package collector

import (
	"sync"

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

// Group registers multiple device collectors as one Prometheus collector.
// Collecting devices concurrently prevents one slow device from delaying all others.
type Group []prometheus.Collector

// Describe forwards descriptors from every registered device collector.
func (group Group) Describe(channel chan<- *prometheus.Desc) {
	for _, deviceCollector := range group {
		deviceCollector.Describe(channel)
	}
}

// Collect scrapes all configured devices concurrently.
func (group Group) Collect(channel chan<- prometheus.Metric) {
	var waitGroup sync.WaitGroup
	waitGroup.Add(len(group))
	for _, deviceCollector := range group {
		go func(current prometheus.Collector) {
			defer waitGroup.Done()
			current.Collect(channel)
		}(deviceCollector)
	}
	waitGroup.Wait()
}