package main

import (
	"context"
	"log/slog"
	"net/http"
	"os"
	"time"

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

var (
	times = promauto.NewHistogramVec(prometheus.HistogramOpts{
		Name:    "app_times_seconds",
		Buckets: []float64{0.01, 0.013, 0.015, 0.02, 0.03, 0.04, 0.05, 0.06, 1, 2, 3, 4, 5, 6, 7},
	}, []string{"status"})
	timesSummary = promauto.NewSummaryVec(prometheus.SummaryOpts{
		Name:       "app_times_summary_seconds",
		Objectives: map[float64]float64{0.5: 0.05, 0.9: 0.01, 0.99: 0.001},
	}, []string{"status"})
	timesNative = promauto.NewHistogramVec(prometheus.HistogramOpts{
		Name:                        "app_times_native_seconds",
		NativeHistogramBucketFactor: 1.1,
	}, []string{"status"})
)

func main() {
	slog.Info("application started")
	if err := start(context.Background()); err != nil {
		slog.Error("unable to start application", "error", err)
		os.Exit(1)
	}

	slog.Info("application stopped")
}

func start(_ context.Context) error {
	port := os.Getenv("APP_PORT")
	go func() {
		var max time.Duration
		for {
			t := time.Now()
			time.Sleep(10 * time.Millisecond)
			duration := time.Since(t)
			times.WithLabelValues("10ms").Observe(duration.Seconds())
			timesNative.WithLabelValues("10ms").Observe(duration.Seconds())
			timesSummary.WithLabelValues("10ms").Observe(duration.Seconds())
			if duration > max {
				max = duration
			}
			slog.Info("duration", "duration", duration, "max", max)
		}
	}()
	go func() {
		var max time.Duration
		for {
			t := time.Now()
			time.Sleep(100 * time.Millisecond)
			duration := time.Since(t)
			times.WithLabelValues("100ms").Observe(duration.Seconds())
			timesNative.WithLabelValues("100ms").Observe(duration.Seconds())
			timesSummary.WithLabelValues("100ms").Observe(duration.Seconds())
			if duration > max {
				max = duration
			}
			// slog.Info("duration", "duration", duration, "max", max)
		}
	}()

	http.Handle("/metrics", promhttp.Handler())
	return http.ListenAndServe(":"+port, nil)
}