package observability

import (
	"net/http"

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

// HTTPMetrics contains metric collectors used by HTTP middleware.
type HTTPMetrics struct {
	RequestsTotal   *prometheus.CounterVec
	RequestDuration *prometheus.HistogramVec
	InFlight        prometheus.Gauge
}

func NewRegistry() *prometheus.Registry {
	registry := prometheus.NewRegistry()
	registry.MustRegister(
		collectors.NewGoCollector(),
		collectors.NewProcessCollector(collectors.ProcessCollectorOpts{}),
	)
	return registry
}

func NewHTTPMetrics(registerer prometheus.Registerer) *HTTPMetrics {
	factory := promauto.With(registerer)

	return &HTTPMetrics{
		RequestsTotal: factory.NewCounterVec(
			prometheus.CounterOpts{
				Name: "http_requests_total",
				Help: "Total number of HTTP requests by method, route, and status.",
			},
			[]string{"method", "route", "status"},
		),
		RequestDuration: factory.NewHistogramVec(
			prometheus.HistogramOpts{
				Name:    "http_request_duration_seconds",
				Help:    "HTTP request duration by method, route, and status.",
				Buckets: prometheus.DefBuckets,
			},
			[]string{"method", "route", "status"},
		),
		InFlight: factory.NewGauge(
			prometheus.GaugeOpts{
				Name: "http_in_flight_requests",
				Help: "Current number of in-flight HTTP requests.",
			},
		),
	}
}

func NewPrometheusHandler(registry *prometheus.Registry) http.Handler {
	return promhttp.HandlerFor(registry, promhttp.HandlerOpts{})
}