Add accessors to Hash and Verify artifacts

Refers to #28

pkg/compiler/artifact.go

@@ -55,7 +55,7 @@ type PackageArtifact struct {
 	Path            string                    `json:"path"`
 	Dependencies    []*PackageArtifact        `json:"dependencies"`
 	CompileSpec     *LuetCompilationSpec      `json:"compilationspec"`
-
+	Checksums       Checksums                 `json:"checksums"`
 	SourceAssertion solver.PackagesAssertions `json:"-"`
 }
 
@@ -64,7 +64,7 @@ func NewPackageArtifact(path string) Artifact {
 }
 
 func NewPackageArtifactFromYaml(data []byte) (Artifact, error) {
-	p := &PackageArtifact{}
+	p := &PackageArtifact{Checksums: Checksums{}}
 	err := yaml.Unmarshal(data, &p)
 	if err != nil {
 		return p, err
@@ -73,7 +73,30 @@ func NewPackageArtifactFromYaml(data []byte) (Artifact, error) {
 	return p, err
 }
 
+func (a *PackageArtifact) Hash() error {
+	return a.Checksums.Generate(a)
+}
+
+func (a *PackageArtifact) Verify() error {
+	sum := Checksums{}
+	err := sum.Generate(a)
+	if err != nil {
+		return err
+	}
+	err = sum.Compare(a.Checksums)
+	if err != nil {
+		return err
+	}
+	return nil
+}
+
 func (a *PackageArtifact) WriteYaml(dst string) error {
+	// First compute checksum of artifact. When we write the yaml we want to write up-to-date informations.
+	err := a.Hash()
+	if err != nil {
+		return errors.Wrap(err, "Failed generating checksums for artifact")
+	}
+
 	//p := a.CompileSpec.GetPackage().GetPath()
 
 	//a.CompileSpec.GetPackage().SetPath("")

pkg/compiler/interface.go

@@ -65,6 +65,8 @@ type Artifact interface {
 	Unpack(dst string, keepPerms bool) error
 	Compress(src string) error
 	FileList() ([]string, error)
+	Hash() error
+	Verify() error
 }
 
 type ArtifactNode struct {