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):
    registrations_last_month = EventRegistration.objects.filter(
        user_id=user.id,
        event__date__gt=date.today() - timedelta(days=30),
        event__date__lte=date.today(),
        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:
    """
    out = []

    # Get all events of tomorrow
    events = Event.objects.filter(date=date.today() + timedelta(days=1))

    out.append(f"{len(events) if events else 'Geen'} event(s)")

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

    out.append(f"{len(registrations) if registrations else 'Geen'} registratie(s)")
    out.append("")

    # Relevant users
    users = [r.user for r in registrations if r.state == EventRegistration.INTERESTED]
    scores = list(map(calc_score, users))
    queue = sorted(list(zip(users, scores)), key=lambda tup: tup[1])
    out.append("Prioriteiten: " + ", ".join(f"{u.username} ({s})" for u, s in queue))
    out.append("")

    for event in events:
        registrations = [r for r in registrations if r.event == event]

        already_admitted_regs = [r for r in registrations if r.state == EventRegistration.ADMITTED]
        left = max(event.capacity - sum(1 for r in already_admitted_regs), 0)

        moment_str = Event.TIME_SLOTS[event.time]
        out.append(f"• Event: {event.date}, {moment_str}. Vrije plaatsen: {left}/{event.capacity}")
        for reg in already_admitted_regs:
            out.append(f"    = {reg.user.username}")

        interested_users = {r.user for r in registrations
                            if r.state == EventRegistration.INTERESTED}
        user_queue = list(filter(lambda element: element[0] in interested_users, queue))

        for user in user_queue[0:left]:
            out.append(f"    + {user[0].username}")
            r = EventRegistration.objects.get(
                event_id=event.id,
                user_id=user[0].id
            )
            r.state = EventRegistration.ADMITTED
            r.save()
            left -= 1

        out.append(f"  → Vrije plaatsen: {left}/{event.capacity}")

    return "\n".join(out)