feat: add ticket domain models

backend/apps/tickets/services.py

@@ -0,0 +1,52 @@
+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", "resolved", "closed"},
+    "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