Simplified loop mechanism for openvpn and dns

- Refers to #91
- http control server starts without waiting for unbound and/or openvpn
- Trying to get rid of waiter and use channels directly
- Simpler main.go
- More robust logic overall

internal/openvpn/loop.go

@@ -0,0 +1,76 @@
+package openvpn
+
+import (
+	"context"
+	"fmt"
+	"time"
+
+	"github.com/qdm12/golibs/command"
+	"github.com/qdm12/golibs/logging"
+	"github.com/qdm12/private-internet-access-docker/internal/constants"
+	"github.com/qdm12/private-internet-access-docker/internal/settings"
+)
+
+type Looper interface {
+	Run(ctx context.Context, restart <-chan struct{}, done chan<- struct{})
+}
+
+type looper struct {
+	conf         Configurator
+	settings     settings.OpenVPN
+	logger       logging.Logger
+	streamMerger command.StreamMerger
+	fatalOnError func(err error)
+}
+
+func NewLooper(conf Configurator, settings settings.OpenVPN, logger logging.Logger,
+	streamMerger command.StreamMerger, fatalOnError func(err error)) Looper {
+	return &looper{
+		conf:         conf,
+		settings:     settings,
+		logger:       logger.WithPrefix("openvpn: "),
+		streamMerger: streamMerger,
+		fatalOnError: fatalOnError,
+	}
+}
+
+func (l *looper) Run(ctx context.Context, restart <-chan struct{}, done chan<- struct{}) {
+	select {
+	case <-restart:
+	case <-ctx.Done():
+		close(done)
+		return
+	}
+	for {
+		openvpnCtx, openvpnCancel := context.WithCancel(ctx)
+		stream, waitFn, err := l.conf.Start(openvpnCtx)
+		l.fatalOnError(err)
+		go l.streamMerger.Merge(openvpnCtx, stream,
+			command.MergeName("openvpn"), command.MergeColor(constants.ColorOpenvpn()))
+		waitError := make(chan error)
+		go func() {
+			err := waitFn() // blocking
+			if openvpnCtx.Err() != context.Canceled {
+				waitError <- fmt.Errorf("openvpn: %w", err)
+			}
+		}()
+		select {
+		case <-ctx.Done():
+			l.logger.Warn("context canceled: exiting loop")
+			openvpnCancel()
+			close(waitError)
+			close(done)
+			return
+		case <-restart: // triggered restart
+			l.logger.Info("restarting")
+			openvpnCancel()
+			close(waitError)
+		case err := <-waitError: // unexpected error
+			l.logger.Warn(err)
+			l.logger.Info("restarting")
+			openvpnCancel()
+			close(waitError)
+			time.Sleep(time.Second)
+		}
+	}
+}