public Exceptional<TypeAttribute> CreateBackwardEdgeAttribute(BackwardEdgeDefinition myBackwardEdgeNode, GraphDBType myDBTypeStream, UInt16 beAttrCounter = 0)
{
var edgeType = GetTypeByName(myBackwardEdgeNode.TypeName);
if (edgeType == null)
return new Exceptional<TypeAttribute>(new Error_TypeDoesNotExist(myBackwardEdgeNode.TypeName));
var edgeAttribute = edgeType.GetTypeAttributeByName(myBackwardEdgeNode.TypeAttributeName);
//error if the attribute does not exist
#region
if (edgeAttribute == null)
{
return new Exceptional<TypeAttribute>(new Error_AttributeIsNotDefined(edgeType.Name, myBackwardEdgeNode.TypeAttributeName));
}
#endregion
//error if the attribute does not represent non userdefined content
#region
if (!edgeAttribute.GetDBType(this).IsUserDefined)
{
return new Exceptional<TypeAttribute>(new Error_BackwardEdgesForNotReferenceAttributeTypesAreNotAllowed(myBackwardEdgeNode.TypeAttributeName));
}
#endregion
//invalid backwardEdge destination
#region
if (edgeAttribute.GetDBType(this) != myDBTypeStream)
return new Exceptional<TypeAttribute>(new Error_BackwardEdgeDestinationIsInvalid(myDBTypeStream.Name, myBackwardEdgeNode.TypeAttributeName));
#endregion
//error if there is already an be attribute on the to be changed type that points to the same destination
#region
var edgeKey = new EdgeKey(edgeType.UUID, edgeAttribute.UUID);
if (myDBTypeStream.Attributes.Exists(aKV => aKV.Value.IsBackwardEdge && (aKV.Value.BackwardEdgeDefinition == edgeKey)))
{
return new Exceptional<TypeAttribute>(new Error_BackwardEdgeAlreadyExist(myDBTypeStream, edgeType.Name, edgeAttribute.Name));
}
#endregion
//error if the backwardEdge points to a backward edge
#region
var beDestinationAttribute = edgeKey.GetTypeAndAttributeInformation(this).Item2;
if (beDestinationAttribute.IsBackwardEdge)
return new Exceptional<TypeAttribute>(new Error_BackwardEdgeAlreadyExist(myDBTypeStream, edgeType.Name, edgeAttribute.Name));
#endregion
var ta = new TypeAttribute(Convert.ToUInt16(beAttrCounter + DBConstants.DefaultBackwardEdgeIDStart));
ta.DBTypeUUID = DBBackwardEdgeType.UUID;
ta.BackwardEdgeDefinition = edgeKey;
ta.KindOfType = KindsOfType.SetOfReferences;
ta.Name = myBackwardEdgeNode.AttributeName;
ta.EdgeType = myBackwardEdgeNode.EdgeType.GetNewInstance();
ta.TypeCharacteristics.IsBackwardEdge = true;
ta.RelatedGraphDBTypeUUID = myDBTypeStream.UUID;
return new Exceptional<TypeAttribute>(ta);
}
