From 0d733ce4e2755e1f5bc14839e1e239d97a1f8f24 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Martin=20Wo=CC=88ginger?= <martin.woeginger@gmail.com>
Date: Sun, 29 Dec 2024 17:48:11 +0100
Subject: [PATCH] implement Outline.merge_next_node

---
 lib/radiator/outline.ex                   | 51 +++++++++++++++++++++++
 lib/radiator/outline/command_processor.ex |  7 +---
 lib/radiator/outline/node_repository.ex   |  1 +
 test/radiator/outline_test.exs            | 40 ++++++++++++++++++
 4 files changed, 94 insertions(+), 5 deletions(-)

diff --git a/lib/radiator/outline.ex b/lib/radiator/outline.ex
index b8348081..dd8372ca 100644
--- a/lib/radiator/outline.ex
+++ b/lib/radiator/outline.ex
@@ -16,6 +16,7 @@ defmodule Radiator.Outline do
   @moduledoc """
   The Outline context.
   """
+  import Ecto.Query
 
   alias Radiator.Outline.Node
   alias Radiator.Outline.NodeRepoResult
@@ -346,6 +347,56 @@ defmodule Radiator.Outline do
     {first, last}
   end
 
+  def merge_prev_node(_node_id) do
+    nil
+  end
+
+  def merge_next_node(%Node{} = node) do
+    merge_next_node(node, NodeRepository.get_next_node(node))
+  end
+
+  def merge_next_node(node_id), do: merge_next_node(NodeRepository.get_node!(node_id))
+
+  def merge_next_node(%Node{} = _node, nil), do: {:error, :no_next_node}
+
+  def merge_next_node(
+        %Node{uuid: node_id} = node,
+        %Node{uuid: next_node_id, content: content_of_next_node} = next_node
+      ) do
+    Ecto.Multi.new()
+    |> Ecto.Multi.update_all(
+      :update_childrens,
+      fn _ ->
+        from(n in Node, where: n.parent_id == ^next_node_id, update: [set: [parent_id: ^node_id]])
+      end,
+      []
+    )
+    |> Ecto.Multi.update(:update_content, fn _changes ->
+      Node.update_content_changeset(node, %{content: node.content <> content_of_next_node})
+    end)
+    |> Ecto.Multi.run(:delete_next_node, fn _, _ ->
+      %NodeRepoResult{node: deleted_node, next: updated_next_node} = remove_node(next_node)
+      {:ok, %{deleted_node: deleted_node, updated_next_node: updated_next_node}}
+    end)
+    |> Repo.transaction()
+    |> case do
+      {:ok, result} ->
+        node = result.update_content
+
+        {:ok,
+         %NodeRepoResult{
+           node: result.update_content,
+           old_next: result.delete_next_node.deleted_node,
+           next: result.delete_next_node.updated_next_node,
+           children: NodeRepository.get_all_siblings(node),
+           outline_node_container_id: node.outline_node_container_id
+         }}
+
+      {:error, _tag, error, _others} ->
+        {:error, error}
+    end
+  end
+
   @doc """
   Removes a node from the tree and deletes it from the repository.
   Recursivly deletes all children if there are some.
diff --git a/lib/radiator/outline/command_processor.ex b/lib/radiator/outline/command_processor.ex
index f4c370b8..c7c8b8d5 100644
--- a/lib/radiator/outline/command_processor.ex
+++ b/lib/radiator/outline/command_processor.ex
@@ -167,12 +167,9 @@ defmodule Radiator.Outline.CommandProcessor do
     # delete current node
   end
 
-  defp process_command(%MergeNextNodeCommand{node_id: _node_id} = _command) do
-    # node_id has a next node?
+  defp process_command(%MergeNextNodeCommand{node_id: node_id} = _command) do
+    Outline.merge_next_node(node_id)
 
-    # get content from next node -> append content to current node
-
-    # delete next node
   end
 
   defp handle_insert_node_result(
diff --git a/lib/radiator/outline/node_repository.ex b/lib/radiator/outline/node_repository.ex
index 11777fc4..b3b09a3e 100644
--- a/lib/radiator/outline/node_repository.ex
+++ b/lib/radiator/outline/node_repository.ex
@@ -277,6 +277,7 @@ defmodule Radiator.Outline.NodeRepository do
   end
 
   @doc """
+  TODO wrong name: sibling is "geschwister" in german
   Returns all direct child nodes of a given node.
   ## Examples
         iex> get_all_siblings(%Node{})
diff --git a/test/radiator/outline_test.exs b/test/radiator/outline_test.exs
index 14633611..dd2b8fc4 100644
--- a/test/radiator/outline_test.exs
+++ b/test/radiator/outline_test.exs
@@ -832,6 +832,46 @@ defmodule Radiator.OutlineTest do
     end
   end
 
+  describe "merge_next_node/1" do
+    setup :complex_node_fixture
+
+    test "merges two nodes into one", %{
+      node_2: node_2,
+      node_3: node_3,
+      nested_node_1: nested_node_1,
+      nested_node_2: nested_node_2,
+      node_4: node_4
+    } do
+      {:ok, result} = Outline.merge_next_node(node_2)
+
+      node_2 = Repo.reload!(node_2)
+      node_4 = Repo.reload!(node_4)
+      nested_node_1 = Repo.reload!(nested_node_1)
+      nested_node_2 = Repo.reload!(nested_node_2)
+      assert is_nil(NodeRepository.get_node(node_3.uuid))
+      assert nested_node_2.parent_id == node_2.uuid
+      assert nested_node_1.parent_id == node_2.uuid
+      assert node_4.prev_id == node_2.uuid
+      assert node_2.content == "node_2node_3"
+
+      assert result.node.uuid == node_2.uuid
+      assert result.old_next.uuid == node_3.uuid
+      assert result.next.uuid == node_4.uuid
+      assert Enum.count(result.children) == 2
+    end
+
+    test "ignores command when there is no next node", %{
+      node_6: node_6
+    } do
+      old_content = node_6.content
+      {:error, :no_next_node} = Outline.merge_next_node(node_6)
+      assert is_nil(NodeRepository.get_next_node(node_6))
+      {:error, :no_next_node} = Outline.merge_next_node(node_6)
+      node_6 = Repo.reload!(node_6)
+      assert old_content == node_6.content
+    end
+  end
+
   describe "indent_node/1 - simple context" do
     setup :simple_node_fixture