5 files changed, 202 insertions, 4 deletions

diff --git a/app/controllers/events_controller.rb b/app/controllers/events_controller.rb
index a322181d..818459c4 100644
--- a/app/controllers/events_controller.rb
+++ b/app/controllers/events_controller.rb
@@ -65,7 +65,7 @@ class EventsController < ApplicationController
     @event = Event.new(event_params)
 
     respond_to do |format|
-      if @event.save
+      if @event.save_witnessed(:actor => current_user)
         flash[:notice] = t("flash.events.created")
         format.html { redirect_to(safe_return_to(params[:return_to] || (@event.node ? edit_node_path(@event.node) : edit_event_path(@event)))) }
         format.xml  { render :xml => @event, :status => :created, :location => @event }
@@ -82,7 +82,7 @@ class EventsController < ApplicationController
     @event = Event.find(params[:id])
 
     respond_to do |format|
-      if @event.update(event_params)
+      if @event.update_witnessed(event_params, :actor => current_user)
         flash[:notice] = t("flash.events.updated")
         format.html { redirect_to(safe_return_to(params[:return_to] || events_path)) }
         format.xml  { head :ok }
@@ -97,7 +97,7 @@ class EventsController < ApplicationController
   # DELETE /events/1.xml
   def destroy
     @event = Event.find(params[:id])
-    @event.destroy
+    @event.destroy_witnessed(:actor => current_user)
 
     respond_to do |format|
       format.html { redirect_to(events_url) }
diff --git a/app/helpers/node_actions_helper.rb b/app/helpers/node_actions_helper.rb
index 019a9cf7..672dda36 100644
--- a/app/helpers/node_actions_helper.rb
+++ b/app/helpers/node_actions_helper.rb
@@ -23,7 +23,10 @@ module NodeActionsHelper
     "user_deactivate"    => "user-off",
     "user_reactivate"    => "user-check",
     "redaktion_grant"    => "users-plus",
-    "redaktion_revoke"   => "users-minus"
+    "redaktion_revoke"   => "users-minus",
+    "event_create"       => "calendar-plus",
+    "event_update"       => "calendar-event",
+    "event_destroy"      => "calendar-x"
   }.freeze
 
   def verb_icon action
@@ -57,6 +60,7 @@ module NodeActionsHelper
   def action_details? action
     m = action.metadata
     return true if m["translation_diff"].present?
+    return true if m["changes"].present? || m["description_changed"]
     return true if m["title"].is_a?(Hash) && m.dig("title", "from") != m.dig("title", "to")
     %w[author tags template_changed assets assets_changed assets_reordered
        abstract_changed body_changed].any? { |key| m[key].present? }
@@ -92,6 +96,59 @@ module NodeActionsHelper
     items
   end
 
