Implemented descriptors and created a test for the open function

Signed-off-by: Domenico Luciani <[email protected]>

pkg/buildpack/flattener.go

@@ -1,16 +1,30 @@
 package buildpack
 
-type Flattener interface {
-	FlatBuildpacks()
+import "io"
+
+type BuildFlattenModule interface {
+	Open() (io.ReadCloser, error)
+	Descriptors() []Descriptor
+}
+
+type buildpacksFlattenerModule struct {
+	descriptors []Descriptor
 }
 
-type BuildpacksFlattener struct {
+func NewBuildpacksFlattenerModule(buildmodules []BuildModule) BuildFlattenModule {
+	var bpFlattenerModule buildpacksFlattenerModule
+
+	for _, module := range buildmodules {
+		bpFlattenerModule.descriptors = append(bpFlattenerModule.descriptors, module.Descriptor())
+	}
+
+	return bpFlattenerModule
 }
 
-func NewBuildpacksFlattener() BuildpacksFlattener {
-	return BuildpacksFlattener{}
+func (bfm buildpacksFlattenerModule) Descriptors() []Descriptor {
+	return bfm.descriptors
 }
 
-func (bp BuildpacksFlattener) FlatBuildpacks(bps []BuildModule) []BuildModule {
-	return bps //TODO: Implementation
+func (bfm buildpacksFlattenerModule) Open() (io.ReadCloser, error) {
+	return nil, nil
 }

pkg/buildpack/flattener_test.go

@@ -1,6 +1,10 @@
 package buildpack_test
 
 import (
+	"github.com/buildpacks/pack/pkg/archive"
+	"io"
+	"os"
+	"path/filepath"
 	"testing"
 
 	"github.com/buildpacks/lifecycle/api"
@@ -21,7 +25,6 @@ func testFlattener(t *testing.T, when spec.G, it spec.S) {
 	var (
 		bp1 buildpack.BuildModule
 		bp2 buildpack.BuildModule
-		bp3 buildpack.BuildModule
 		err error
 	)
 
@@ -43,28 +46,66 @@ func testFlattener(t *testing.T, when spec.G, it spec.S) {
 			},
 		}, 0644)
 		h.AssertNil(t, err)
-
-		bp3, err = ifakes.NewFakeBuildpack(dist.BuildpackDescriptor{
-			WithAPI: api.MustParse("0.2"),
-			WithInfo: dist.ModuleInfo{
-				ID:      "buildpack-3-id",
-				Version: "buildpack-3-version",
-			},
-		}, 0644)
-		h.AssertNil(t, err)
 	})
 
-	when("Flattener has been called", func() {
-		var (
-			flattener buildpack.BuildpacksFlattener
-		)
-		it.Before(func() {
-			flattener = buildpack.NewBuildpacksFlattener()
+	when("Create a NewBuildpackFlattenModule", func() {
+		it("creates a buildpackFlattenModule with the correct information", func() {
+			buildpackFlattenerModule := buildpack.NewBuildpacksFlattenerModule([]buildpack.BuildModule{bp1, bp2})
+
+			h.AssertEq(t, len(buildpackFlattenerModule.Descriptors()), 2)
 		})
+	})
+
+	when("Open is called", func() {
+		var writeBlobToFile = func(bp buildpack.BuildFlattenModule) string {
+			t.Helper()
+
+			bpReader, err := bp.Open()
+			h.AssertNil(t, err)
+
+			tmpDir, err := os.MkdirTemp("", "")
+			h.AssertNil(t, err)
 
-		it("flats the buildpacks that has been passed", func() {
-			bps := flattener.FlatBuildpacks([]buildpack.BuildModule{bp1, bp2, bp3})
-			h.AssertEq(t, len(bps), 1)
+			p := filepath.Join(tmpDir, "bp.tar")
+			bpWriter, err := os.Create(p)
+			h.AssertNil(t, err)
+
+			_, err = io.Copy(bpWriter, bpReader)
+			h.AssertNil(t, err)
+
+			err = bpReader.Close()
+			h.AssertNil(t, err)
+
+			return p
+		}
+
+		it("Returns the reader about the content of any flatten buildpack", func() {
+			buildpackFlattenerModule := buildpack.NewBuildpacksFlattenerModule([]buildpack.BuildModule{bp1, bp2})
+
+			tarPath := writeBlobToFile(buildpackFlattenerModule)
+
+			assertDirExists(t, tarPath, "/cnb/buildpacks/buildpack-1-id")
+			assertDirExists(t, tarPath, "/cnb/buildpacks/buildpack-1-id/buildpack-1-version")
+			assertDirExists(t, tarPath, "/cnb/buildpacks/buildpack-1-id/buildpack-1-version/bin")
+			assertExecutableExists(t, tarPath, "/cnb/buildpacks/buildpack-1-id/buildpack-1-version/bin/build", "build-contents")
+			assertExecutableExists(t, tarPath, "/cnb/buildpacks/buildpack-1-id/buildpack-1-version/bin/detect", "detect-contents")
+			assertExecutableExists(t, tarPath, "/cnb/buildpacks/buildpack-2-id/buildpack-2-version/bin/build", "build-contents")
+			assertExecutableExists(t, tarPath, "/cnb/buildpacks/buildpack-2-id/buildpack-2-version/bin/detect", "detect-contents")
 		})
 	})
 }
+
+func assertExecutableExists(t *testing.T, tarPath, entryPath, content string) {
+	h.AssertOnTarEntry(t, tarPath, entryPath,
+		h.HasFileMode(0755),
+		h.HasModTime(archive.NormalizedDateTime),
+		h.ContentEquals(content))
+}
+
+func assertDirExists(t *testing.T, tarPath string, entryPath string) {
+	h.AssertOnTarEntry(t, tarPath, entryPath,
+		h.IsDirectory(),
+		h.HasFileMode(0755),
+		h.HasModTime(archive.NormalizedDateTime),
+	)
+}