from django.db.models import Count, F, Q


EVENT_STATUS_LABELS = {
    "draft": "پیش‌نویس",
    "cancelled": "لغو شده",
    "completed": "برگزار شده",
    "in_progress": "در حال برگزاری",
    "registration_closed": "پایان ثبت‌نام",
    "full": "تکمیل ظرفیت",
    "registration_open": "در حال ثبت‌نام",
    "upcoming": "به‌زودی",
}

PUBLIC_EVENT_STATUSES = tuple(key for key in EVENT_STATUS_LABELS if key != "draft")


def active_registration_count_annotation(*, now, relation="registrations"):
    return Count(
        relation,
        filter=Q(**{f"{relation}__is_deleted": False})
        & (
            Q(**{f"{relation}__status__in": ["confirmed", "attended"]})
            | Q(
                **{
                    f"{relation}__status": "pending",
                    f"{relation}__checkout_expires_at__gt": now,
                }
            )
        ),
        distinct=True,
    )


def event_status_filter(status, *, now, prefix="", count_field="browse_registration_count"):
    """Return a queryset condition for a derived event status.

    The caller should restrict the queryset to published events and annotate the
    active registration count using ``count_field`` before applying this filter.
    """
    def field(name):
        return f"{prefix}{name}"
    count = F(count_field)
    before_event_start = Q(**{f"{field('start_time')}__gt": now})
    deadline_open = Q(**{f"{field('registration_end_date')}__isnull": True}) | Q(
        **{f"{field('registration_end_date')}__gt": now}
    )

    if status == "cancelled":
        return Q(**{field("is_cancelled"): True})
    if status == "completed":
        return Q(**{f"{field('end_time')}__lte": now}) & Q(**{field("is_cancelled"): False})
    if status == "in_progress":
        return (
            Q(**{f"{field('start_time')}__lte": now})
            & Q(**{f"{field('end_time')}__gt": now})
            & Q(**{field("is_cancelled"): False})
        )
    if status == "registration_closed":
        return (
            before_event_start
            & Q(**{f"{field('registration_end_date')}__lte": now})
            & Q(**{field("is_cancelled"): False})
        )
    if status == "full":
        return (
            before_event_start
            & deadline_open
            & Q(**{f"{field('capacity')}__isnull": False})
            & Q(**{f"{field('capacity')}__lte": count})
            & Q(**{field("is_cancelled"): False})
        )
    if status == "registration_open":
        registration_started = Q(**{f"{field('registration_start_date')}__isnull": True}) | Q(
            **{f"{field('registration_start_date')}__lte": now}
        )
        capacity_available = Q(**{f"{field('capacity')}__isnull": True}) | Q(
            **{f"{field('capacity')}__gt": count}
        )
        return (
            before_event_start
            & registration_started
            & deadline_open
            & capacity_available
            & Q(**{field("is_cancelled"): False})
        )
    if status == "upcoming":
        registration_not_started = Q(**{f"{field('registration_start_date')}__gt": now})
        capacity_available = Q(**{f"{field('capacity')}__isnull": True}) | Q(
            **{f"{field('capacity')}__gt": count}
        )
        return (
            before_event_start
            & registration_not_started
            & deadline_open
            & capacity_available
            & Q(**{field("is_cancelled"): False})
        )
    raise ValueError(f"Unsupported event status: {status}")