From 0a57c608958491d32365e807f943daa3ea3e3b87 Mon Sep 17 00:00:00 2001
From: Oskari Timperi <oskari.timperi@iki.fi>
Date: Thu, 26 Apr 2018 18:25:57 +0300
Subject: Fixes to FieldMask serialization

Basically just being more strict about the paths than before.
---
 nimpb/wkt/field_mask.nim | 40 +++++++++++++++++++++++++++++++++++++++-
 1 file changed, 39 insertions(+), 1 deletion(-)

diff --git a/nimpb/wkt/field_mask.nim b/nimpb/wkt/field_mask.nim
index fd38cfb..fb8d04f 100644
--- a/nimpb/wkt/field_mask.nim
+++ b/nimpb/wkt/field_mask.nim
@@ -3,5 +3,43 @@ import strutils
 
 include field_mask_pb
 
+const
+    LowerCaseLetters = {'a'..'z'}
+
+proc snakeCaseToCamelCase(s: string): string =
+    # Nimification from https://github.com/google/protobuf/blob/master/src/google/protobuf/util/field_mask_util.cc
+    result = newStringOfCap(len(s))
+
+    var afterUnderscore = false
+
+    for ch in s:
+        if isUpperAscii(ch):
+            raise newException(ValueError, "string not in snake case")
+
+        if afterUnderscore:
+            if ch in LowerCaseLetters:
+                add(result, toUpperAscii(ch))
+                afterUnderscore = false
+            else:
+                raise newException(ValueError, "lower case expected after underscore")
+        elif ch == '_':
+            afterUnderscore = true
+        else:
+            add(result, ch)
+
+    if afterUnderscore:
+        raise newException(ValueError, "trailing underscore")
+
+proc camelCaseToSnakeCase(s: string): string =
+    # TODO
+    result = s
+
 proc toJson*(message: google_protobuf_FieldMask): JsonNode =
-    %join(message.paths, ",")
+    var resultString = ""
+
+    for index, path in message.paths:
+        add(resultString, snakeCaseToCamelCase(path))
+        if index < len(message.paths)-1:
+            add(resultString, ",")
+
+    result = %resultString
-- 
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