import { LangfuseSpanProcessor } from '@langfuse/otel';
import { NodeTracerProvider } from '@opentelemetry/sdk-trace-node';

export function register() {
  // Skip telemetry if Langfuse env vars are not configured
  if (!process.env.LANGFUSE_PUBLIC_KEY || !process.env.LANGFUSE_SECRET_KEY) {
    console.warn('[Langfuse] Environment variables not configured - telemetry disabled');
    return;
  }

  const langfuseSpanProcessor = new LangfuseSpanProcessor({
    publicKey: process.env.LANGFUSE_PUBLIC_KEY,
    secretKey: process.env.LANGFUSE_SECRET_KEY,
    baseUrl: process.env.LANGFUSE_BASEURL,
    // Filter out Next.js HTTP request spans so AI SDK spans become root traces
    shouldExportSpan: ({ otelSpan }) => {
      const spanName = otelSpan.name;
      // Skip Next.js HTTP infrastructure spans
      if (spanName.startsWith('POST /') ||
          spanName.startsWith('GET /') ||
          spanName.includes('BaseServer') ||
          spanName.includes('handleRequest')) {
        return false;
      }
      return true;
    },
  });

  const tracerProvider = new NodeTracerProvider({
    spanProcessors: [langfuseSpanProcessor],
  });

  // Register globally so AI SDK's telemetry also uses this processor
  tracerProvider.register();
}