/*
Copyright 2018 The Kubernetes Authors.

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/

package prometheus

import (
	"github.com/prometheus/client_golang/prometheus"
	"k8s.io/client-go/tools/leaderelection"
)

// Package prometheus sets the workqueue DefaultMetricsFactory to produce
// prometheus metrics. To use this package, you just have to import it.

func init() {
	leaderelection.SetProvider(prometheusMetricsProvider{})
}

type prometheusMetricsProvider struct{}

func (prometheusMetricsProvider) NewLeaderMetric() leaderelection.SwitchMetric {
	leaderGauge := prometheus.NewGaugeVec(
		prometheus.GaugeOpts{
			Name: "leader_election_master_status",
			Help: "Gauge of if the reporting system is master of the relevant lease, 0 indicates backup, 1 indicates master. 'name' is the string used to identify the lease. Please make sure to group by name.",
		},
		[]string{"name"},
	)
	prometheus.Register(leaderGauge)
	return &switchAdapter{gauge: leaderGauge}
}

type switchAdapter struct {
	gauge *prometheus.GaugeVec
}

func (s *switchAdapter) On(name string) {
	s.gauge.WithLabelValues(name).Set(1.0)
}

func (s *switchAdapter) Off(name string) {
	s.gauge.WithLabelValues(name).Set(0.0)
}
