Clean up note reference when deleting a reply

Deleting a reply only removed its own triples, leaving the parent note
still pointing at the now-deleted reply and orphaning any child replies.

DELETE /replies/:id now detaches the reply from every note that
references it, recursively deletes child replies, and returns 404
instead of crashing when the reply does not exist.

Add tests for the note-reference cleanup and the 404 case.

Author: maboukerfa

controllers/replies_controller.rb

@@ -78,8 +78,35 @@ class RepliesController < ApplicationController
     # Delete a reply
     delete '/:replyid' do
       _reply = LinkedData::Models::Notes::Reply.find(params["replyid"]).first
-      _reply.delete
+      error 404, "Reply #{params["replyid"]} not found" if _reply.nil?
+      remove_reply(_reply)
       halt 204
     end
+
+    # Detach the reply from any note that references it and recursively delete
+    # its child replies before deleting the reply itself, so that no dangling
+    # reference to the deleted reply is left behind.
+    def remove_reply(reply)
+      notes_referencing(reply).each do |note|
+        note.reply = note.reply.reject { |r| r.id == reply.id }
+        note.save
+      end
+
+      reply.bring(:children) unless reply.loaded_attributes.include?(:children)
+      reply.children.each { |child| remove_reply(child) }
+
+      reply.delete
+    end
+    
+    def notes_referencing(reply)
+      reply_predicate = LinkedData::Models::Note.attribute_uri(:reply)
+      Goo.sparql_query_client
+         .select(:id).distinct
+         .from(LinkedData::Models::Note.uri_type)
+         .where([:id, reply_predicate, reply.id])
+         .each_solution
+         .map { |sol| LinkedData::Models::Note.find(sol[:id]).include(LinkedData::Models::Note.attributes).first }
+         .compact
+    end
   end
 end

test/controllers/test_replies_controller.rb

@@ -79,4 +79,51 @@ def test_reply_lifecycle
     assert last_response.status == 204
   end
 
+  def test_delete_reply_removes_note_reference
+    note = LinkedData::Models::Note.new({
+      creator: @@user,
+      subject: "Note for delete reference test",
+      body: "Body for delete reference test",
+      relatedOntology: [@@ontology]
+    })
+    note.save
+
+    reply = LinkedData::Models::Notes::Reply.new({
+      creator: @@user,
+      body: "Reply to be deleted"
+    })
+    reply.save
+
+    child = LinkedData::Models::Notes::Reply.new({
+      creator: @@user,
+      body: "Child of the deleted reply",
+      parent: reply
+    })
+    child.save
+
+    note.reply = (note.reply || []).dup.push(reply)
+    note.save
+
+    reply_id = reply.id
+    child_id = child.id
+
+    delete reply_id.to_s
+    assert_equal 204, last_response.status
+
+    # The reply and its child are gone
+    assert_nil LinkedData::Models::Notes::Reply.find(reply_id).first
+    assert_nil LinkedData::Models::Notes::Reply.find(child_id).first
+
+    # The parent note no longer references the deleted reply
+    note_after = LinkedData::Models::Note.find(note.id).include(:reply).first
+    refute_includes (note_after.reply || []).map { |r| r.id }, reply_id
+
+    note_after.delete
+  end
+
+  def test_delete_missing_reply_returns_404
+    delete "/replies/does-not-exist"
+    assert_equal 404, last_response.status
+  end
+
 end