feat: start working on a state-machine for pulls

Author: silenium-dev

pkg/client/pull/state/state.go

@@ -0,0 +1,52 @@
+package state
+
+import (
+	"github.com/distribution/reference"
+	"github.com/opencontainers/go-digest"
+)
+
+type Pull interface {
+	Ref() reference.Named
+	Digest() *digest.Digest // can be nil when the pull is not yet complete
+	Layers() []Layer
+	Layer(id string) Layer
+}
+
+type Layer interface {
+	Id() string
+	Status() string
+}
+
+type pullBase struct {
+	ref    reference.Named
+	layers []Layer
+}
+
+func (p *pullBase) Ref() reference.Named {
+	return p.ref
+}
+
+func (p *pullBase) Digest() *digest.Digest {
+	return nil
+}
+
+func (p *pullBase) Layers() []Layer {
+	return p.layers
+}
+
+func (p *pullBase) Layer(id string) Layer {
+	for _, l := range p.layers {
+		if l.Id() == id {
+			return l
+		}
+	}
+	return nil
+}
+
+type layerBase struct {
+	id string
+}
+
+func (l *layerBase) Id() string {
+	return l.id
+}