util: add progress handling primitive

Signed-off-by: Tonis Tiigi <tonistiigi@gmail.com>

util/progress/progress.go

@@ -0,0 +1,62 @@
+package progress
+
+import (
+	"context"
+	"time"
+
+	"github.com/pkg/errors"
+)
+
+func FromContext(ctx context.Context, name string) (*ProgressWriter, bool, context.Context) {
+	return nil, false, ctx
+}
+
+func NewContext(ctx context.Context) (*ProgressReader, context.Context) {
+	return nil, ctx
+}
+
+type ProgressWriter interface {
+	Write(Progress) error
+	Done() error
+}
+
+type ProgressReader interface {
+	Read(context.Context) (*Progress, error)
+}
+
+type Progress struct {
+	ID string
+
+	// Progress contains a Message or...
+	Message string
+
+	// ...progress of an action
+	Action    string
+	Current   int64
+	Total     int64
+	Timestamp time.Time
+	Done      bool
+}
+
+type progressReader struct{}
+
+func (pr *progressReader) Read(ctx context.Context) (*Progress, error) {
+	return nil, errors.Errorf("Read not implemented")
+}
+
+type progressWriter struct{}
+
+func (pw *progressWriter) Write(p Progress) error {
+	return errors.Errorf("Write not implemented")
+}
+
+func (pw *progressWriter) Done() error {
+	return errors.Errorf("Done not implemented")
+}
+
+// type ProgressRecord struct {
+// 	UUID   string
+// 	Parent string
+// 	Done   bool
+// 	*Progress
+// }