This Spike describes the implementation and changes necessary in order to support a list element as a top-level data node. 

Implementation Proposal

We will be augmenting the existing CPS-Core endpoint /v1/dataspaces/{dataspace-name}/anchors/{anchor-name}/list-nodes?xpath=/

REST Layer

• DataRestController.java
  • Add a check in addListElements to see if the parent xpath is a root path ("/").  If root node, create passed list element as top node. Else add passed list element to parent xpath node.
• DataRestControllerSpec.groovy
  • Add test for scenario above

Service Layer

• CpsDataService.java
  • Overload saveListElements method with implementation for no parentNodeXpath
• CpsDataServiceImpl.java
  • Overload saveListElements method with implementation for no parentNodeXpath
  • buildDataNodes and call new method storeListElements in Persistence Layer

Persistence Layer

• CpsDataPersistenceService.java
  • new method storeListElements
• CpsDataPersistenceServiceImpl.java
  • new method storeListElements, converts datanodes to fragment repository and saves it.

Issues:

Get Datanode only gets the first node of the list element at the top level. Possible solutions:

• Refactor endpoint get node to get node(s) and have it search for parallel nodes.
• Create new endpoint (get root node / get list elements)
• Refactor endpoint so that it functions differently when root xpath is given

Delete Datanode only deletes one node of the list element at the top level

• Refactor to delete all nodes when passed root xpath /

Confirm that we do not want to allow an empty list element as the top level element (would not be a node)