1 files changed, 58 insertions, 0 deletions
diff --git a/parser/lowercase_camel_json.go b/parser/lowercase_camel_json.go
new file mode 100644
index 000000000..6994d1215
--- /dev/null
+++ b/parser/lowercase_camel_json.go
@@ -0,0 +1,58 @@
+// Copyright 2019 The Hugo Authors. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package parser
+
+import (
+	"bytes"
+	"encoding/json"
+	"regexp"
+	"unicode"
+	"unicode/utf8"
+)
+
+// Regexp definitions
+var keyMatchRegex = regexp.MustCompile(`\"(\w+)\":`)
+var wordBarrierRegex = regexp.MustCompile(`(\w)([A-Z])`)
+
+// Code adapted from https://gist.github.com/piersy/b9934790a8892db1a603820c0c23e4a7
+type LowerCaseCamelJSONMarshaller struct {
+	Value interface{}
+}
+
+func (c LowerCaseCamelJSONMarshaller) MarshalJSON() ([]byte, error) {
+	marshalled, err := json.Marshal(c.Value)
+
+	converted := keyMatchRegex.ReplaceAllFunc(
+		marshalled,
+		func(match []byte) []byte {
+
+			// Attributes on the form XML, JSON etc.
+			if bytes.Equal(match, bytes.ToUpper(match)) {
+				return bytes.ToLower(match)
+			}
+
+			// Empty keys are valid JSON, only lowercase if we do not have an
+			// empty key.
+			if len(match) > 2 {
+				// Decode first rune after the double quotes
+				r, width := utf8.DecodeRune(match[1:])
+				r = unicode.ToLower(r)
+				utf8.EncodeRune(match[1:width+1], r)
+			}
+			return match
+		},
+	)
+
+	return converted, err
+}