proceed with validations

lib/radiator/outline/validations.ex

@@ -3,6 +3,7 @@ defmodule Radiator.Outline.Validations do
     Collection of consistency validations for the outline tree.
   """
   alias Radiator.Outline
+  alias Radiator.Outline.Node
   alias Radiator.Outline.NodeRepository
 
   def validate_consistency_for_move(
@@ -44,9 +45,25 @@ defmodule Radiator.Outline.Validations do
     # every level has 1 node with prev_id nil
     # all other nodes in level have prev_id set and are connected to the previous node
     if Enum.count(tree_nodes) == NodeRepository.count_nodes_by_episode(episode_id) do
+      # iterate through the levels of the tree
+      tree_nodes
+      |> Enum.group_by(& &1.level)
+      |> Enum.map(fn {_level, nodes} ->
+        # get the node with prev_id nil
+        first_node = Enum.find(nodes, & &1.prev_id == nil)
+        # get the rest of the nodes
+        rest_nodes = Enum.reject(nodes, & &1.prev_id == nil)
+        # iterate through the rest of the nodes
+        Enum.reduce(rest_nodes, first_node, fn node, prev_node ->
+          is_node_prev_node_of(prev_node, node)
+        end)
+      end)
       {:ok}
     else
       {:error, :node_count_not_consistent}
     end
   end
+
+  def is_node_prev_node_of(%Radiator.Outline.Node{uuid: id}, %Radiator.Outline.Node{prev_id: id} = node), do: node
+  def is_node_prev_node_of(_, _), do: {:error, :prev_id_not_consistent}
 end

test/radiator/outline/validations_test.exs

@@ -0,0 +1,5 @@
+defmodule Radiator.Outline.ValidationsTest do
+  @moduledoc false
+
+  use Radiator.DataCase
+end