/*
Copyright 2023 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 monitor

import (
	"time"

	autoscalingv2 "k8s.io/api/autoscaling/v2"
)

// ActionLabel represents an action taken by HPA controller.
type ActionLabel string

// ErrorLabel represents an error type.
type ErrorLabel string

const (
	// ActionLabelScaleUp represents a scale up action.
	ActionLabelScaleUp ActionLabel = "scale_up"
	// ActionLabelScaleDown represents a scale down action.
	ActionLabelScaleDown ActionLabel = "scale_down"
	// ActionLabelNone represents no action.
	ActionLabelNone ActionLabel = "none"

	// ErrorLabelSpec represents an error due to an invalid spec of HPA object.
	ErrorLabelSpec ErrorLabel = "spec"
	// ErrorLabelInternal represents an error from an internal computation or communication with other component.
	ErrorLabelInternal ErrorLabel = "internal"
	// ErrorLabelNone represents no error.
	ErrorLabelNone ErrorLabel = "none"
)

// Monitor records some metrics so that people can monitor HPA controller.
type Monitor interface {
	ObserveReconciliationResult(action ActionLabel, err ErrorLabel, duration time.Duration)
	ObserveMetricComputationResult(action ActionLabel, err ErrorLabel, duration time.Duration, metricType autoscalingv2.MetricSourceType)
}

type monitor struct{}

// New creates a new Monitor.
func New() Monitor {
	return &monitor{}
}

// ObserveReconciliationResult observes some metrics from a reconciliation result.
func (r *monitor) ObserveReconciliationResult(action ActionLabel, err ErrorLabel, duration time.Duration) {
	reconciliationsTotal.WithLabelValues(string(action), string(err)).Inc()
	reconciliationsDuration.WithLabelValues(string(action), string(err)).Observe(duration.Seconds())
}

// ObserveMetricComputationResult observes some metrics from a metric computation result.
func (r *monitor) ObserveMetricComputationResult(action ActionLabel, err ErrorLabel, duration time.Duration, metricType autoscalingv2.MetricSourceType) {
	metricComputationTotal.WithLabelValues(string(action), string(err), string(metricType)).Inc()
	metricComputationDuration.WithLabelValues(string(action), string(err), string(metricType)).Observe(duration.Seconds())
}
