private JsonPlusValue ResolveSubstitution(JsonPlusSubstitution sub)
{
JsonPlusObjectMember subField = sub.ParentMember;
// first case, this substitution is a direct self-reference
if (sub.Path == sub.GetMemberPath())
{
IJsonPlusNode parent = sub.Parent;
while (parent is JsonPlusValue)
{
parent = parent.Parent;
}
// Fail case
if (parent is JsonPlusArray)
{
throw new JsonPlusException(RS.SelfRefSubstitutionInArray);
}
// try to resolve substitution by looking backward in the field assignment stack
return(subField.OlderValueThan(sub));
}
// need to recursively get full path
JsonPlusPath fieldPath = subField.GetMemberPath();
// second case, the substitution references a field child in the past
if (sub.Path.IsChildPathOf(fieldPath))
{
JsonPlusValue olderValue = subField.OlderValueThan(sub);
if ((olderValue != null) &&
(olderValue.Type == JsonPlusType.Object))
{
int difLength = sub.Path.Count - fieldPath.Count;
JsonPlusPath deltaPath = sub.Path.SubPath(sub.Path.Count - difLength, difLength);
JsonPlusObject olderObject = olderValue.GetObject();
if (olderObject.TryGetValue(deltaPath, out JsonPlusValue innerValue))
{
return(innerValue.Type == JsonPlusType.Object ? innerValue : null);
}
}
}
// Detect invalid parent-referencing substitution
if (fieldPath.IsChildPathOf(sub.Path))
{
throw new JsonPlusException(RS.SubstitutionRefDirectParentError);
}
// Detect invalid cyclic reference loop
if (IsValueCyclic(subField, sub))
{
throw new JsonPlusException(RS.CyclicSubstitutionLoop);
}
// third case, regular substitution
_root.GetObject().TryGetValue(sub.Path, out JsonPlusValue field);
return(field);
}
internal JsonPlusValue OlderValueThan(IJsonPlusNode marker)
{
List <JsonPlusObject> objectList = new List <JsonPlusObject>();
int index = 0;
while (index < _internalValues.Count)
{
JsonPlusValue value = _internalValues[index];
if (value.Any(v => ReferenceEquals(v, marker)))
{
break;
}
switch (value.Type)
{
case JsonPlusType.Object:
objectList.Add(value.GetObject());
break;
case JsonPlusType.Literal:
case JsonPlusType.Array:
objectList.Clear();
break;
}
index++;
}
if (objectList.Count == 0)
{
return(index == 0
? null
: _internalValues[index - 1]);
}
JsonPlusValue result = new JsonPlusValue(null);
JsonPlusObject o = new JsonPlusObject(result);
result.Add(o);
foreach (JsonPlusObject obj in objectList)
{
o.Merge(obj);
}
return(result);
}