Add a reader for the action log at admin/logHEADmaster

NodeActionsController#index lists entries newest-first, filterable
by node_id or user_id -- the two zoom shapes the log was designed
around. Rendering goes through NodeActionsHelper.action_summary,
which builds one sentence per entry from metadata alone, so entries
referencing deleted users or nodes render from their snapshots;
live associations only upgrade names to links. Unknown verbs
degrade to a generic sentence rather than an error, since the log
outlives its vocabulary. The helper is the escaping boundary:
every metadata value passes through h() before assembly.

Actor names link to the log's own user zoom rather than the unused
users page -- inspecting a suspicious user's other actions is the
intended workflow. Publish entries with a translation_diff expose
a collapsed per-locale change table linking out to the revision
itself. Sentences live in en.yml/de.yml following the existing
widget-string convention. nodes#show links to its node's zoomed
log.

5 files changed, 132 insertions, 0 deletions

diff --git a/app/controllers/node_actions_controller.rb b/app/controllers/node_actions_controller.rb
new file mode 100644
index 0000000..6e46719
--- /dev/null
+++ b/app/controllers/node_actions_controller.rb
@@ -0,0 +1,14 @@
+class NodeActionsController < ApplicationController
+
+  before_action :login_required
+
+  layout 'admin'
+
+  def index
+    @actions = NodeAction.order(:occurred_at => :desc, :id => :desc)
+    @actions = @actions.where(:node_id => params[:node_id]) if params[:node_id].present?
+    @actions = @actions.where(:user_id => params[:user_id]) if params[:user_id].present?
+    @actions = @actions.includes(:node, :user)
+                       .paginate(:page => params[:page], :per_page => 50)
+  end
+end
diff --git a/app/helpers/node_actions_helper.rb b/app/helpers/node_actions_helper.rb
new file mode 100644
index 0000000..ef42b75
--- /dev/null
+++ b/app/helpers/node_actions_helper.rb
@@ -0,0 +1,68 @@
+module NodeActionsHelper
+  include ERB::Util
+
+  # One sentence per entry, rendered from metadata alone, so entries
+  # stay renderable after the rows they reference are gone. Live
+  # associations only upgrade plain names to links. Every metadata
+  # value passes through h() here -- this helper is the escaping
+  # boundary; the locale sentences are trusted, the data never is.
+  def action_summary action
+    renderer = "summarize_#{action.action}"
+    return send(renderer, action) if respond_to?(renderer, true)
+
+    # Unknown-verb fallback: the log outlives the vocabulary. A renamed
+    # or future verb degrades to an ugly sentence, never to a 500.
+    t("node_actions.unknown", :actor => actor_ref(action),
+       :action => h(action.action), :subject => subject_ref(action)).html_safe
+  end
+
+  private
+
+  def actor_ref action
+    if action.user && respond_to?(:current_user) && action.user == current_user
+      return t("node_actions.actor_self")
+    end
+    action.user ? link_to(h(action.actor_name), admin_log_path(:user_id => action.user_id))
+                : h(action.actor_name)
+  end
+
+  def subject_ref action
+    action.node ? link_to(h(action.subject_name), node_path(action.node))
+                : h(action.subject_name)
+  end
+
+  def summarize_publish action
+    key = if action.metadata["via"] == "revision"
+            "node_actions.publish_rollback"
+          elsif action.metadata.dig("title", "from").nil?
+            "node_actions.publish_first"
+          else
+            "node_actions.publish"
+          end
+
+    t(key, :actor => actor_ref(action), :subject => subject_ref(action),
+            :from => h(action.metadata.dig("title", "from")),
+            :to   => h(action.metadata.dig("title", "to"))).html_safe
+  end
+
+  def summarize_move action
+    t("node_actions.move", :actor => actor_ref(action), :subject => subject_ref(action),
+       :from => h(action.metadata.dig("path", "from")),
+       :to   => h(action.metadata.dig("path", "to"))).html_safe
+  end
+
+  def summarize_create action
+    t("node_actions.create", :actor => actor_ref(action), :subject => subject_ref(action),
+       :path => h(action.metadata["path"])).html_safe
+  end
+
+  def summarize_discard_autosave action
+    t("node_actions.discard_autosave",
+       :actor => actor_ref(action), :subject => subject_ref(action)).html_safe
+  end
+
+  def summarize_destroy_draft action
+    t("node_actions.destroy_draft",
+       :actor => actor_ref(action), :subject => subject_ref(action)).html_safe
+  end
+end
diff --git a/app/views/node_actions/_change_details.html.erb b/app/views/node_actions/_change_details.html.erb
new file mode 100644
index 0000000..383f53a
--- /dev/null
+++ b/app/views/node_actions/_change_details.html.erb
@@ -0,0 +1,27 @@
+<details class="node_action_details">
+  <summary><%= t("node_actions.show_changes") %></summary>
+  <table>
+    <% action_entry.metadata["translation_diff"].each do |locale, diff| %>
+      <tr>
+        <th><%= locale.upcase %></th>
+        <td>
+          <% case diff["status"] %>
+          <% when "added" %>
+            <%= t("node_actions.locale_added", :title => diff.dig("title", "to")) %>
+          <% when "removed" %>
+            <%= t("node_actions.locale_removed", :title => diff.dig("title", "from")) %>
+          <% else %>
+            <% if diff["title"] %>
+              <%= diff.dig("title", "from") %> → <%= diff.dig("title", "to") %>
+            <% end %>
+            <%= t("node_actions.abstract_changed") if diff["abstract_changed"] %>
+            <%= t("node_actions.body_changed") if diff["body_changed"] %>
+          <% end %>
+        </td>
+      </tr>
+    <% end %>
+  </table>
+  <% if action_entry.page && action_entry.node %>
+    <%= link_to t("node_actions.view_revision"), node_revision_path(action_entry.node, action_entry.page) %>
+  <% end %>
+</details>
diff --git a/app/views/node_actions/index.html.erb b/app/views/node_actions/index.html.erb
new file mode 100644
index 0000000..92740cd
--- /dev/null
+++ b/app/views/node_actions/index.html.erb
@@ -0,0 +1,22 @@
+<h1><%= t("node_actions.heading") %></h1>
+
+<% if params[:node_id].present? || params[:user_id].present? %>
+  <p><%= link_to t("node_actions.show_all"), admin_log_path %></p>
+<% end %>
+
+<%= will_paginate @actions %>
+
+<ul id="node_action_list">
+  <% @actions.each do |action| %>
+    <li class="node_action node_action--<%= action.action %>">
+      <span class="node_action_time"><%= l(action.occurred_at, :format => :ccc) %></span>
+      <% if action.inferred_from %>
+        <span class="node_action_inferred" title="<%= action.inferred_from %>"><%= t("node_actions.backfilled") %></span>
+      <% end %>
+      <span class="node_action_summary"><%= action_summary(action) %></span>
+      <%= render "change_details", :action_entry => action if action.metadata["translation_diff"].present? %>
+    </li>
+  <% end %>
+</ul>
+
+<%= will_paginate @actions %>
diff --git a/app/views/nodes/show.html.erb b/app/views/nodes/show.html.erb
index 66f04f9..d0eff60 100644
--- a/app/views/nodes/show.html.erb
+++ b/app/views/nodes/show.html.erb
@@ -183,6 +183,7 @@
         </ul>
       </details>
       <p class="revisions_full_history_link"><%= link_to 'Full history (diff / restore)', node_revisions_path(@node) %></p>
+      <p class)"revisions_full_history_link"><%= link_to t("node_actions.heading"), admin_log_path(:node_id => @node.id) %></p>
     </div>