package metrics

import (
	"net/http"

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

// Metrics holds all Prometheus collectors for the honeypot.
type Metrics struct {
	registry *prometheus.Registry

	SSHConnectionsTotal  *prometheus.CounterVec
	SSHConnectionsActive prometheus.Gauge
	AuthAttemptsTotal    *prometheus.CounterVec
	SessionsTotal        *prometheus.CounterVec
	SessionsActive       prometheus.Gauge
	SessionDuration      prometheus.Histogram
	BuildInfo            *prometheus.GaugeVec
}

// New creates a new Metrics instance with all collectors registered.
func New(version string) *Metrics {
	reg := prometheus.NewRegistry()

	m := &Metrics{
		registry: reg,
		SSHConnectionsTotal: prometheus.NewCounterVec(prometheus.CounterOpts{
			Name: "oubliette_ssh_connections_total",
			Help: "Total SSH connections received.",
		}, []string{"outcome"}),
		SSHConnectionsActive: prometheus.NewGauge(prometheus.GaugeOpts{
			Name: "oubliette_ssh_connections_active",
			Help: "Current active SSH connections.",
		}),
		AuthAttemptsTotal: prometheus.NewCounterVec(prometheus.CounterOpts{
			Name: "oubliette_auth_attempts_total",
			Help: "Total authentication attempts.",
		}, []string{"result", "reason"}),
		SessionsTotal: prometheus.NewCounterVec(prometheus.CounterOpts{
			Name: "oubliette_sessions_total",
			Help: "Total sessions created.",
		}, []string{"shell"}),
		SessionsActive: prometheus.NewGauge(prometheus.GaugeOpts{
			Name: "oubliette_sessions_active",
			Help: "Current active sessions.",
		}),
		SessionDuration: prometheus.NewHistogram(prometheus.HistogramOpts{
			Name:    "oubliette_session_duration_seconds",
			Help:    "Session duration in seconds.",
			Buckets: []float64{1, 5, 10, 30, 60, 120, 300, 600, 1800, 3600},
		}),
		BuildInfo: prometheus.NewGaugeVec(prometheus.GaugeOpts{
			Name: "oubliette_build_info",
			Help: "Build information. Always 1.",
		}, []string{"version"}),
	}

	reg.MustRegister(
		collectors.NewGoCollector(),
		collectors.NewProcessCollector(collectors.ProcessCollectorOpts{}),
		m.SSHConnectionsTotal,
		m.SSHConnectionsActive,
		m.AuthAttemptsTotal,
		m.SessionsTotal,
		m.SessionsActive,
		m.SessionDuration,
		m.BuildInfo,
	)

	m.BuildInfo.WithLabelValues(version).Set(1)

	// Initialize label combinations so they appear in Gather/output.
	for _, outcome := range []string{"accepted", "rejected_handshake", "rejected_max_connections"} {
		m.SSHConnectionsTotal.WithLabelValues(outcome)
	}
	for _, reason := range []string{"static_credential", "remembered_credential", "threshold_reached", "rejected"} {
		m.AuthAttemptsTotal.WithLabelValues("accepted", reason)
		m.AuthAttemptsTotal.WithLabelValues("rejected", reason)
	}
	for _, shell := range []string{"bash", "fridge", "banking", "adventure"} {
		m.SessionsTotal.WithLabelValues(shell)
	}

	return m
}

// Handler returns an http.Handler that serves Prometheus metrics.
func (m *Metrics) Handler() http.Handler {
	return promhttp.HandlerFor(m.registry, promhttp.HandlerOpts{})
}