"use strict";

const { MeterProvider } = require('@opentelemetry/metrics');
const { PrometheusExporter } = require('@opentelemetry/exporter-prometheus');

const meter = new MeterProvider().getMeter('example-monitored');

meter.addExporter(
  new PrometheusExporter(
    {
      startServer: true
    },
    () => {
      console.log("prometheus scrape endpoint: http://localhost:9464/metrics");
    }
  )
);

const requestCount = meter.createCounter("requests", {
  monotonic: true,
  labelKeys: ["route"],
  description: "Count all incoming requests"
});

const boundInstruments = new Map();

module.exports.countAllRequests = () => {
  return (req, res, next) => {
    if (!boundInstruments.has(req.path)) {
      const labelSet = meter.labels({ route: req.path });
      const boundCounter = requestCount.bind(labelSet);
      boundInstruments.set(req.path, boundCounter);
    }

    boundInstruments.get(req.path).add(1);
    next();
  };
};