support multiple index values for a single object

pkg/client/cache/index.go

@@ -30,18 +30,36 @@ type Indexer interface {
 	Index(indexName string, obj interface{}) ([]interface{}, error)
 	// ListIndexFuncValues returns the list of generated values of an Index func
 	ListIndexFuncValues(indexName string) []string
+	// ByIndex lists object that match on the named indexing function with the exact key
+	ByIndex(indexName, indexKey string) ([]interface{}, error)
 }
 
 // IndexFunc knows how to provide an indexed value for an object.
-type IndexFunc func(obj interface{}) (string, error)
+type IndexFunc func(obj interface{}) ([]string, error)
+
+// IndexFuncToKeyFuncAdapter adapts an indexFunc to a keyFunc.  This is only useful if your index function returns
+// unique values for every object.  This is conversion can create errors when more than one key is found.  You
+// should prefer to make proper key and index functions.
+func IndexFuncToKeyFuncAdapter(indexFunc IndexFunc) KeyFunc {
+	return func(obj interface{}) (string, error) {
+		indexKeys, err := indexFunc(obj)
+		if err != nil {
+			return "", err
+		}
+		if len(indexKeys) > 1 {
+			return "", fmt.Errorf("too many keys: %v", indexKeys)
+		}
+		return indexKeys[0], nil
+	}
+}
 
 // MetaNamespaceIndexFunc is a default index function that indexes based on an object's namespace
-func MetaNamespaceIndexFunc(obj interface{}) (string, error) {
+func MetaNamespaceIndexFunc(obj interface{}) ([]string, error) {
 	meta, err := meta.Accessor(obj)
 	if err != nil {
-		return "", fmt.Errorf("object has no meta: %v", err)
+		return []string{""}, fmt.Errorf("object has no meta: %v", err)
 	}
-	return meta.Namespace(), nil
+	return []string{meta.Namespace()}, nil
 }
 
 // Index maps the indexed value to a set of keys in the store that match on that value