+  def event_changes_list action
+    m = action.metadata
+    c = m["changes"] || {}
+    items = []
+
+    if c["title"]
+      items << t("node_actions.detail_title",
+                  :from => c.dig("title", "from"), :to => c.dig("title", "to"))
+    end
+
+    if %w[rrule start_time end_time].any? { |field| c.key?(field) }
+      items << t("node_actions.detail_event_schedule",
+                  :from => event_schedule_side(m, c, "from"),
+                  :to   => event_schedule_side(m, c, "to"))
+    end
+
+    if c["allday"]
+      items << t("node_actions.detail_event_allday",
+                  :from => t("admin.common.#{c.dig("allday", "from") ? "yes" : "no"}"),
+                  :to   => t("admin.common.#{c.dig("allday", "to") ? "yes" : "no"}"))
+    end
+
+    %w[location url].each do |field|
+      next unless c[field]
+      items << t("node_actions.detail_event_#{field}",
+                  :from => c.dig(field, "from").presence || t("node_actions.event_none"),
+                  :to   => c.dig(field, "to").presence   || t("node_actions.event_none"))
+    end
+
+    if c["tags"]
+      items << t("node_actions.detail_tags",
+                  :from => Array(c.dig("tags", "from")).join(", "),
+                  :to   => Array(c.dig("tags", "to")).join(", "))
+    end
+
+    if c["node_path"]
+      items << t("node_actions.detail_event_moved",
+                  :from => c.dig("node_path", "from") || t("node_actions.event_none"),
+                  :to   => c.dig("node_path", "to")   || t("node_actions.event_none"))
+    end
+
+    items << t("node_actions.detail_event_description") if m["description_changed"]
+    items << t("node_actions.detail_event_coordinates") if c["latitude"] || c["longitude"]
+    items
+  end
+
+  def event_schedule_side metadata, changes, side
+    attributes = %w[rrule start_time end_time].each_with_object({}) do |field, acc|
+      acc[field.to_sym] = changes.key?(field) ? changes.dig(field, side) : metadata[field]
+    end
+    event_schedule_text(Event.new(attributes)).presence || t("node_actions.event_none")
+  end
+
   def translation_changes diff
     case diff["status"]
     when "added"   then [t("node_actions.locale_added",   :title => diff.dig("title", "to"))]
@@ -188,6 +245,12 @@ module NodeActionsHelper
     participant ? link_to(name, edit_user_path(participant)) : name
   end
 
+  def event_ref action
+    event = action.action_participants.detect { |p| p.subject_type == "Event" }&.subject
+    name  = h(action.metadata["event_title"].presence || t("node_actions.unknown_event"))
+    event ? link_to(name, edit_event_path(event)) : name
+  end
+
   def summarize_publish action
     if action.metadata["via"] == "revision"
       t("node_actions.publish_rollback",
@@ -301,4 +364,26 @@ module NodeActionsHelper
     t("node_actions.user_create", :actor => actor_ref(action),
        :target => user_participant_ref(action)).html_safe
   end
+
+  def summarize_event_create action
+    event_sentence(action, "event_create")
+  end
+
+  def summarize_event_update action
+    event_sentence(action, "event_update")
+  end
+
+  def summarize_event_destroy action
+    event_sentence(action, "event_destroy")
+  end
+
+  def event_sentence action, key
+    if action.node
+      t("node_actions.#{key}_on", :actor => actor_ref(action),
+         :event => event_ref(action), :subject => subject_ref(action)).html_safe
+    else
+      t("node_actions.#{key}", :actor => actor_ref(action),
+         :event => event_ref(action)).html_safe
+    end
+  end
 end
diff --git a/app/models/event.rb b/app/models/event.rb
index b8651a81..7726f9bf 100644
--- a/app/models/event.rb
+++ b/app/models/event.rb
@@ -20,8 +20,85 @@ class Event < ApplicationRecord
     title.presence || node&.head&.title || "Untitled event"
   end
 
