Maint: port forwarding refactoring (#543)

- portforward package
- portforward run loop
- Less functional arguments and cycles

internal/portforward/state/settings.go

@@ -0,0 +1,55 @@
+package state
+
+import (
+	"context"
+	"os"
+	"reflect"
+
+	"github.com/qdm12/gluetun/internal/configuration"
+	"github.com/qdm12/gluetun/internal/constants"
+)
+
+type SettingsGetSetter interface {
+	GetSettings() (settings configuration.PortForwarding)
+	SetSettings(ctx context.Context,
+		settings configuration.PortForwarding) (outcome string)
+}
+
+func (s *State) GetSettings() (settings configuration.PortForwarding) {
+	s.settingsMu.RLock()
+	defer s.settingsMu.RUnlock()
+	return s.settings
+}
+
+func (s *State) SetSettings(ctx context.Context, settings configuration.PortForwarding) (
+	outcome string) {
+	s.settingsMu.Lock()
+
+	settingsUnchanged := reflect.DeepEqual(s.settings, settings)
+	if settingsUnchanged {
+		s.settingsMu.Unlock()
+		return "settings left unchanged"
+	}
+
+	if s.settings.Filepath != settings.Filepath {
+		_ = os.Rename(s.settings.Filepath, settings.Filepath)
+	}
+
+	newEnabled := settings.Enabled
+	previousEnabled := s.settings.Enabled
+
+	s.settings = settings
+	s.settingsMu.Unlock()
+
+	switch {
+	case !newEnabled && !previousEnabled:
+	case newEnabled && previousEnabled:
+		// no need to restart for now since we os.Rename the file here.
+	case newEnabled && !previousEnabled:
+		_, _ = s.statusApplier.ApplyStatus(ctx, constants.Running)
+	case !newEnabled && previousEnabled:
+		_, _ = s.statusApplier.ApplyStatus(ctx, constants.Stopped)
+	}
+
+	return "settings updated"
+}