1 files changed, 138 insertions, 0 deletions
diff --git a/libpod/image/tree.go b/libpod/image/tree.go
new file mode 100644
index 000000000..c7c69462f
--- /dev/null
+++ b/libpod/image/tree.go
@@ -0,0 +1,138 @@
+package image
+
+import (
+	"context"
+	"fmt"
+	"strings"
+
+	"github.com/docker/go-units"
+	"github.com/pkg/errors"
+)
+
+const (
+	middleItem   = "├── "
+	continueItem = "│   "
+	lastItem     = "└── "
+)
+
+type tree struct {
+	img       *Image
+	imageInfo *InfoImage
+	layerInfo map[string]*LayerInfo
+	sb        *strings.Builder
+}
+
+// GenerateTree creates an image tree string representation for displaying it
+// to the user.
+func (i *Image) GenerateTree(whatRequires bool) (string, error) {
+	// Fetch map of image-layers, which is used for printing output.
+	layerInfo, err := GetLayersMapWithImageInfo(i.imageruntime)
+	if err != nil {
+		return "", errors.Wrapf(err, "error while retrieving layers of image %q", i.InputName)
+	}
+
+	// Create an imageInfo and fill the image and layer info
+	imageInfo := &InfoImage{
+		ID:   i.ID(),
+		Tags: i.Names(),
+	}
+
+	if err := BuildImageHierarchyMap(imageInfo, layerInfo, i.TopLayer()); err != nil {
+		return "", err
+	}
+	sb := &strings.Builder{}
+	tree := &tree{i, imageInfo, layerInfo, sb}
+	if err := tree.print(whatRequires); err != nil {
+		return "", err
+	}
+	return tree.string(), nil
+}
+
+func (t *tree) string() string {
+	return t.sb.String()
+}
+
+func (t *tree) print(whatRequires bool) error {
+	size, err := t.img.Size(context.Background())
+	if err != nil {
+		return err
+	}
+
+	fmt.Fprintf(t.sb, "Image ID: %s\n", t.imageInfo.ID[:12])
+	fmt.Fprintf(t.sb, "Tags:     %s\n", t.imageInfo.Tags)
+	fmt.Fprintf(t.sb, "Size:     %v\n", units.HumanSizeWithPrecision(float64(*size), 4))
+	if t.img.TopLayer() != "" {
+		fmt.Fprintf(t.sb, "Image Layers\n")
+	} else {
+		fmt.Fprintf(t.sb, "No Image Layers\n")
+	}
+
+	if !whatRequires {
+		// fill imageInfo with layers associated with image.
+		// the layers will be filled such that
+		// (Start)RootLayer->...intermediate Parent Layer(s)-> TopLayer(End)
+		// Build output from imageInfo into buffer
+		t.printImageHierarchy(t.imageInfo)
+	} else {
+		// fill imageInfo with layers associated with image.
+		// the layers will be filled such that
+		// (Start)TopLayer->...intermediate Child Layer(s)-> Child TopLayer(End)
+		//     (Forks)... intermediate Child Layer(s) -> Child Top Layer(End)
+		return t.printImageChildren(t.layerInfo, t.img.TopLayer(), "", true)
+	}
+	return nil
+}
+
+// Stores all children layers which are created using given Image.
+// Layers are stored as follows
+// (Start)TopLayer->...intermediate Child Layer(s)-> Child TopLayer(End)
+//             (Forks)... intermediate Child Layer(s) -> Child Top Layer(End)
+func (t *tree) printImageChildren(layerMap map[string]*LayerInfo, layerID string, prefix string, last bool) error {
+	if layerID == "" {
+		return nil
+	}
+	ll, ok := layerMap[layerID]
+	if !ok {
+		return fmt.Errorf("lookup error: layerid  %s, not found", layerID)
+	}
+	fmt.Fprint(t.sb, prefix)
+
+	//initialize intend with middleItem to reduce middleItem checks.
+	intend := middleItem
+	if !last {
+		// add continueItem i.e. '|' for next iteration prefix
+		prefix += continueItem
+	} else if len(ll.ChildID) > 1 || len(ll.ChildID) == 0 {
+		// The above condition ensure, alignment happens for node, which has more then 1 children.
+		// If node is last in printing hierarchy, it should not be printed as middleItem i.e. ├──
+		intend = lastItem
+		prefix += " "
+	}
+
+	var tags string
+	if len(ll.RepoTags) > 0 {
+		tags = fmt.Sprintf(" Top Layer of: %s", ll.RepoTags)
+	}
+	fmt.Fprintf(t.sb, "%sID: %s Size: %7v%s\n", intend, ll.ID[:12], units.HumanSizeWithPrecision(float64(ll.Size), 4), tags)
+	for count, childID := range ll.ChildID {
+		if err := t.printImageChildren(layerMap, childID, prefix, count == len(ll.ChildID)-1); err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+// prints the layers info of image
+func (t *tree) printImageHierarchy(imageInfo *InfoImage) {
+	for count, l := range imageInfo.Layers {
+		var tags string
+		intend := middleItem
+		if len(l.RepoTags) > 0 {
+			tags = fmt.Sprintf(" Top Layer of: %s", l.RepoTags)
+		}
+		if count == len(imageInfo.Layers)-1 {
+			intend = lastItem
+		}
+		fmt.Fprintf(t.sb, "%s ID: %s Size: %7v%s\n", intend, l.ID[:12], units.HumanSizeWithPrecision(float64(l.Size), 4), tags)
+	}
+}