Converts a date string to a human readable date string.

how_long_ago.py

"""
This program converts a date string to a human readable date string.
Example: `2022-11-5 7:00:10`  --> 2 months ago
"""
import datetime


def calculate_time_difference(date_input):
    now = datetime.datetime.now()
    return now - date_input


def convert_time_difference_to_string(time_difference):
    seconds = time_difference.total_seconds()
    # Calculate the approximate number of seconds in each period and set variable.
    time_units = [
        (365.25 * 24 * 60 * 60, 'year'),
        (30 * 24 * 60 * 60, 'month'),
        (24 * 60 * 60, 'day'),
        (60 * 60, 'hour'),
        (60, 'minute'),
        (1, 'second')
    ]
    # Remove conditional if you want `3` seconds ago` instead of `Just now`.
    if seconds < 60:
        return "Just now"

    for value, unit in time_units:
        if seconds >= value:
            num_units = int(seconds // value)
            time_string = f'{num_units} {unit}'
            if num_units > 1:
                time_string += 's'
            break
    else:
        time_string = '0 seconds'
    time_string += ' ago'
    return time_string


def get_how_long_ago(date_input):
    try:
        # Convert the date_string to a datetime object.
        date = datetime.datetime.strptime(date_input, '%Y-%m-%d %H:%M:%S')
    except ValueError:
        return '! Invalid date format.'

    now = datetime.datetime.now()
    if date > now:
        return '! Date is in the future.'

    time_difference = calculate_time_difference(date)
    return convert_time_difference_to_string(time_difference)


def main():
    line_width = 60
    separator = '='
    print(f"{' [ Generated From now() ] '.center(line_width, separator)}")

    for i in range(10):
        generated_date_in_past = datetime.datetime.now(
        ) + datetime.timedelta(seconds=-(2**(i+1))**3)
        generated_date_in_past = generated_date_in_past.strftime(
            "%Y-%m-%d %H:%M:%S")
        print('- ', get_how_long_ago(generated_date_in_past))

    print(f"{' [ Static Examples ] '.center(line_width, separator)}")
    print(get_how_long_ago('1954-05-05 9:33:10'))
    print(get_how_long_ago('2022-11-5 7:00:10'))
    print(get_how_long_ago('2023-01-1 11:13:37'))
    print(get_how_long_ago('2023-01-9 12:22:50'))
    print(get_how_long_ago('2033-09-06 22:45:50'))
    print(f"{' [ Illegal Examples ] '.center(line_width, separator)}")
    print(get_how_long_ago('2023-01-32 19:33:30'))
    print(get_how_long_ago('2018-02-29 19:33:30'))
    print(get_how_long_ago('2018-01-01 25:00:00'))
    print(get_how_long_ago('2018-01-01 19:00:70'))
    print(f"{' [] '.center(line_width, separator)}")


if __name__ == '__main__':
    main()