// Package beacon spawns a goroutine that posts a version
// beacon as a statsD counter increment every hour.
package beacon

import (
	"os"
	"strings"
	"time"

	"gitlab-app.eng.qops.net/golang/metrics"
)

const (
	// MetricsPrefix is the standard qmp prefix when using the version beacon.
	MetricsPrefix = "telegraf.qmp-client"
)

// Register starts a goroutine that emits a version beacon hourly detaling the given
// application name, library name, and library version using the given prefix.
func Register(appName, libName, libVersion, metricPrefix string) {
	go func() {
		// If this returns an error, then the reporter sends metrics nowhere.
		// Does not interfere with program execution.
		reporter, _ := metrics.NewReporter(metricPrefix)
		hostname := os.Getenv("HOSTNAME")
		if hostname == "" {
			hostname = "unknown"
		}
		reporter.IncCounter(strings.Join([]string{"beacon", "go", libName}, "."),
			metrics.Tag("ver", libVersion),
			metrics.Tag("app", appName),
			metrics.Tag("host", hostname),
		)
		ticker := time.NewTicker(time.Hour)
		for range ticker.C {
			reporter.IncCounter(strings.Join([]string{"beacon", "go", libName}, "."),
				metrics.Tag("ver", libVersion),
				metrics.Tag("app", appName),
				metrics.Tag("host", hostname),
			)
		}
	}()
}