from django.utils import timezone

from apps.audit.models import OperationAuditLog
from apps.tickets.models import Ticket, TicketEvent


class TicketStatusError(ValueError):
    pass


ALLOWED_TRANSITIONS: dict[str, set[str]] = {
    "pending_info": {"pending", "closed"},
    "pending": {"in_progress", "closed"},
    "in_progress": {"pending_confirm"},
    "pending_confirm": {"resolved", "in_progress", "closed"},
    "resolved": {"closed"},
    "closed": set(),
}


def validate_status_transition(from_status: str, to_status: str) -> None:
    if to_status not in ALLOWED_TRANSITIONS.get(from_status, set()):
        raise TicketStatusError(f"Invalid ticket status transition: {from_status} -> {to_status}")


def transition_ticket(ticket: Ticket, to_status: str, remark: str = "", operator=None) -> Ticket:
    from_status = ticket.status
    validate_status_transition(from_status, to_status)
    ticket.status = to_status
    if to_status == "resolved":
        ticket.resolved_at = timezone.now()
    if to_status == "closed":
        ticket.closed_at = timezone.now()
    ticket.save(update_fields=["status", "resolved_at", "closed_at", "updated_at"])
    TicketEvent.objects.create(
        ticket=ticket,
        event_type="status_change",
        from_value={"status": from_status},
        to_value={"status": to_status},
        operator=operator,
        remark=remark,
    )
    OperationAuditLog.objects.create(
        user=operator,
        module="tickets",
        action="status_transition",
        target_type="ticket",
        target_id=str(ticket.id),
        result="success",
        request_snapshot={"from": from_status, "to": to_status, "remark": remark},
    )
    return ticket