image_prediction.info import Info


def flatten_groups_once(groups):
    return chain.from_iterable(groups)


def make_coord_getter(c):
    return {
        "x1": make_getter(Info.X1),
        "x2": make_getter(Info.X2),
        "y1": make_getter(Info.Y1),
        "y2": make_getter(Info.Y2),
    }[c]


def make_getter(key):
    def getter(pair):
        return pair.metadata[key]

    return getter


def make_length_getter(dim):
    return {
        "width": make_getter(Info.WIDTH),
        "height": make_getter(Info.HEIGHT),
    }[dim]