/*
Copyright 2019 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 legacyregistry

import (
	"net/http"
	"time"

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

	"k8s.io/component-base/metrics"
)

var (
	defaultRegistry = metrics.NewKubeRegistry()
	// DefaultGatherer exposes the global registry gatherer
	DefaultGatherer metrics.Gatherer = defaultRegistry
	// Reset calls reset on the global registry
	Reset = defaultRegistry.Reset
	// MustRegister registers registerable metrics but uses the global registry.
	MustRegister = defaultRegistry.MustRegister
	// RawMustRegister registers prometheus collectors but uses the global registry, this
	// bypasses the metric stability framework
	//
	// Deprecated
	RawMustRegister = defaultRegistry.RawMustRegister

	// Register registers a collectable metric but uses the global registry
	Register = defaultRegistry.Register

	// Registerer exposes the global registerer
	Registerer = defaultRegistry.Registerer

	processStart time.Time
)

func init() {
	RawMustRegister(collectors.NewProcessCollector(collectors.ProcessCollectorOpts{}))
	RawMustRegister(collectors.NewGoCollector(collectors.WithGoCollectorRuntimeMetrics(collectors.MetricsAll)))
	defaultRegistry.RegisterMetaMetrics()
	processStart = time.Now()
}

// Handler returns an HTTP handler for the DefaultGatherer. It is
// already instrumented with InstrumentHandler (using "prometheus" as handler
// name).
func Handler() http.Handler {
	return promhttp.InstrumentMetricHandler(prometheus.DefaultRegisterer, promhttp.HandlerFor(defaultRegistry, promhttp.HandlerOpts{ProcessStartTime: processStart}))
}

// HandlerWithReset returns an HTTP handler for the DefaultGatherer but invokes
// registry reset if the http method is DELETE.
func HandlerWithReset() http.Handler {
	return promhttp.InstrumentMetricHandler(
		prometheus.DefaultRegisterer,
		metrics.HandlerWithReset(defaultRegistry, metrics.HandlerOpts{ProcessStartTime: processStart}))
}

// CustomRegister registers a custom collector but uses the global registry.
func CustomRegister(c metrics.StableCollector) error {
	err := defaultRegistry.CustomRegister(c)

	//TODO(RainbowMango): Maybe we can wrap this error by error wrapping.(Golang 1.13)
	_ = prometheus.Register(c)

	return err
}

// CustomMustRegister registers custom collectors but uses the global registry.
func CustomMustRegister(cs ...metrics.StableCollector) {
	defaultRegistry.CustomMustRegister(cs...)

	for _, c := range cs {
		prometheus.MustRegister(c)
	}
}
