package integrations

import (
	"net/http"

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

type Prometheus struct {
	reg              *prometheus.Registry
	rpsCounter       prometheus.Counter
	avgReqTimeHist   prometheus.Histogram
	panicsHist       prometheus.Histogram
	errors4xxCounter prometheus.Counter
	errors5xxCounter prometheus.Counter
}

func NewPrometheus() *Prometheus {
	reg := prometheus.NewRegistry()

	// Add go runtime metrics and process collectors.
	reg.MustRegister(
		collectors.NewGoCollector(),
		collectors.NewProcessCollector(collectors.ProcessCollectorOpts{}),
	)

	errors5xxCounter := prometheus.NewCounter(
		prometheus.CounterOpts{
			Name: "backend_errors_count_5xx",
			Help: "5xx errors count",
		},
	)
	errors4xxCounter := prometheus.NewCounter(
		prometheus.CounterOpts{
			Name: "backend_errors_count_4xx",
			Help: "4xx errors count",
		},
	)
	rpsCounter := prometheus.NewCounter(
		prometheus.CounterOpts{
			Name: "backend_requests_per_second",
			Help: "Requests per second metric",
		},
	)
	avgReqTimeHist := prometheus.NewHistogram(
		prometheus.HistogramOpts{
			Name: "backend_requests_average_time",
			Help: "Average time of requests",
		},
	)
	panicsHist := prometheus.NewHistogram(
		prometheus.HistogramOpts{
			Name: "backend_panics",
			Help: "Panics histogram metric",
		},
	)
	reg.MustRegister(rpsCounter, avgReqTimeHist, panicsHist, errors4xxCounter, errors5xxCounter)

	return &Prometheus{
		panicsHist:       panicsHist,
		avgReqTimeHist:   avgReqTimeHist,
		rpsCounter:       rpsCounter,
		errors4xxCounter: errors4xxCounter,
		errors5xxCounter: errors5xxCounter,
		reg:              reg,
	}
}

func (p *Prometheus) GetRequestHandler() http.Handler {
	return promhttp.HandlerFor(p.reg, promhttp.HandlerOpts{Registry: p.reg})
}

func (p *Prometheus) RequestInc() {
	p.rpsCounter.Inc()
}

func (p *Prometheus) RequestDec() {
	// p.rpsGauge.Dec()
}

func (p *Prometheus) AddRequestTime(reqTime float64) {
	p.avgReqTimeHist.Observe(reqTime)
}

func (p *Prometheus) AddPanic() {
	p.panicsHist.Observe(1)
}

func (p *Prometheus) Add4xxError() {
	p.errors4xxCounter.Inc()
}

func (p *Prometheus) Add5xxError() {
	p.errors5xxCounter.Inc()
}