import { FastifyInstance, FastifyRequest, FastifyReply } from 'fastify';
import { emitLatency, emitRequestCount, emitError } from '@shieldai/monitoring';

const SERVICE_NAME = process.env.DD_SERVICE || 'shieldai-api';

export async function monitoringMiddleware(fastify: FastifyInstance) {
  fastify.addHook('onResponse', async (request: FastifyRequest, reply: FastifyReply) => {
    const statusCode = reply.statusCode;
    const responseTime = reply.elapsedTime;
    const method = request.method;
    const url = request.url;

    // Emit request count
    await emitRequestCount(SERVICE_NAME, statusCode);

    // Emit latency metrics
    await emitLatency(SERVICE_NAME, responseTime, 'p50');
    await emitLatency(SERVICE_NAME, responseTime, 'p95');
    await emitLatency(SERVICE_NAME, responseTime, 'p99');

    // Emit error metric for 5xx
    if (statusCode >= 500) {
      await emitError(SERVICE_NAME, 'server_error');
      fastify.log.warn({
        event: 'high_latency_or_error',
        method,
        url,
        statusCode,
        responseTime,
        service: SERVICE_NAME,
      });
    }

    // Log high latency requests (>2s)
    if (responseTime > 2000) {
      fastify.log.warn({
        event: 'high_latency',
        method,
        url,
        statusCode,
        responseTime,
        service: SERVICE_NAME,
      });
    }
  });
}