Maint: dns package state rework

- Interface composition with loopstate interfaces
- Use loopstate.Manager
- Create dns/state package for handling settings

internal/dns/state/settings.go

@@ -0,0 +1,51 @@
+package state
+
+import (
+	"context"
+	"reflect"
+
+	"github.com/qdm12/gluetun/internal/configuration"
+	"github.com/qdm12/gluetun/internal/constants"
+)
+
+type SettingsGetterSetter interface {
+	GetSettings() (settings configuration.DNS)
+	SetSettings(ctx context.Context,
+		settings configuration.DNS) (outcome string)
+}
+
+func (s *State) GetSettings() (settings configuration.DNS) {
+	s.settingsMu.RLock()
+	defer s.settingsMu.RUnlock()
+	return s.settings
+}
+
+func (s *State) SetSettings(ctx context.Context, settings configuration.DNS) (
+	outcome string) {
+	s.settingsMu.Lock()
+	defer s.settingsMu.Unlock()
+
+	settingsUnchanged := reflect.DeepEqual(s.settings, settings)
+	if settingsUnchanged {
+		return "settings left unchanged"
+	}
+
+	// Check for only update period change
+	tempSettings := s.settings
+	tempSettings.UpdatePeriod = settings.UpdatePeriod
+	onlyUpdatePeriodChanged := reflect.DeepEqual(tempSettings, settings)
+
+	s.settings = settings
+
+	if onlyUpdatePeriodChanged {
+		s.updateTicker <- struct{}{}
+		return "update period changed"
+	}
+
+	// Restart
+	_, _ = s.statusApplier.ApplyStatus(ctx, constants.Stopped)
+	if settings.Enabled {
+		outcome, _ = s.statusApplier.ApplyStatus(ctx, constants.Running)
+	}
+	return outcome
+}

internal/dns/state/state.go

@@ -0,0 +1,33 @@
+package state
+
+import (
+	"sync"
+
+	"github.com/qdm12/gluetun/internal/configuration"
+	"github.com/qdm12/gluetun/internal/loopstate"
+)
+
+var _ Manager = (*State)(nil)
+
+type Manager interface {
+	SettingsGetterSetter
+}
+
+func New(statusApplier loopstate.Applier,
+	settings configuration.DNS,
+	updateTicker chan<- struct{}) *State {
+	return &State{
+		statusApplier: statusApplier,
+		settings:      settings,
+		updateTicker:  updateTicker,
+	}
+}
+
+type State struct {
+	statusApplier loopstate.Applier
+
+	settings   configuration.DNS
+	settingsMu sync.RWMutex
+
+	updateTicker chan<- struct{}
+}