from datetime import timedelta

from django.db.models import Count, F
from django.utils import timezone
from ninja import Router
from ninja.errors import HttpError

from apps.accounts.api import require_permission
from apps.workitems.models import WorkItem
from apps.workitems.schemas import WorkItemMetricsOut, WorkItemOut

router = Router(tags=["tasks"])


def serialize_work_item(item: WorkItem) -> dict:
    now = timezone.now()
    if item.status != "active":
        completed_overdue = (
            item.due_at and item.completed_at and item.completed_at > item.due_at
        )
        sla_status = "completed_overdue" if completed_overdue else "completed"
    elif item.due_at and item.due_at <= now:
        sla_status = "overdue"
    elif item.due_at and item.due_at <= now + timedelta(hours=2):
        sla_status = "due_soon"
    else:
        sla_status = "on_track"
    return {
        "public_id": str(item.public_id),
        "task_type": item.task_type,
        "status": item.status,
        "object_type": item.object_type,
        "object_id": item.object_id,
        "ticket_id": item.ticket_id,
        "ticket_no": item.ticket.ticket_no if item.ticket_id else None,
        "title": item.title,
        "description": item.description,
        "payload": item.payload,
        "assignee_id": item.assignee_id,
        "created_at": item.created_at,
        "updated_at": item.updated_at,
        "completed_at": item.completed_at,
        "due_at": item.due_at,
        "sla_status": sla_status,
    }


@router.get("/metrics", response=WorkItemMetricsOut)
def get_work_item_metrics(request):
    require_permission(request, "ticket.view")
    now = timezone.now()
    active = WorkItem.objects.filter(status="active")
    completed = WorkItem.objects.filter(status="completed", completed_at__isnull=False)
    by_task_type = {
        item["task_type"]: item["total"]
        for item in active.values("task_type").annotate(total=Count("id"))
    }
    return {
        "active_count": active.count(),
        "overdue_count": active.filter(due_at__lte=now).count(),
        "due_soon_count": active.filter(
            due_at__gt=now,
            due_at__lte=now + timedelta(hours=2),
        ).count(),
        "completed_within_sla_count": completed.filter(
            completed_at__lte=F("due_at")
        ).count(),
        "completed_overdue_count": completed.filter(
            completed_at__gt=F("due_at")
        ).count(),
        "by_task_type": by_task_type,
    }


@router.get("", response=list[WorkItemOut])
def list_work_items(
    request,
    status: str | None = "active",
    task_type: str | None = None,
    ticket_id: int | None = None,
):
    require_permission(request, "ticket.view")
    queryset = WorkItem.objects.select_related("ticket", "assignee")
    if status:
        queryset = queryset.filter(status=status)
    if task_type:
        queryset = queryset.filter(task_type=task_type)
    if ticket_id:
        queryset = queryset.filter(ticket_id=ticket_id)
    return [serialize_work_item(item) for item in queryset[:200]]


@router.get("/{public_id}", response=WorkItemOut)
def get_work_item(request, public_id: str):
    require_permission(request, "ticket.view")
    item = WorkItem.objects.select_related("ticket", "assignee").filter(
        public_id=public_id
    ).first()
    if item is None:
        raise HttpError(404, "任务不存在")
    return serialize_work_item(item)