+  def save_witnessed(actor:)
+    saved = false
+    transaction do
+      saved = save
+      raise ActiveRecord::Rollback unless saved
+      witness_event!("event_create", actor)
+    end
+    saved
+  end
+
+  def update_witnessed(attributes, actor:)
+    updated = false
+    transaction do
+      updated = update(attributes)
+      raise ActiveRecord::Rollback unless updated
+      changes = event_changes
+      witness_event!("event_update", actor, changes) if changes.any?
+    end
+    updated
+  end
+
+  def destroy_witnessed(actor:)
+    destroyed = false
+    transaction do
+      witness_event!("event_destroy", actor)
+      destroyed = destroy
+      raise ActiveRecord::Rollback unless destroyed
+    end
+    destroyed
+  end
+
   private
     def generate_occurrences
       Occurrence.generate self
     end
+
+    def event_snapshot
+      {
+        :event_title => title.presence || node&.unique_name || "##{id}",
+        :start_time  => start_time&.iso8601,
+        :end_time    => end_time&.iso8601,
+        :allday      => allday,
+        :rrule       => rrule.presence,
+        :location    => location.presence,
+        :url         => url.presence,
+        :event_tags  => tag_list.to_a.sort,
+        :path        => node&.unique_name
+      }.compact
+    end
+
+    def event_changes
+      pairs = {}
+
+      saved_changes.except("updated_at", "created_at", "description")
+                   .each do |attribute, (before, after)|
+        key, pair =
+          case attribute
+          when "node_id"
+            ["node_path", { "from" => Node.find_by(:id => before)&.unique_name,
+                            "to"   => Node.find_by(:id => after)&.unique_name }]
+          when "start_time", "end_time"
+            [attribute, { "from" => before&.iso8601, "to" => after&.iso8601 }]
+          when "tag_list"
+            ["tags", { "from" => Array(before).sort, "to" => Array(after).sort }]
+          else
+            [attribute, { "from" => before, "to" => after }]
+          end
+        pairs[key] = pair
+      end
+
+      extra = {}
+      extra[:changes] = pairs if pairs.any?
+      extra[:description_changed] = true if saved_changes.key?("description")
+      extra
+    end
+
+    def witness_event!(verb, actor, extra = {})
+      NodeAction.record!(:node => node, :participants => [node, self].compact,
+                          :action => verb, :user => actor,
+                          **event_snapshot, **extra)
+    end
 end
diff --git a/app/models/node_action.rb b/app/models/node_action.rb
index 82a3ef44..0167762b 100644
--- a/app/models/node_action.rb
+++ b/app/models/node_action.rb
@@ -107,6 +107,36 @@ class NodeAction < ApplicationRecord
   # participant differ:
   #   "target_login" -- flat string, the affected account's login
   #
+  # "event_create" / "event_update" / "event_destroy" (calendar
+  # entries; participants: the Event and, when it has one, its Node,
+  # which also fills the node column. Deliberately not gated --
+  # events reach chapter pages and widgets, never the feeds, and
+  # protection here follows emission, not position).
+  #
+  # Events carry no revisions, so the log is their only history:
+  # every entry holds a full snapshot of the state it produced, and
+  # walking an event's entries reconstructs it. Times are ISO 8601
+  # and the rrule is raw, never humanised -- entries are read in both
+  # locales and event_schedule_text resolves that at render time.
+  #   "event_title" -- flat string; the title, else the node's
+  #                    unique_name, else "#<id>"
+  #   "start_time", "end_time" -- ISO 8601, when set
+  #   "allday"      -- boolean
+  #   "rrule"       -- raw RRULE, when set
+  #   "location", "url" -- flat strings, when set
+  #   "event_tags"  -- array of names, sorted, always. Named apart
+  #                    from the node verbs' "tags", which is a pair,
+  #                    so one renderer cannot mistake the other.
+  #   "path"        -- the node's unique_name, when it has a node
+  #
+  # On "event_update" only, and only when something changed -- an
+  # update that changes nothing records no entry at all:
+  #   "changes"     -- {field => pair}, node_id resolved to paths
+  #                    under "node_path", tag_list under "tags",
+  #                    times as ISO 8601
+  #   "description_changed" -- boolean; prose, flagged not quoted,
+  #                    as abstract_changed and body_changed are
+  #
   # Reserved: "demote" (via "trash" | "depublish") for an explicit
   # depublish workflow, if ever built.
   #
diff --git a/app/views/node_actions/_change_details.html.erb b/app/views/node_actions/_change_details.html.erb
index 2da8bfd5..98e70d8f 100644
--- a/app/views/node_actions/_change_details.html.erb
+++ b/app/views/node_actions/_change_details.html.erb
@@ -17,6 +17,12 @@
         </td>
       </tr>
     <% end %>
+    <% if (event_items = event_changes_list(action_entry)).any? %>
+      <tr>
+        <th></th>
+        <td><%= safe_join(event_items, tag.br) %></td>
+      </tr>
+    <% end %>
     <% (action_entry.metadata["translation_diff"] || {}).each do |locale, diff| %>
       <tr>
         <th><%= locale.upcase %></th>