efficiency: track which layers a file was in

dive/filetree/efficiency.go

@@ -12,6 +12,15 @@ type EfficiencyData struct {
 	Nodes             []*FileNode
 	CumulativeSize    int64
 	minDiscoveredSize int64
+	Layers            []int
+}
+
+func (ed EfficiencyData) FirstLayer() int {
+	return ed.Layers[0]
+}
+
+func (ed EfficiencyData) SubsequentLayers() []int {
+	return ed.Layers[1:]
 }
 
 // EfficiencySlice represents an ordered set of EfficiencyData data structures.
@@ -42,15 +51,22 @@ func Efficiency(trees []*FileTree) (float64, EfficiencySlice) {
 
 	visitor := func(node *FileNode) error {
 		path := node.Path()
+		first := false
 		if _, ok := efficiencyMap[path]; !ok {
 			efficiencyMap[path] = &EfficiencyData{
 				Path:              path,
 				Nodes:             make([]*FileNode, 0),
 				minDiscoveredSize: -1,
+				Layers:            []int{currentTree},
 			}
+			first = true
 		}
 		data := efficiencyMap[path]
 
+		if !first {
+			data.Layers = append(data.Layers, currentTree)
+		}
+
 		// this node may have had children that were deleted, however, we won't explicitly list out every child, only
 		// the top-most parent with the cumulative size. These operations will need to be done on the full (stacked)
 		// tree.

dive/filetree/efficiency_test.go

@@ -1,6 +1,7 @@
 package filetree
 
 import (
+	"reflect"
 	"testing"
 )
 
@@ -32,7 +33,11 @@ func TestEfficency(t *testing.T) {
 
 	var expectedScore = 0.75
 	var expectedMatches = EfficiencySlice{
-		&EfficiencyData{Path: "/etc/nginx/nginx.conf", CumulativeSize: 7000},
+		&EfficiencyData{
+			Path:           "/etc/nginx/nginx.conf",
+			CumulativeSize: 7000,
+			Layers:         []int{0, 1},
+		},
 	}
 	actualScore, actualMatches := Efficiency(trees)
 
@@ -51,6 +56,19 @@ func TestEfficency(t *testing.T) {
 		t.Errorf("Expected path of %s but go %s", expectedMatches[0].Path, actualMatches[0].Path)
 	}
 
+	if !reflect.DeepEqual(expectedMatches[0].Layers, actualMatches[0].Layers) {
+		t.Errorf("Expected layers of %v but got %v", expectedMatches[0].Layers, actualMatches[0].Layers)
+	}
+
+	if actualMatches[0].FirstLayer() != 0 {
+		t.Errorf("expected first layer 0 but got %v", actualMatches[0].FirstLayer())
+	}
+
+	expectedSubsequent := []int{1}
+	if !reflect.DeepEqual(actualMatches[0].SubsequentLayers(), expectedSubsequent) {
+		t.Errorf("expected subsequent layers %v but got %v", expectedSubsequent, actualMatches[0].SubsequentLayers())
+	}
+
 	if expectedMatches[0].CumulativeSize != actualMatches[0].CumulativeSize {
 		t.Errorf("Expected cumulative size of %v but go %v", expectedMatches[0].CumulativeSize, actualMatches[0].CumulativeSize)
 	}