Drain pkg/transformers.

api/transform/mutatefield.go

@@ -0,0 +1,77 @@
+// Copyright 2019 The Kubernetes Authors.
+// SPDX-License-Identifier: Apache-2.0
+
+package transform
+
+import (
+	"fmt"
+	"log"
+	"strings"
+)
+
+type mutateFunc func(interface{}) (interface{}, error)
+
+func MutateField(
+	m map[string]interface{},
+	pathToField []string,
+	createIfNotPresent bool,
+	fns ...mutateFunc) error {
+	if len(pathToField) == 0 {
+		return nil
+	}
+
+	firstPathSegment, isArray := getFirstPathSegment(pathToField)
+
+	_, found := m[firstPathSegment]
+	if !found {
+		if !createIfNotPresent || isArray {
+			return nil
+		}
+		m[firstPathSegment] = map[string]interface{}{}
+	}
+
+	if len(pathToField) == 1 {
+		var err error
+		for _, fn := range fns {
+			m[firstPathSegment], err = fn(m[firstPathSegment])
+			if err != nil {
+				return err
+			}
+		}
+		return nil
+	}
+
+	v := m[firstPathSegment]
+	newPathToField := pathToField[1:]
+	switch typedV := v.(type) {
+	case nil:
+		log.Printf(
+			"nil value at `%s` ignored in mutation attempt",
+			strings.Join(pathToField, "."))
+		return nil
+	case map[string]interface{}:
+		return MutateField(typedV, newPathToField, createIfNotPresent, fns...)
+	case []interface{}:
+		for i := range typedV {
+			item := typedV[i]
+			typedItem, ok := item.(map[string]interface{})
+			if !ok {
+				return fmt.Errorf("%#v is expected to be %T", item, typedItem)
+			}
+			err := MutateField(typedItem, newPathToField, createIfNotPresent, fns...)
+			if err != nil {
+				return err
+			}
+		}
+		return nil
+	default:
+		return fmt.Errorf("%#v is not expected to be a primitive type", typedV)
+	}
+}
+
+func getFirstPathSegment(pathToField []string) (string, bool) {
+	if strings.HasSuffix(pathToField[0], "[]") {
+		return pathToField[0][:len(pathToField[0])-2], true
+	}
+	return pathToField[0], false
+}