lib: implement a NewScope to produce scopes from inputs

Signed-off-by: Alfredo Deza <adeza@anchore.com>

imgbom/lib.go

@@ -1,6 +1,8 @@
 package imgbom
 
 import (
+	"fmt"
+
 	"github.com/anchore/imgbom/imgbom/cataloger"
 	"github.com/anchore/imgbom/imgbom/distro"
 	"github.com/anchore/imgbom/imgbom/logger"
@@ -8,6 +10,7 @@ import (
 	"github.com/anchore/imgbom/imgbom/scope"
 	"github.com/anchore/imgbom/internal/bus"
 	"github.com/anchore/imgbom/internal/log"
+	"github.com/anchore/stereoscope"
 	"github.com/anchore/stereoscope/pkg/image"
 	"github.com/wagoodman/go-partybus"
 )
@@ -16,6 +19,42 @@ func IdentifyDistro(s scope.Scope) *distro.Distro {
 	return distro.Identify(s)
 }
 
+// NewScope produces a Scope based on userInput like dir:// or image:tag
+func NewScope(userInput string, o scope.Option) (scope.Scope, func(), error) {
+	protocol := NewProtocol(userInput)
+	log.Debugf("protocol: %+v", protocol)
+
+	switch protocol.Type {
+	case DirProtocol:
+		// populate the scope object for dir
+		s, err := GetScopeFromDir(protocol.Value, o)
+		if err != nil {
+			return scope.Scope{}, func() {}, fmt.Errorf("could not populate scope from path (%s): %w", protocol.Value, err)
+		}
+		return s, func() {}, nil
+
+	case ImageProtocol:
+		log.Infof("Fetching image '%s'", userInput)
+		img, err := stereoscope.GetImage(userInput)
+		cleanup := func() {
+			stereoscope.Cleanup()
+		}
+
+		if err != nil || img == nil {
+			return scope.Scope{}, cleanup, fmt.Errorf("could not fetch image '%s': %w", userInput, err)
+		}
+
+		s, err := GetScopeFromImage(img, o)
+		if err != nil {
+			return scope.Scope{}, cleanup, fmt.Errorf("could not populate scope with image: %w", err)
+		}
+		return s, cleanup, nil
+
+	default:
+		return scope.Scope{}, func() {}, fmt.Errorf("unable to process input for scanning: '%s'", userInput)
+	}
+}
+
 func GetScopeFromDir(d string, o scope.Option) (scope.Scope, error) {
 	return scope.NewScopeFromDir(d, o)
 }