package mongo

import (
	"context"
	"log"
	"time"

	"git.k-space.ee/k-space/logmower-shipper/pkg/globals"
	prom "github.com/prometheus/client_golang/prometheus"
	"github.com/prometheus/client_golang/prometheus/promauto"
	mongoEvent "go.mongodb.org/mongo-driver/event"
	mongoOpt "go.mongodb.org/mongo-driver/mongo/options"
)

const promSubsystem = "database"

var (
	promDbHeartbeat = promauto.NewHistogramVec(prom.HistogramOpts{
		Namespace: globals.PrometheusPrefix, Subsystem: promSubsystem,
		Name:    "heartbeat_time",
		Help:    "Time in seconds for succeeded heartbeat, or 0 on failure",
		Buckets: []float64{0.1, 0.2, 0.5, 1, 5, 10, 50},
	}, []string{"connection_id"})

	promDbCmd = promauto.NewHistogramVec(prom.HistogramOpts{
		Namespace: globals.PrometheusPrefix, Subsystem: promSubsystem,
		Name:    "operation_latency", // "command_time",
		Help:    "Time in seconds of commands",
		Buckets: []float64{0.1, 0.2, 0.5, 1, 5, 10, 50},
	}, []string{"connection_id", "command_name"})

	promDbCmdErr = promauto.NewCounterVec(prom.CounterOpts{
		Namespace: globals.PrometheusPrefix, Subsystem: promSubsystem,
		Name: "errors",
		Help: "Failed commands (also reflected elsewhere)",
	}, []string{"connection_id", "command_name"})
)

func monitoredClientOptions() *mongoOpt.ClientOptions {
	return mongoOpt.Client().
		SetServerMonitor(&mongoEvent.ServerMonitor{
			ServerHeartbeatSucceeded: func(ev *mongoEvent.ServerHeartbeatSucceededEvent) {
				promDbHeartbeat.WithLabelValues(ev.ConnectionID).Observe(time.Duration(ev.DurationNanos).Seconds())
			},
			ServerHeartbeatFailed: func(ev *mongoEvent.ServerHeartbeatFailedEvent) {
				promDbHeartbeat.WithLabelValues(ev.ConnectionID).Observe(0)
				log.Printf("database heartbeat failed on connection %q: %e", ev.ConnectionID, ev.Failure)
			},
		}).
		SetMonitor(&mongoEvent.CommandMonitor{
			Succeeded: func(_ context.Context, ev *mongoEvent.CommandSucceededEvent) {
				promDbCmd.WithLabelValues(ev.ConnectionID, ev.CommandName).Observe(time.Duration(ev.DurationNanos).Seconds())
			},
			Failed: func(_ context.Context, ev *mongoEvent.CommandFailedEvent) {
				promDbCmd.WithLabelValues(ev.ConnectionID, ev.CommandName).Observe(time.Duration(ev.DurationNanos).Seconds())

				promDbCmdErr.WithLabelValues(ev.ConnectionID, ev.CommandName).Add(1)
			},
		})
}