//go:build linux

package service

import (
	"context"
	"os"
	"strconv"
	"time"

	"github.com/coreos/go-systemd/v22/daemon"
)

// NotifyReady tells systemd the service is up (Type=notify). It is a no-op
// when NOTIFY_SOCKET is unset, e.g. in a container or interactive shell.
func NotifyReady() {
	daemon.SdNotify(false, daemon.SdNotifyReady)
}

// NotifyStopping tells systemd the service is shutting down.
func NotifyStopping() {
	daemon.SdNotify(false, daemon.SdNotifyStopping)
}

// StartWatchdog pings the systemd watchdog every half of WATCHDOG_USEC
// until ctx is cancelled. It is a no-op unless systemd started the process
// with a watchdog configured (WatchdogSec= in the unit).
func StartWatchdog(ctx context.Context) {
	usec, err := strconv.Atoi(os.Getenv("WATCHDOG_USEC"))
	if err != nil || usec <= 0 {
		return
	}
	interval := time.Duration(usec) * time.Microsecond / 2
	go func() {
		ticker := time.NewTicker(interval)
		defer ticker.Stop()
		for {
			select {
			case <-ctx.Done():
				return
			case <-ticker.C:
				daemon.SdNotify(false, daemon.SdNotifyWatchdog)
			}
		}
	}()
}