package main

import (
	"context"
	"log"
	"net/http"
	"os/signal"
	"syscall"
	"time"

	"github.com/VictoriaMetrics/metrics"
)

// Register various metrics.
// Metric name may contain labels in Prometheus format - see below.
var (
	// Register counter without labels.
	// requestsTotal = metrics.NewCounter("requests_total")

	requestsTotal = metrics.GetOrCreateCounter("requests_total")

	// Register summary with a single label.
	requestDuration = metrics.NewSummary(`requests_duration_seconds{path="/foobar/baz"}`)

	// Register gauge with two labels.
	// queueSize = metrics.NewGauge(`queue_size{queue="foobar",topic="baz"}`, func() float64 {
	// 	return float64(foobarQueue.Len())
	// })

	// Register histogram with a single label.
	// responseSize = metrics.NewHistogram(`response_size{path="/foo/bar"}`)
)

func main() {
	metrics.ExposeMetadata(true)

	http.HandleFunc("/", Recovery(Metrics(rootHandler)))

	// Expose the registered metrics at `/metrics` path.
	http.HandleFunc("/metrics", Recovery(metricsHandler))

	http.HandleFunc("/hello", Recovery(Metrics(helloHandler)))

	go func() {
		if err := http.ListenAndServe(":8080", nil); err != nil {
			log.Fatalln(err)
		}
	}()

	ctx, cancel := signal.NotifyContext(context.Background(), syscall.SIGINT, syscall.SIGTERM)
	defer cancel()

	<-ctx.Done()

}

func rootHandler(w http.ResponseWriter, req *http.Request) {
	w.Write([]byte("Simple GoLang metrics service"))
}

// metricsHandler ...
func metricsHandler(w http.ResponseWriter, req *http.Request) {
	metrics.WritePrometheus(w, true)
}

// helloHandler ...
func helloHandler(w http.ResponseWriter, req *http.Request) {
	w.Write([]byte("Test /hello location. hjdklfhskfhsdh"))
}

// Metrics ...
func Metrics(h http.HandlerFunc) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		requestsTotal.Inc()

		startTime := time.Now()

		h(w, r)

		requestDuration.UpdateDuration(startTime)
	}
}

// Recovery ...
func Recovery(h http.HandlerFunc) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		defer func() {
			if err := recover(); err != nil {
				log.Println(err)
			}
		}()

		h(w, r)
	}
}