Record the full lifecycle contract in NodeAction entries

A contract comment above NodeAction.record! now specifies every
verb's metadata shape. NodeAction.head_diff computes the publish
diff between an outgoing head and its replacement -- default-locale
title pair always, author/tags pairs and template/assets/abstract/
body flags only when changed, and a per-locale translation_diff
with added/removed/changed status. It is a pure function of its two
pages, shared by publish, rollback, and the future backfill, and
reads translation rows directly so fallbacks never masquerade as
content.

publish entries carry via ("draft" or "revision"); restore_revision!
is now transactional, takes the acting user, and logs through the
same diff. Staged slug/parent changes applied at publish log a move
entry with the path pair. Node creation logs a create entry with
initial title and path. The draft-scoped translation_destroy writer
is retired -- locale removal is recorded by the publish diff, where
it becomes public fact.

2 files changed, 172 insertions, 3 deletions

diff --git a/test/models/node_action_test.rb b/test/models/node_action_test.rb
new file mode 100644
index 0000000..24d8245
--- /dev/null
+++ b/test/models/node_action_test.rb
@@ -0,0 +1,112 @@
+require "test_helper"
+
+class NodeActionTest < ActiveSupport::TestCase
+
+  # Standalone pages, no node -- same pattern autosave relies on.
+  # Default-locale attributes are written pinned, never ambient.
+  def build_page en: nil, **attrs
+    page = Globalize.with_locale(I18n.default_locale) do
+      Page.create!({ :title => "Titel" }.merge(attrs))
+    end
+    page.translations.create!({ :locale => "en" }.merge(en)) if en
+    page.reload
+  end
+
+  test "first publish yields exactly the title pair, from nil" do
+    diff = NodeAction.head_diff(nil, build_page(:title => "Erstausgabe"))
+
+    assert_equal({ :title => { "from" => nil, "to" => "Erstausgabe" } }, diff)
+  end
+
+  test "title pair is always present, even when unchanged" do
+    diff = NodeAction.head_diff(build_page, build_page)
+
+    assert_equal "Titel", diff[:title]["from"]
+    assert_equal "Titel", diff[:title]["to"]
+  end
+
+  test "author pair present only when the byline changed" do
+    u1, u2 = users(:quentin), users(:aaron)
+
+    assert_nil NodeAction.head_diff(build_page(:user => u1), build_page(:user => u1))[:author]
+
+    changed = NodeAction.head_diff(build_page(:user => u1), build_page(:user => u2))
+    assert_equal({ "from" => u1.login, "to" => u2.login }, changed[:author])
+  end
+
+  test "tags pair present only when the tag set changed" do
+    old_page = build_page; old_page.tag_list = "alpha, beta";  old_page.save!
+    new_page = build_page; new_page.tag_list = "beta, gamma"; new_page.save!
+
+    diff = NodeAction.head_diff(old_page.reload, new_page.reload)
+    assert_equal %w[alpha beta],  diff[:tags]["from"]
+    assert_equal %w[beta gamma], diff[:tags]["to"]
+
+    same = NodeAction.head_diff(old_page, old_page)
+    assert_nil same[:tags]
+  end
+
+  test "template_changed flag only when true" do
+    old_page = build_page(:template_name => "standard_template")
+
+    assert NodeAction.head_diff(old_page, build_page(:template_name => "update"))[:template_changed]
+    assert_nil NodeAction.head_diff(old_page, build_page(:template_name => "standard_template"))[:template_changed]
+  end
+
+  test "assets_changed flag when the attached set differs" do
+    asset = Asset.create!(:name => "diff probe",
+                          :upload_file_name    => "test_image.png",
+                          :upload_content_type => "image/png",
+                          :upload_file_size    => 49854,
+                          :upload_updated_at   => Time.current)
+    old_page, new_page = build_page, build_page
+    new_page.related_assets.create!(:asset_id => asset.id, :position => 1)
+
+
+    diff = NodeAction.head_diff(old_page, new_page.reload)
+    assert diff[:assets_changed]
+    assert_nil NodeAction.head_diff(old_page, old_page)[:assets_changed]
+  end
+
+  test "default-locale abstract and body changes become flags, only when true" do
+    diff = NodeAction.head_diff(build_page(:abstract => "a"), build_page(:abstract => "b"))
+
+    assert diff[:abstract_changed]
+    assert_nil diff[:body_changed]
+  end
+
+  test "added locale carries status and the new title" do
+    diff = NodeAction.head_diff(build_page, build_page(en: { :title => "English" }))
+
+    entry = diff[:translation_diff]["en"]
+    assert_equal "added", entry["status"]
+    assert_equal({ "from" => nil, "to" => "English" }, entry["title"])
+  end
+
+  test "removed locale keeps the vanished title" do
+    diff = NodeAction.head_diff(build_page(en: { :title => "English" }), build_page)
+
+    entry = diff[:translation_diff]["en"]
+    assert_equal "removed", entry["status"]
+    assert_equal "English", entry["title"]["from"]
+    assert_nil entry["title"]["to"]
+  end
+
+  test "changed locale carries only what actually differs" do
+    old_page = build_page(en: { :title => "Same", :body => "old" })
+    new_page = build_page(en: { :title => "Same", :body => "new" })
+
+    entry = NodeAction.head_diff(old_page, new_page)[:translation_diff]["en"]
+    assert_equal "changed", entry["status"]
+    assert_nil entry["title"]
+    assert entry["body_changed"]
+    assert_nil entry["abstract_changed"]
+  end
+
+  test "untouched locales are absent; identical pages yield no translation_diff at all" do
+    old_page = build_page(en: { :title => "Same" })
+    new_page = build_page(en: { :title => "Same" })
+
+    assert_nil NodeAction.head_diff(old_page, new_page)[:translation_diff]
+  end
+end
diff --git a/test/models/node_test.rb b/test/models/node_test.rb
index 022fff6..c8e49e5 100644
--- a/test/models/node_test.rb
+++ b/test/models/node_test.rb
@@ -633,6 +633,7 @@ class NodeTest < ActiveSupport::TestCase
     assert_equal node.head, action.page
     assert_equal @user1, action.user
     assert_equal "publish", action.action
+    assert_equal "draft", action.metadata["via"]
   end
 
