/// <summary>
/// Expands a node into child nodes.
/// </summary>
/// <param name="node">The node to expand</param>
/// <param name="model">The ODCM model</param>
/// <returns>The child nodes if the node can be expanded, otherwise an empty list.</returns>
private static IEnumerable <OdcmNode> CreateChildNodes(this OdcmNode node, OdcmModel model)
{
if (node == null)
{
throw new ArgumentNullException(nameof(node));
}
if (model == null)
{
throw new ArgumentNullException(nameof(model));
}
// Identify the kind of ODCM element this node represents and expand it if we need to
OdcmProperty obj = node.OdcmProperty;
IEnumerable <OdcmProperty> childObjects = obj.Type.GetChildObjects(model);
// Don't allow loops in the list of ODCM nodes
ICollection <string> parents = new HashSet <string>();
OdcmNode currentNode = node;
while (currentNode != null)
{
parents.Add(currentNode.OdcmProperty.CanonicalName());
currentNode = currentNode.Parent;
}
return(childObjects
// Filter out the children we've already seen so we can avoid loops
.Where(child => !parents.Contains(child.CanonicalName()))
// Add the child nodes to the current node
.Select(child => node.CreateChildNode(child)));
}
/// <summary>
/// Converts the structure of an ODCM model into a tree and returns all of the nodes in the tree.
/// The first node returned is guaranteed to be the root of the tree, however the order of the remaining nodes is undetermined.
/// </summary>
/// <param name="obj">The ODCM model to convert</param>
/// <returns>The root node of the created tree.</returns>
public static IEnumerable <OdcmNode> ConvertToOdcmNodes(this OdcmModel model)
{
if (model == null)
{
throw new ArgumentNullException(nameof(model));
}
// Create a stack to allow us to traverse the model
Stack <OdcmNode> unvisited = new Stack <OdcmNode>();
// The EntityContainer in the model represents all of the data exposed through the OData service
OdcmClass entityContainer = model.EntityContainer;
// Evaluate the EntityContainer's children
foreach (OdcmProperty prop in entityContainer.GetChildObjects(model))
{
// Mark the EntityContainer's properties as "to be expanded" if it is not a "$ref" property
unvisited.Push(new OdcmNode(prop));
}
// Continue adding to the tree until there are no more nodes to expand
while (unvisited.Any())
{
// Get the next node to expand
OdcmNode currentNode = unvisited.Pop();
// Return the visited node so it can be processed immediately
yield return(currentNode);
// Mark the child nodes as "to be expanded" if we haven't hit the maximum traversal depth and it is not a reference property
int currentDepth = new ODataRoute(currentNode).Segments.Count;
if (currentDepth <= MaxTraversalDepth && !currentNode.OdcmProperty.IsReference(currentNode.Parent?.OdcmProperty))
{
// Expand the node
IEnumerable <OdcmNode> childNodes = currentNode.CreateChildNodes(model);
// Mark the child nodes as "to be expanded"
foreach (OdcmNode childNode in childNodes)
{
unvisited.Push(childNode);
}
}
}
}
