WIP: Resumable downloads implementation with test fixes needed

Co-authored-by: ericcurtin <1694275+ericcurtin@users.noreply.github.com>

Author: Copilot

pkg/distribution/internal/store/blobs.go

@@ -81,6 +81,12 @@ type blob interface {
 // writeLayer writes the layer blob to the store.
 // It returns true when a new blob was created and the blob's DiffID.
 func (s *LocalStore) writeLayer(layer blob, updates chan<- v1.Update) (bool, v1.Hash, error) {
+	// Check if this is a ResumableLayer and use its special download method
+	if resumableLayer, ok := layer.(*ResumableLayer); ok {
+		return resumableLayer.DownloadAndDecompress(updates)
+	}
+
+	// Standard layer download (non-resumable)
 	hash, err := layer.DiffID()
 	if err != nil {
 		return false, v1.Hash{}, fmt.Errorf("get file hash: %w", err)

pkg/distribution/internal/store/resumable.go

@@ -173,21 +173,31 @@ func (rl *ResumableLayer) DownloadAndDecompress(updates chan<- v1.Update) (bool,
 	}
 	defer compressedFile.Close()
 
+	// Try to decompress - if it fails, the data might already be uncompressed
 	gzipReader, err := gzip.NewReader(compressedFile)
+	var reader io.Reader
 	if err != nil {
-		return false, v1.Hash{}, fmt.Errorf("create gzip reader: %w", err)
+		// Data is not gzipped, use it directly
+		// Need to reopen the file since gzip.NewReader consumed some bytes
+		compressedFile.Close()
+		compressedFile, err = os.Open(compressedIncompletePath)
+		if err != nil {
+			return false, v1.Hash{}, fmt.Errorf("reopen for direct read: %w", err)
+		}
+		reader = compressedFile
+	} else {
+		defer gzipReader.Close()
+		reader = gzipReader
 	}
-	defer gzipReader.Close()
 
 	// Wrap with progress if provided
-	var reader io.Reader = gzipReader
 	if updates != nil {
-		reader = progress.NewReader(gzipReader, updates)
+		reader = progress.NewReader(reader, updates)
 	}
 
-	// Write decompressed data
+	// Write data
 	if err := rl.store.WriteBlob(diffID, reader); err != nil {
-		return false, v1.Hash{}, fmt.Errorf("write decompressed: %w", err)
+		return false, v1.Hash{}, fmt.Errorf("write blob: %w", err)
 	}
 
 	// Clean up compressed file