package metrics

import (
	"net/http"
	"time"

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

var (
	registry = prometheus.NewRegistry()

	HourlySnapshotTotal    = prometheus.NewCounter(prometheus.CounterOpts{Name: "vctp_hourly_snapshots_total", Help: "Total number of hourly snapshot jobs completed."})
	HourlySnapshotFailures = prometheus.NewCounter(prometheus.CounterOpts{Name: "vctp_hourly_snapshots_failed_total", Help: "Hourly snapshot jobs that failed."})
	HourlySnapshotLast     = prometheus.NewGauge(prometheus.GaugeOpts{Name: "vctp_hourly_snapshot_last_unix", Help: "Unix timestamp of the last hourly snapshot start time."})
	HourlySnapshotRows     = prometheus.NewGauge(prometheus.GaugeOpts{Name: "vctp_hourly_snapshot_last_rows", Help: "Row count of the last hourly snapshot table."})

	DailyAggregationsTotal   = prometheus.NewCounter(prometheus.CounterOpts{Name: "vctp_daily_aggregations_total", Help: "Total number of daily aggregation jobs completed."})
	DailyAggregationFailures = prometheus.NewCounter(prometheus.CounterOpts{Name: "vctp_daily_aggregations_failed_total", Help: "Daily aggregation jobs that failed."})
	DailyAggregationDuration = prometheus.NewHistogram(prometheus.HistogramOpts{
		Name:    "vctp_daily_aggregation_duration_seconds",
		Help:    "Duration of daily aggregation jobs.",
		Buckets: prometheus.ExponentialBuckets(1, 2, 10),
	})

	MonthlyAggregationsTotal   = prometheus.NewCounter(prometheus.CounterOpts{Name: "vctp_monthly_aggregations_total", Help: "Total number of monthly aggregation jobs completed."})
	MonthlyAggregationFailures = prometheus.NewCounter(prometheus.CounterOpts{Name: "vctp_monthly_aggregations_failed_total", Help: "Monthly aggregation jobs that failed."})
	MonthlyAggregationDuration = prometheus.NewHistogram(prometheus.HistogramOpts{
		Name:    "vctp_monthly_aggregation_duration_seconds",
		Help:    "Duration of monthly aggregation jobs.",
		Buckets: prometheus.ExponentialBuckets(1, 2, 10),
	})

	ReportsAvailable = prometheus.NewGauge(prometheus.GaugeOpts{
		Name: "vctp_reports_available",
		Help: "Number of downloadable reports present on disk.",
	})

	VcenterConnectFailures = prometheus.NewCounterVec(prometheus.CounterOpts{
		Name: "vctp_vcenter_connect_failures_total",
		Help: "Failed connections to vCenter during snapshot runs.",
	}, []string{"vcenter"})

	VcenterSnapshotDuration = prometheus.NewHistogramVec(prometheus.HistogramOpts{
		Name:    "vctp_vcenter_snapshot_duration_seconds",
		Help:    "Duration of per-vCenter hourly snapshot jobs.",
		Buckets: prometheus.ExponentialBuckets(0.5, 2, 10),
	}, []string{"vcenter"})

	VcenterInventorySize = prometheus.NewGaugeVec(prometheus.GaugeOpts{
		Name: "vctp_vcenter_inventory_size",
		Help: "Number of VMs seen in the last successful snapshot per vCenter.",
	}, []string{"vcenter"})
)

func init() {
	registry.MustRegister(
		HourlySnapshotTotal,
		HourlySnapshotFailures,
		HourlySnapshotLast,
		HourlySnapshotRows,
		DailyAggregationsTotal,
		DailyAggregationFailures,
		DailyAggregationDuration,
		MonthlyAggregationsTotal,
		MonthlyAggregationFailures,
		MonthlyAggregationDuration,
		ReportsAvailable,
		VcenterConnectFailures,
		VcenterSnapshotDuration,
		VcenterInventorySize,
	)
}

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

// RecordVcenterSnapshot logs per-vCenter snapshot metrics.
func RecordVcenterSnapshot(vcenter string, duration time.Duration, vmCount int64, err error) {
	VcenterSnapshotDuration.WithLabelValues(vcenter).Observe(duration.Seconds())
	if err != nil {
		VcenterConnectFailures.WithLabelValues(vcenter).Inc()
		return
	}
	VcenterInventorySize.WithLabelValues(vcenter).Set(float64(vmCount))
}

// RecordHourlySnapshot logs aggregate hourly snapshot results.
func RecordHourlySnapshot(start time.Time, rows int64, err error) {
	HourlySnapshotLast.Set(float64(start.Unix()))
	HourlySnapshotRows.Set(float64(rows))
	if err != nil {
		HourlySnapshotFailures.Inc()
		return
	}
	HourlySnapshotTotal.Inc()
}

// RecordDailyAggregation logs daily aggregation metrics.
func RecordDailyAggregation(duration time.Duration, err error) {
	DailyAggregationDuration.Observe(duration.Seconds())
	if err != nil {
		DailyAggregationFailures.Inc()
		return
	}
	DailyAggregationsTotal.Inc()
}

// RecordMonthlyAggregation logs monthly aggregation metrics.
func RecordMonthlyAggregation(duration time.Duration, err error) {
	MonthlyAggregationDuration.Observe(duration.Seconds())
	if err != nil {
		MonthlyAggregationFailures.Inc()
		return
	}
	MonthlyAggregationsTotal.Inc()
}

// SetReportsAvailable updates the gauge for report files found on disk.
func SetReportsAvailable(count int) {
	ReportsAvailable.Set(float64(count))
}