relative-history-date.py

from datetime import datetime


def relative_history_date(history_datetime):
    """Format history datetime to relative representation.

    Parameters
    ----------
    history_datetime : datetime

    Returns
    -------
    str
        A string represents history datetime in a specific context.
    """
    assert type(history_datetime) == datetime
    current_datetime = datetime.now()
    assert history_datetime <= current_datetime

    delta = current_datetime - history_datetime
    # two adjacent days
    if delta.days < 2 and current_datetime.day - history_datetime.day < 2:
        if history_datetime.day == current_datetime.day:
            if delta.seconds < 60:
                return f'{delta.seconds} seconds ago'
            elif delta.seconds < 3600:
                return f'{delta.seconds // 60} minutes ago'
            else:
                return f'{history_datetime:%H:%M:%S} at today'
        else:
            return f'{history_datetime:%H:%M:%S} at yesterday'
    # In the same week
    elif delta.days < 7 and history_datetime.weekday() <= current_datetime.weekday():
        return f'{history_datetime:%H:%M:%S} at {history_datetime:%A}'
    elif history_datetime.year < current_datetime.year:
        return f'{history_datetime:%H:%M:%S} at {history_datetime:%B %d}, {history_datetime:%Y}'
    else:
        return f'{history_datetime:%H:%M:%S} at {history_datetime:%B %d}'


def test_relative_history_date():
    from datetime import timedelta

    current_datetime = datetime.now()
    history_datetime = current_datetime - timedelta(seconds=1)
    assert relative_history_date(history_datetime) == '1 seconds ago'
    history_datetime = current_datetime - timedelta(seconds=60)
    assert relative_history_date(history_datetime) == '1 minutes ago'
    history_datetime = current_datetime - timedelta(seconds=3600)
    assert relative_history_date(history_datetime) == f'{history_datetime:%H:%M:%S} at today'
    date = current_datetime.date()
    history_datetime = datetime(date.year, date.month, date.day)
    assert relative_history_date(history_datetime) == '00:00:00 at today'
    history_datetime = datetime(
        date.year, date.month, date.day) - timedelta(seconds=1)
    assert relative_history_date(history_datetime) == '23:59:59 at yesterday'
    history_datetime = datetime(
        date.year, date.month, date.day) - timedelta(days=1, seconds=1)
    if current_datetime.weekday() == 0:
        assert relative_history_date(history_datetime) == f'23:59:59 at {history_datetime:%B %d}'
    else:
        assert relative_history_date(history_datetime) == f'23:59:59 at {history_datetime:%A}'
    history_datetime = datetime(date.year - 1, 1, 1)
    assert relative_history_date(history_datetime) == f'00:00:00 at January 01, {history_datetime:%Y}'