/// <summary>
/// Reads a <see cref="ODataResource"/> or <see cref="ODataResourceSet"/> object.
/// </summary>
/// <param name="reader">The OData reader to read from.</param>
/// <returns>The read resource or resource set.</returns>
public static async Task <ODataItemBase> ReadResourceOrResourceSetAsync(this ODataReader reader)
{
if (reader == null)
{
throw new ArgumentNullException(nameof(reader));
}
ODataItemBase topLevelItem = null;
Stack <ODataItemBase> itemsStack = new Stack <ODataItemBase>();
while (await reader.ReadAsync().ConfigureAwait(false))
{
ReadCollectionItem(reader, itemsStack, ref topLevelItem);
}
Contract.Assert(reader.State == ODataReaderState.Completed, "We should have consumed all of the input by now.");
Contract.Assert(topLevelItem != null, "A top level resource or resource set should have been read by now.");
return(topLevelItem);
}
private static void ReadCollectionItem(ODataReader reader, Stack <ODataItemBase> itemsStack, ref ODataItemBase topLevelItem)
{
switch (reader.State)
{
case ODataReaderState.ResourceStart:
ODataResource resource = (ODataResource)reader.Item;
ODataResourceWrapper resourceWrapper = null;
if (resource != null)
{
resourceWrapper = new ODataResourceWrapper(resource);
}
if (itemsStack.Count == 0)
{
Contract.Assert(resource != null, "The top-level resource can never be null.");
topLevelItem = resourceWrapper;
}
else
{
ODataItemBase parentItem = itemsStack.Peek();
ODataResourceSetWrapper parentResourceSet = parentItem as ODataResourceSetWrapper;
if (parentResourceSet != null)
{
parentResourceSet.Resources.Add(resourceWrapper);
}
else
{
ODataNestedResourceInfoWrapper parentNestedResource = (ODataNestedResourceInfoWrapper)parentItem;
Contract.Assert(parentNestedResource.NestedResourceInfo.IsCollection == false, "Only singleton nested properties can contain resource as their child.");
Contract.Assert(parentNestedResource.NestedItems.Count == 0, "Each nested property can contain only one resource as its direct child.");
parentNestedResource.NestedItems.Add(resourceWrapper);
}
}
itemsStack.Push(resourceWrapper);
break;
case ODataReaderState.ResourceEnd:
Contract.Assert(
itemsStack.Count > 0 && (reader.Item == null || itemsStack.Peek().Item == reader.Item),
"The resource which is ending should be on the top of the items stack.");
itemsStack.Pop();
break;
case ODataReaderState.NestedResourceInfoStart:
ODataNestedResourceInfo nestedResourceInfo = (ODataNestedResourceInfo)reader.Item;
Contract.Assert(nestedResourceInfo != null, "nested resource info should never be null.");
ODataNestedResourceInfoWrapper nestedResourceInfoWrapper = new ODataNestedResourceInfoWrapper(nestedResourceInfo);
Contract.Assert(itemsStack.Count > 0, "nested resource info can't appear as top-level item.");
{
ODataResourceWrapper parentResource = (ODataResourceWrapper)itemsStack.Peek();
parentResource.NestedResourceInfos.Add(nestedResourceInfoWrapper);
}
itemsStack.Push(nestedResourceInfoWrapper);
break;
case ODataReaderState.NestedResourceInfoEnd:
Contract.Assert(itemsStack.Count > 0 && itemsStack.Peek().Item == reader.Item,
"The nested resource info which is ending should be on the top of the items stack.");
itemsStack.Pop();
break;
case ODataReaderState.ResourceSetStart:
ODataResourceSet resourceSet = (ODataResourceSet)reader.Item;
Contract.Assert(resourceSet != null, "ResourceSet should never be null.");
ODataResourceSetWrapper resourceSetWrapper = new ODataResourceSetWrapper(resourceSet);
if (itemsStack.Count > 0)
{
ODataNestedResourceInfoWrapper parentNestedResourceInfo = (ODataNestedResourceInfoWrapper)itemsStack.Peek();
Contract.Assert(parentNestedResourceInfo != null, "this has to be an inner resource set. inner resource sets always have a nested resource info.");
Contract.Assert(parentNestedResourceInfo.NestedResourceInfo.IsCollection == true, "Only collection nested properties can contain resource set as their child.");
parentNestedResourceInfo.NestedItems.Add(resourceSetWrapper);
}
else
{
topLevelItem = resourceSetWrapper;
}
itemsStack.Push(resourceSetWrapper);
break;
case ODataReaderState.ResourceSetEnd:
Contract.Assert(itemsStack.Count > 0 && itemsStack.Peek().Item == reader.Item, "The resource set which is ending should be on the top of the items stack.");
itemsStack.Pop();
break;
case ODataReaderState.EntityReferenceLink:
ODataEntityReferenceLink entityReferenceLink = (ODataEntityReferenceLink)reader.Item;
Contract.Assert(entityReferenceLink != null, "Entity reference link should never be null.");
ODataEntityReferenceLinkBase entityReferenceLinkWrapper = new ODataEntityReferenceLinkBase(entityReferenceLink);
Contract.Assert(itemsStack.Count > 0, "Entity reference link should never be reported as top-level item.");
{
ODataNestedResourceInfoWrapper parentNavigationLink = (ODataNestedResourceInfoWrapper)itemsStack.Peek();
parentNavigationLink.NestedItems.Add(entityReferenceLinkWrapper);
}
break;
default:
Contract.Assert(false, "We should never get here, it means the ODataReader reported a wrong state.");
break;
}
}
