// Package metrics exposes Prometheus counters/gauges/histograms for HTTP,
// TCP/UDP, backend, and TLS activity.
package metrics

import (
	"net/http"

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

var (
	HTTPRequestsTotal = promauto.NewCounterVec(prometheus.CounterOpts{
		Name: "vibeproxy_http_requests_total",
		Help: "Total HTTP requests handled by the proxy.",
	}, []string{"proxy_host", "method", "status"})

	HTTPRequestDuration = promauto.NewHistogramVec(prometheus.HistogramOpts{
		Name:    "vibeproxy_http_request_duration_seconds",
		Help:    "HTTP request latency observed by the proxy, end to end.",
		Buckets: prometheus.DefBuckets,
	}, []string{"proxy_host"})

	BackendRequestDuration = promauto.NewHistogramVec(prometheus.HistogramOpts{
		Name:    "vibeproxy_backend_request_duration_seconds",
		Help:    "Backend response latency as observed by the proxy.",
		Buckets: prometheus.DefBuckets,
	}, []string{"proxy_host", "backend"})

	BytesTransferred = promauto.NewCounterVec(prometheus.CounterOpts{
		Name: "vibeproxy_bytes_transferred_total",
		Help: "Bytes transferred through the proxy.",
	}, []string{"direction", "protocol"}) // direction=in|out, protocol=http|tcp|udp

	ActiveConnections = promauto.NewGaugeVec(prometheus.GaugeOpts{
		Name: "vibeproxy_active_connections",
		Help: "Currently active connections.",
	}, []string{"protocol"}) // http|tcp|udp

	BackendHealth = promauto.NewGaugeVec(prometheus.GaugeOpts{
		Name: "vibeproxy_backend_healthy",
		Help: "1 if the backend is currently considered healthy, else 0.",
	}, []string{"proxy_host", "backend"})

	TCPConnectionsTotal = promauto.NewCounterVec(prometheus.CounterOpts{
		Name: "vibeproxy_tcp_connections_total",
		Help: "Total TCP stream connections accepted.",
	}, []string{"stream"})

	UDPPacketsTotal = promauto.NewCounterVec(prometheus.CounterOpts{
		Name: "vibeproxy_udp_packets_total",
		Help: "Total UDP packets proxied.",
	}, []string{"stream", "direction"})

	TLSHandshakesTotal = promauto.NewCounterVec(prometheus.CounterOpts{
		Name: "vibeproxy_tls_handshakes_total",
		Help: "Total TLS handshakes, by result.",
	}, []string{"result"}) // ok|error

	CertificateExpirySeconds = promauto.NewGaugeVec(prometheus.GaugeOpts{
		Name: "vibeproxy_certificate_expiry_seconds",
		Help: "Seconds until certificate expiry (negative if already expired).",
	}, []string{"name"})
)

func Handler() http.Handler {
	return promhttp.Handler()
}