import dataclasses
import datetime
from collections.abc import Sequence

HIDDEN_LABEL_CATEGORY = '__'

@dataclasses.dataclass(frozen=True, order=True)
class Label:
    category: str
    label: str

    def __post_init__(self):
        assert self.category is not None
        assert ':' not in self.category
        assert self.label is not None

@dataclasses.dataclass(frozen=True, order=True)
class ActivitySample:
    labels: Sequence[Label]
    start_at: datetime.datetime | None
    end_at: datetime.datetime | None


@dataclasses.dataclass(frozen=True, order=True)
class RealizedActivitySample(ActivitySample):
    start_at: datetime.datetime
    end_at: datetime.datetime