import { db } from '~~/server/lib/db';
import { topicEvents } from '~~/server/utils/events';
import { createTopicSnapshotStream } from '~~/server/utils/topic-snapshot-stream';

export default defineEventHandler(async (event) => {
    await protectRoute(event);

    const topicId = getRouterParam(event, 'topicId')!;
    const userId = event.context.user!.id as string;
    const isSSE = getHeader(event, 'accept')?.includes('text/event-stream') ?? false;
    const readTopic = () => db.query.topics.findFirst({
        where: { id: topicId, userId },
        with: {
            messages: {
                orderBy: { createdAt: 'asc' },
                with: {
                    parts: {
                        orderBy: { createdAt: 'asc' },
                        with: { toolCall: true },
                    },
                    attachments: { with: { file: true } },
                    generation: true,
                },
            },
        },
    });

    if (!isSSE) {
        const topic = await readTopic();
        if (!topic) {
            setResponseStatus(event, 404);
            return { ok: false, error: 'Topic not found' };
        }
        topicEvents.applyLiveText(topicId, topic.messages);
        return topic;
    }

    // Authorize before subscribing; no topic data is exposed before this check.
    const ownedTopic = await db.query.topics.findFirst({
        where: { id: topicId, userId },
        columns: { id: true },
    });
    if (!ownedTopic) {
        setResponseStatus(event, 404);
        return { ok: false, error: 'Topic not found' };
    }

    const subscription = createTopicSnapshotStream(topicId, getQuery(event).snapshot);
    event.node.res.once('close', subscription.close);
    const stream = await subscription.open(readTopic);
    if (!stream.ok) {
        setResponseStatus(event, stream.error === 'read-failed' ? 500 : 404);
        return { ok: false, error: stream.error };
    }
    setHeader(event, 'Content-Type', 'text/event-stream');
    setHeader(event, 'Cache-Control', 'no-cache');
    setHeader(event, 'X-Accel-Buffering', 'no');

    return sendStream(event, stream.data);
});