import json
import time

from django.conf import settings
from django.http import StreamingHttpResponse
from ninja import Router
from ninja.errors import HttpError

from apps.accounts.api import require_permission
from apps.tickets.models import TicketAutomationRun

router = Router(tags=["ticket-automation-runs"])


def _cursor(request, after: int | None) -> int:
    raw = request.headers.get("Last-Event-ID") or after or 0
    try:
        return max(int(raw), 0)
    except (TypeError, ValueError) as error:
        raise HttpError(400, "事件游标无效") from error


def _format_event(event) -> str:
    payload = {
        "sequence": event.sequence,
        "event_type": event.event_type,
        "payload": event.payload,
        "created_at": event.created_at.isoformat(),
    }
    return (
        f"id: {event.sequence}\n"
        f"event: {event.event_type}\n"
        f"data: {json.dumps(payload, ensure_ascii=False)}\n\n"
    )


@router.get("/{public_id}/events")
def stream_ticket_automation_events(request, public_id: str, after: int | None = None):
    require_permission(request, "ticket.view")
    run = TicketAutomationRun.objects.filter(public_id=public_id).first()
    if run is None:
        raise HttpError(404, "工单自动化运行不存在")
    cursor = _cursor(request, after)
    terminal = {"completed", "failed", "cancelled"}
    max_seconds = getattr(settings, "AGENT_RUN_SSE_MAX_SECONDS", 60)

    def event_stream():
        current = cursor
        started = time.monotonic()
        heartbeat = started
        while time.monotonic() - started < max_seconds:
            events = list(run.events.filter(sequence__gt=current)[:100])
            for event in events:
                current = event.sequence
                yield _format_event(event)
            if events and events[-1].event_type in terminal:
                return
            now = time.monotonic()
            if now - heartbeat >= 15:
                yield ": keep-alive\n\n"
                heartbeat = now
            time.sleep(0.5)

    response = StreamingHttpResponse(event_stream(), content_type="text/event-stream")
    response["Cache-Control"] = "no-cache"
    response["X-Accel-Buffering"] = "no"
    return response