package exmo

import (
	"errors"
	"fmt"
	"io"
	"io/ioutil"
	"log"
	"net"
	"net/http"
	"time"

	"github.com/prometheus/client_golang/prometheus"
)

func Metrics(addr string) error {
	http.Handle("/metrics", prometheus.Handler())
	h, p, err := net.SplitHostPort(addr)
	if err != nil {
		return err
	}
	var u string
	if h != "" {
		u = fmt.Sprintf("http://%v:%v/metrics", h, p)
	} else {
		u = fmt.Sprintf("http://localhost:%v/metrics", p)
	}
	e := make(chan error)

	go func() {
		err := http.ListenAndServe(addr, nil)
		if err != nil {
			log.Printf("%+v", err)
		}
		e <- err
	}()

	go func() {
		t := 100 * time.Millisecond
		for {
			time.Sleep(t)
			if t < time.Minute {
				t = t * 2
			}
			if t > 5*time.Second {
				e <- errors.New("timeout waiting for metrics server to start")
			}

			resp, err := http.Get(u)
			if err != nil {
				log.Printf("%+v", err)
				continue
			}
			io.Copy(ioutil.Discard, resp.Body)
			if resp.StatusCode != http.StatusOK {
				log.Printf("%+v", resp.Status)
			} else {
				e <- nil
				return
			}
		}
	}()

	return <-e
}