kers/events/tasks.py

from datetime import date, timedelta
from typing import List

from KeRS.celery import app
from events.models import Event, EventRegistration
from users.models import CustomUser


def calc_score(user: CustomUser, for_date):
    registrations_last_month = EventRegistration.objects.filter(
        user_id=user.id,
        event__date__gt=for_date - timedelta(days=30),
        event__date__lte=for_date,
        state=EventRegistration.ADMITTED
    )

    score = 0
    for r in registrations_last_month:
        days_ago = (date.today() - r.event.date.date()).days
        score += 1 / (days_ago + 1)

    return score


@app.task(bind=True)
def assign_reservations(self):
    """
    Check if there are any events tomorrow.
    If so, calculate the current score for every interested user and assign the ones with the lowest scores.
    :param self:
    :return:
    """
    print("Assigning reservations")
    print("======================")
    # Get all events of tomorrow
    events = Event.objects.all().filter(date__date=date.today() + timedelta(days=1))

    # Reservations
    registrations: List[EventRegistration] = EventRegistration.objects.filter(
        event_id__in=map(lambda event: event.id, events),
        state=EventRegistration.INTERESTED)

    if len(registrations) == 0:
        print("NO REGISTRATIONS?")

    # Relevant users
    users = set(map(lambda r: r.user, registrations))
    scores = list(map(calc_score, users))
    queue = sorted(list(zip(users, scores)), key=lambda tup: tup[1])
    print(f"Scores: {scores}")
    print(f"Queue: {queue}")

    for event in events:
        print(f"EVENT: {event.date} - {event.capacity}")
        event_registrations = list(filter(lambda r: r.event == event, registrations))
        event_users = set(map(lambda r: r.user, event_registrations))
        event_queue = list(filter(lambda element: element[0] in event_users, queue))

        for user in event_queue[0:event.capacity]:
            print(f"Selected {user[0]}")
            r = EventRegistration.objects.get(
                event_id=event.id,
                user_id=user[0].id
            )
            r.state = EventRegistration.ADMITTED
            r.save()