backstack: added saving of backstack to workspace

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

@@ -0,0 +1,9 @@
+package workspaces
+
+import "github.com/lmika/audax/internal/dynamo-browse/models/serialisable"
+
+type ResultSetSnapshotStore interface {
+	Save(rs *serialisable.ResultSetSnapshot) error
+	SetAsHead(resultSetId int64) error
+	Head() (*serialisable.ResultSetSnapshot, error)
+}

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

@@ -0,0 +1,43 @@
+package workspaces
+
+import (
+	"github.com/lmika/audax/internal/dynamo-browse/models"
+	"github.com/lmika/audax/internal/dynamo-browse/models/serialisable"
+	"github.com/pkg/errors"
+	"time"
+)
+
+type Service struct {
+	store ResultSetSnapshotStore
+}
+
+func NewService(store ResultSetSnapshotStore) *Service {
+	return &Service{
+		store: store,
+	}
+}
+
+func (s *Service) PushSnapshot(rs *models.ResultSet) error {
+	newSnapshot := &serialisable.ResultSetSnapshot{
+		Time:      time.Now(),
+		TableInfo: rs.TableInfo,
+	}
+	if q := rs.Query; q != nil {
+		newSnapshot.Query.Expression = q.String()
+	}
+
+	if head, err := s.store.Head(); head != nil {
+		newSnapshot.BackLink = head.ID
+	} else if err != nil {
+		return errors.Wrap(err, "cannot get head result set")
+	}
+
+	if err := s.store.Save(newSnapshot); err != nil {
+		return errors.Wrap(err, "cannot save snapshot")
+	}
+	if err := s.store.SetAsHead(newSnapshot.ID); err != nil {
+		return errors.Wrap(err, "cannot set new snapshot as head")
+	}
+
+	return nil
+}