Add source bundle validation and inspection

internal/bundle/discover.go

@@ -0,0 +1,82 @@
+package bundle
+
+import (
+	"context"
+	"fmt"
+	"path"
+	"sort"
+	"strings"
+
+	"gitea.maximumdirect.net/eric/distributor/internal/storage"
+)
+
+func Discover(ctx context.Context, backend storage.Backend, sourceRoot string) ([]Bundle, error) {
+	if err := storage.ValidatePrefix(sourceRoot); err != nil {
+		return nil, err
+	}
+	entries, err := storage.List(ctx, backend, sourceRoot, storage.WalkOptions{Recursive: true})
+	if err != nil {
+		return nil, err
+	}
+
+	var roots []string
+	for _, entry := range entries {
+		if entry.Type == storage.EntryTypeDirectory {
+			continue
+		}
+		if path.Base(entry.Path) == ManifestName {
+			roots = append(roots, path.Dir(entry.Path))
+		}
+	}
+	for index, root := range roots {
+		if root == "." {
+			roots[index] = ""
+		}
+	}
+	sort.Strings(roots)
+	if len(roots) == 0 {
+		return nil, fmt.Errorf("no bundles found under %q", displayRoot(sourceRoot))
+	}
+	if err := rejectNestedRoots(roots); err != nil {
+		return nil, err
+	}
+
+	bundles := make([]Bundle, 0, len(roots))
+	for _, root := range roots {
+		relativeRoot := relativeToSource(sourceRoot, root)
+		sourceBundle, err := validateAt(ctx, backend, root, relativeRoot)
+		if err != nil {
+			return nil, err
+		}
+		bundles = append(bundles, sourceBundle)
+	}
+	return bundles, nil
+}
+
+func rejectNestedRoots(roots []string) error {
+	for index, root := range roots {
+		for _, candidate := range roots[index+1:] {
+			if isAncestor(root, candidate) {
+				return fmt.Errorf("nested manifest %q under bundle %q", displayRoot(candidate), displayRoot(root))
+			}
+		}
+	}
+	return nil
+}
+
+func isAncestor(root, candidate string) bool {
+	if root == "" {
+		return candidate != ""
+	}
+	return strings.HasPrefix(candidate, root+"/")
+}
+
+func relativeToSource(sourceRoot, bundleRoot string) string {
+	if sourceRoot == "" {
+		return bundleRoot
+	}
+	if bundleRoot == sourceRoot {
+		return ""
+	}
+	return strings.TrimPrefix(bundleRoot, sourceRoot+"/")
+}