package metrics

import (
	"expvar"
	"strconv"
	"time"

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

var (
	Registry = prometheus.NewRegistry()

	HTTPRequestsTotal = prometheus.NewCounterVec(prometheus.CounterOpts{
		Name: "http_requests_total",
		Help: "Total number of HTTP requests by method, normalized path, and status.",
	}, []string{"method", "path", "status"})

	HTTPRequestDuration = prometheus.NewHistogramVec(prometheus.HistogramOpts{
		Name:    "http_request_duration_seconds",
		Help:    "HTTP request duration by method, normalized path, and status.",
		Buckets: []float64{0.005, 0.01, 0.025, 0.05, 0.1, 0.25, 0.5, 1, 2.5, 5, 10},
	}, []string{"method", "path", "status"})

	DBQueryDuration = prometheus.NewHistogramVec(prometheus.HistogramOpts{
		Name:    "db_query_duration_seconds",
		Help:    "Database operation duration by driver, operation, and status.",
		Buckets: []float64{0.001, 0.003, 0.005, 0.01, 0.025, 0.05, 0.1, 0.25, 0.5, 1, 2.5, 5},
	}, []string{"driver", "operation", "status"})

	WSConnectionsActive = prometheus.NewGaugeFunc(prometheus.GaugeOpts{
		Name: "ws_connections_active",
		Help: "Current active WebSocket connections.",
	}, func() float64 {
		return float64(expvarIntValue("LiveSessions"))
	})
)

func init() {
	Registry.MustRegister(WSConnectionsActive, HTTPRequestsTotal, HTTPRequestDuration, DBQueryDuration)
}

func ObserveDB(driverName, operation string, started time.Time, err error) {
	status := "ok"
	if err != nil {
		status = "error"
	}
	DBQueryDuration.WithLabelValues(driverName, operation, status).Observe(time.Since(started).Seconds())
}

func expvarIntValue(name string) int64 {
	value := expvar.Get(name)
	if value == nil {
		return 0
	}
	n, err := strconv.ParseInt(value.String(), 10, 64)
	if err != nil {
		return 0
	}
	return n
}