1 files changed, 34 insertions, 0 deletions
diff --git a/skate/map.go b/skate/map.go
index b647480..17d9ed2 100644
--- a/skate/map.go
+++ b/skate/map.go
@@ -278,6 +278,40 @@ func MapperReleaseResolvedContainerName(p []byte) (fields [][]byte, err error) {
 	return [][]byte{key, p}, nil
 }
 
+func MapperOpenLibraryReleaseNormalizedISBN(p []byte) (fields [][]byte, err error) {
+	var (
+		doc    Release
+		key    []byte
+		isbn13 string
+	)
+	if err := json.Unmarshal(p, &doc); err != nil {
+		return nil, err
+	}
+	// There can be 10 and 13 variants in the data, we always want 13.
+	for _, isbn := range doc.ExtIDs.ISBN {
+		if len(isbn) == 13 {
+			isbn13 = isbn
+			break
+		}
+	}
+	if isbn13 == "" {
+		// This is rarer, more expensive.
+		for _, isbn := range doc.ExtIDs.ISBN {
+			parsed := ParseIsbn(isbn)
+			if len(parsed) > 0 {
+				isbn13 = parsed[0]
+				break
+			}
+		}
+	}
+	if isbn13 == "" {
+		return nil, nil
+	} else {
+		key = []byte(isbn13)
+	}
+	return [][]byte{key, p}, nil
+}
+
 // MapperPartial works on partial documents.
 func MapperPartial(p []byte) (fields [][]byte, err error) {
 	// TODO: Group by some normlized container name or identifier.