feat(cataloger): add snap package cataloger for metadata extraction (#4151)

---------
Signed-off-by: Alan Pope <alan.pope@anchore.com>
Signed-off-by: Christopher Phillips <32073428+spiffcs@users.noreply.github.com>
Co-authored-by: Christopher Phillips <32073428+spiffcs@users.noreply.github.com>

syft/pkg/cataloger/snap/package.go

@@ -0,0 +1,94 @@
+package snap
+
+import (
+	"github.com/anchore/packageurl-go"
+	"github.com/anchore/syft/syft/file"
+	"github.com/anchore/syft/syft/pkg"
+)
+
+// newPackage creates a new Package from snap metadata
+func newPackage(name, version string, metadata pkg.SnapEntry, locations ...file.Location) pkg.Package {
+	p := pkg.Package{
+		Name:      name,
+		Version:   version,
+		Locations: file.NewLocationSet(locations...),
+		PURL:      packageURL(name, version, metadata),
+		Type:      pkg.DebPkg, // Use Debian package type for compatibility
+		Metadata:  metadata,
+	}
+
+	p.SetID()
+
+	return p
+}
+
+// packageURL returns the PURL for a snap package
+func packageURL(name, version string, metadata pkg.SnapEntry) string {
+	var qualifiers packageurl.Qualifiers
+
+	if metadata.Architecture != "" {
+		qualifiers = append(qualifiers, packageurl.Qualifier{
+			Key:   "arch",
+			Value: metadata.Architecture,
+		})
+	}
+
+	if metadata.Base != "" {
+		qualifiers = append(qualifiers, packageurl.Qualifier{
+			Key:   "base",
+			Value: metadata.Base,
+		})
+	}
+
+	if metadata.SnapType != "" {
+		qualifiers = append(qualifiers, packageurl.Qualifier{
+			Key:   "type",
+			Value: metadata.SnapType,
+		})
+	}
+
+	return packageurl.NewPackageURL(
+		packageurl.TypeGeneric,
+		"snap",
+		name,
+		version,
+		qualifiers,
+		"",
+	).ToString()
+}
+
+// newDebianPackageFromSnap creates a Debian-style package entry from snap manifest data
+func newDebianPackageFromSnap(name, version string, snapMetadata pkg.SnapEntry, locations ...file.Location) pkg.Package {
+	p := pkg.Package{
+		Name:      name,
+		Version:   version,
+		Locations: file.NewLocationSet(locations...),
+		Type:      pkg.DebPkg,
+		PURL:      debianPackageURL(name, version, snapMetadata.Architecture),
+		Metadata:  snapMetadata,
+	}
+
+	p.SetID()
+	return p
+}
+
+// debianPackageURL creates a PURL for Debian packages found in snaps
+func debianPackageURL(name, version, architecture string) string {
+	var qualifiers packageurl.Qualifiers
+
+	if architecture != "" {
+		qualifiers = append(qualifiers, packageurl.Qualifier{
+			Key:   "arch",
+			Value: architecture,
+		})
+	}
+
+	return packageurl.NewPackageURL(
+		packageurl.TypeDebian,
+		"ubuntu", // Assume Ubuntu since most snaps are built on Ubuntu
+		name,
+		version,
+		qualifiers,
+		"",
+	).ToString()
+}