from typing import List
import uuid

from django.utils import timezone

from bookings.models import Booking, Ticket


def _generate_ticket_id(booking: Booking) -> str:
    """
    Generate a ticket_id based on the event name and a random UUID segment.

    Pattern: <EVT><RANDOM_HEX>
    - EVT: first 3 characters of event name (uppercase), or 'EVT' fallback
    - RANDOM_HEX: first 10 chars of uuid4 hex (uppercase)
    """
    event = getattr(booking.ticket_meta, "event", None)
    if event and getattr(event, "name", None):
        prefix = (event.name or "EVT")[:3].upper()
    else:
        prefix = "EVT"

    return prefix + uuid.uuid4().hex[:10].upper()


def generate_tickets_for_booking(booking: Booking) -> List[Ticket]:
    """
    Generate Ticket instances for a given Booking based on its quantity.

    This function does NOT perform any payment or business-rule validation.
    It simply creates one Ticket per quantity on the booking.

    Args:
        booking: Booking instance for which tickets should be generated.

    Returns:
        List[Ticket]: List of created Ticket instances.
    """
    if not isinstance(booking, Booking):
        raise TypeError("booking must be a Booking instance")

    if booking.quantity <= 0:
        return []

    tickets: List[Ticket] = []
    for _ in range(booking.quantity):
        tickets.append(
            Ticket(
                booking=booking,
                ticket_id=_generate_ticket_id(booking),
                is_checked_in=False,
                checked_in_date_time=None,
            )
        )

    # Bulk create for efficiency
    Ticket.objects.bulk_create(tickets)

    # Refresh from DB to ensure we have primary keys and any defaults
    return list[Ticket](Ticket.objects.filter(booking=booking).order_by("id"))