Issue 24: Added read-only mode (#27)

- Added settings to workspace, and added the read-only mode
- Added the `-ro` field which will launch Dynamo-Browse in read-only mode
- Added the `set ro` to enable read-only mode, and `set rw` to enable read-write mode

internal/dynamo-browse/services/tables/iface.go

@@ -17,3 +17,7 @@ type TableProvider interface {
 	PutItem(ctx context.Context, name string, item models.Item) error
 	PutItems(ctx context.Context, name string, items []models.Item) error
 }
+
+type ROProvider interface {
+	IsReadOnly() (bool, error)
+}

internal/dynamo-browse/services/tables/service.go

@@ -12,12 +12,14 @@ import (
 )
 
 type Service struct {
-	provider TableProvider
+	provider   TableProvider
+	roProvider ROProvider
 }
 
-func NewService(provider TableProvider) *Service {
+func NewService(provider TableProvider, roProvider ROProvider) *Service {
 	return &Service{
-		provider: provider,
+		provider:   provider,
+		roProvider: roProvider,
 	}
 }
 
@@ -75,10 +77,18 @@ func (s *Service) doScan(ctx context.Context, tableInfo *models.TableInfo, expr
 }
 
 func (s *Service) Put(ctx context.Context, tableInfo *models.TableInfo, item models.Item) error {
+	if err := s.assertReadWrite(); err != nil {
+		return err
+	}
+
 	return s.provider.PutItem(ctx, tableInfo.Name, item)
 }
 
 func (s *Service) PutItemAt(ctx context.Context, resultSet *models.ResultSet, index int) error {
+	if err := s.assertReadWrite(); err != nil {
+		return err
+	}
+
 	item := resultSet.Items()[index]
 	if err := s.provider.PutItem(ctx, resultSet.TableInfo.Name, item); err != nil {
 		return err
@@ -90,6 +100,10 @@ func (s *Service) PutItemAt(ctx context.Context, resultSet *models.ResultSet, in
 }
 
 func (s *Service) PutSelectedItems(ctx context.Context, resultSet *models.ResultSet, markedItems []models.ItemIndex) error {
+	if err := s.assertReadWrite(); err != nil {
+		return err
+	}
+
 	if len(markedItems) == 0 {
 		return nil
 	}
@@ -108,6 +122,10 @@ func (s *Service) PutSelectedItems(ctx context.Context, resultSet *models.Result
 }
 
 func (s *Service) Delete(ctx context.Context, tableInfo *models.TableInfo, items []models.Item) error {
+	if err := s.assertReadWrite(); err != nil {
+		return err
+	}
+
 	for _, item := range items {
 		if err := s.provider.DeleteItem(ctx, tableInfo.Name, item.KeyValue(tableInfo)); err != nil {
 			return errors.Wrapf(err, "cannot delete item")
@@ -120,6 +138,16 @@ func (s *Service) ScanOrQuery(ctx context.Context, tableInfo *models.TableInfo,
 	return s.doScan(ctx, tableInfo, expr)
 }
 
+func (s *Service) assertReadWrite() error {
+	b, err := s.roProvider.IsReadOnly()
+	if err != nil {
+		return err
+	} else if b {
+		return models.ErrReadOnly
+	}
+	return nil
+}
+
 // TODO: move into a new service
 func (s *Service) Filter(resultSet *models.ResultSet, filter string) *models.ResultSet {
 	for i, item := range resultSet.Items() {

internal/dynamo-browse/services/tables/service_test.go

@@ -19,7 +19,7 @@ func TestService_Describe(t *testing.T) {
 	t.Run("return details of the table", func(t *testing.T) {
 		ctx := context.Background()
 
-		service := tables.NewService(provider)
+		service := tables.NewService(provider, mockedReadOnlyProvider{readOnly: false})
 		ti, err := service.Describe(ctx, tableName)
 		assert.NoError(t, err)
 
@@ -40,7 +40,7 @@ func TestService_Scan(t *testing.T) {
 	t.Run("return all columns and fields in sorted order", func(t *testing.T) {
 		ctx := context.Background()
 
-		service := tables.NewService(provider)
+		service := tables.NewService(provider, mockedReadOnlyProvider{readOnly: false})
 		ti, err := service.Describe(ctx, tableName)
 		assert.NoError(t, err)
 
@@ -77,3 +77,11 @@ var testData = []testdynamo.TestData{
 		},
 	},
 }
+
+type mockedReadOnlyProvider struct {
+	readOnly bool
+}
+
+func (m mockedReadOnlyProvider) IsReadOnly() (bool, error) {
+	return m.readOnly, nil
+}