"""Playback helpers — selecting and cycling through frames by label."""


def frames_with_label(assignments: dict, label: str) -> list:
    """Sorted frame indices assigned the given label."""
    return sorted(i for i, lbl in assignments.items() if lbl == label)


def next_in_cycle(indices: list, current: int, delta: int) -> int:
    """Next index in `indices` after `current`, wrapping around.

    If `current` isn't in the set, returns the first index.
    """
    if current in indices:
        pos = indices.index(current)
        return indices[(pos + delta) % len(indices)]
    return indices[0]