   test "publish_draft! called with no user logs no actor, not a guessed one" do
@@ -692,7 +693,7 @@ class NodeTest < ActiveSupport::TestCase
     assert_equal count_before, NodeAction.count
   end
 
-  test "publish_draft! records the title's from/to in metadata" do
+  test "publish_draft! records the title diff in metadata" do
     node = create_node_with_published_page
     Globalize.with_locale(:de) { node.head.update!(:title => "Original Title") }
     find_or_create_draft(node, @user1)
@@ -701,7 +702,63 @@ class NodeTest < ActiveSupport::TestCase
     node.publish_draft!(@user1)
 
     action = NodeAction.last
-    assert_equal "Original Title", action.metadata["from"]
-    assert_equal "New Title", action.metadata["to"]
+    assert_equal "draft",          action.metadata["via"]
+    assert_equal "Original Title", action.metadata.dig("title", "from")
+    assert_equal "New Title",      action.metadata.dig("title", "to")
+  end
+
+  test "publishing a staged slug change logs a move with the path pair" do
+    node = create_node_with_published_page
+    path_before = node.unique_name
+    node.staged_slug = "moved-#{node.slug}"
+    node.save!
+    publish_count_before = NodeAction.where(:action => "publish").count
+
+    node.publish_draft!(@user1)
+
+    node.reload
+    assert_not_equal path_before, node.unique_name
+
+    action = NodeAction.where(:action => "move").last
+    assert_equal node,             action.node
+    assert_equal @user1,           action.user
+    assert_equal path_before,      action.metadata.dig("path", "from")
+    assert_equal node.unique_name, action.metadata.dig("path", "to")
+
+    # No draft was pending: path change alone must not fabricate a publish.
+    assert_equal publish_count_before, NodeAction.where(:action => "publish").count
+  end
+
+  test "publishing a draft together with a staged move logs two entries" do
+    node = create_node_with_published_page
+    find_or_create_draft(node, @user1)
+    node.staged_slug = "relocated-#{node.slug}"
+    node.save!
+
+    assert_difference "NodeAction.count", 2 do
+      node.publish_draft!(@user1)
+    end
+
+    assert_equal %w[move publish],
+                 NodeAction.order(:id).last(2).map(&:action).sort
+  end
+
+  test "restore_revision! logs a publish via revision" do
+    node = create_node_with_published_page
+    Globalize.with_locale(:de) { node.head.update!(:title => "First") }
+    first_head = node.head
+    find_or_create_draft(node, @user1)
+    Globalize.with_locale(:de) { node.draft.update!(:title => "Second") }
+    node.publish_draft!(@user1)
+
+    node.restore_revision!(first_head.revision, @user1)
+
+    action = NodeAction.last
+    assert_equal "publish",   action.action
+    assert_equal "revision",  action.metadata["via"]
+    assert_equal first_head,  action.page
+    assert_equal @user1,      action.user
+    assert_equal "Second",    action.metadata.dig("title", "from")
+    assert_equal "First",     action.metadata.dig("title", "to")
   end
 end