next-ai-draw-io/app/api/log-feedback/route.ts

import { getLangfuseClient } from '@/lib/langfuse';
import { randomUUID } from 'crypto';
import { z } from 'zod';

const feedbackSchema = z.object({
  messageId: z.string().min(1).max(200),
  feedback: z.enum(['good', 'bad']),
  sessionId: z.string().min(1).max(200).optional(),
});

export async function POST(req: Request) {
  const langfuse = getLangfuseClient();
  if (!langfuse) {
    return Response.json({ success: true, logged: false });
  }

  // Validate input
  let data;
  try {
    data = feedbackSchema.parse(await req.json());
  } catch {
    return Response.json({ success: false, error: 'Invalid input' }, { status: 400 });
  }

  const { messageId, feedback, sessionId } = data;

  // Get user IP for tracking
  const forwardedFor = req.headers.get('x-forwarded-for');
  const userId = forwardedFor?.split(',')[0]?.trim() || 'anonymous';

  try {
    // Find the most recent chat trace for this session to attach the score to
    const tracesResponse = await langfuse.api.trace.list({
      sessionId,
      limit: 1,
    });

    const traces = tracesResponse.data || [];
    const latestTrace = traces[0];

    if (!latestTrace) {
      // No trace found for this session - create a standalone feedback trace
      const traceId = randomUUID();
      const timestamp = new Date().toISOString();

      await langfuse.api.ingestion.batch({
        batch: [
          {
            type: 'trace-create',
            id: randomUUID(),
            timestamp,
            body: {
              id: traceId,
              name: 'user-feedback',
              sessionId,
              userId,
              input: { messageId, feedback },
              metadata: { source: 'feedback-button', note: 'standalone - no chat trace found' },
              timestamp,
            },
          },
          {
            type: 'score-create',
            id: randomUUID(),
            timestamp,
            body: {
              id: randomUUID(),
              traceId,
              name: 'user-feedback',
              value: feedback === 'good' ? 1 : 0,
              comment: `User gave ${feedback} feedback`,
            },
          },
        ],
      });
    } else {
      // Attach score to the existing chat trace
      const timestamp = new Date().toISOString();

      await langfuse.api.ingestion.batch({
        batch: [
          {
            type: 'score-create',
            id: randomUUID(),
            timestamp,
            body: {
              id: randomUUID(),
              traceId: latestTrace.id,
              name: 'user-feedback',
              value: feedback === 'good' ? 1 : 0,
              comment: `User gave ${feedback} feedback`,
            },
          },
        ],
      });
    }

    return Response.json({ success: true, logged: true });
  } catch (error) {
    console.error('Langfuse feedback error:', error);
    return Response.json({ success: false, error: 'Failed to log feedback' }, { status: 500 });
  }
}