Create system comments on events

app/helpers/comments_helper.rb

@@ -1,6 +1,6 @@
 module CommentsHelper
   def new_comment_placeholder(card)
-    if card.creator == Current.user && card.messages.comments.empty?
+    if card.creator == Current.user && card.comments.empty?
       "Next, add some notes, context, pictures, or video about this…"
     else
       "Type your comment…"

app/models/card/eventable.rb

@@ -12,7 +12,7 @@ module Card::Eventable
 
   def event_was_created(event)
     transaction do
-      # find_or_capture_event_summary.events << event
+      create_system_comment_for(event)
       touch(:last_active_at)
     end
   end
@@ -43,4 +43,8 @@ module Card::Eventable
         track_event "card_title_changed", particulars: { old_title: title_before_last_save, new_title: title }
       end
     end
+
+    def create_system_comment_for(event)
+      SystemCommenter.new(self, event).comment
+    end
 end

app/models/card/eventable/system_commenter.rb

@@ -0,0 +1,63 @@
+class Card::Eventable::SystemCommenter
+  attr_reader :card, :event
+
+  def initialize(card, event)
+    @card, @event = card, event
+  end
+
+  def comment
+    return unless comment_body.present?
+
+    if comment = find_replaceable_system_comment
+      comment.update! body: comment_body
+    else
+      card.comments.create! creator: User.system, body: comment_body
+    end
+  end
+
+  private
+    REPLACEABLE_EVENTS = [
+      %w(card_assigned card_unassigned),
+      %w(card_staged card_unstaged),
+      %w(card_due_date_added card_due_date_changed card_due_date_removed)
+    ]
+
+    def comment_body
+      case event.action
+        when "card_assigned"
+          "Assigned to #{card.assignees.pluck(:name).to_sentence}."
+        when "card_unassigned"
+          if card.assignees.empty?
+            "Unassigned from #{event.assignees.pluck(:name).to_sentence}."
+          else
+            "Assigned to #{card.assignees.pluck(:name).to_sentence}."
+          end
+        when "card_staged"
+          "#{event.creator.name} moved this to '#{event.stage_name}'."
+        when "card_closed"
+          "Closed by #{ event.creator.name }"
+        when "card_unstaged"
+          "#{event.creator.name} removed this from '#{event.stage_name}'."
+        when "card_due_date_added"
+          "#{event.creator.name} set due date to #{event.particulars.dig('particulars', 'due_date').to_date.strftime('%B %-d')}."
+        when "card_due_date_changed"
+          "#{event.creator.name} changed due date to #{event.particulars.dig('particulars', 'due_date').to_date.strftime('%B %-d')}."
+        when "card_due_date_removed"
+          "#{event.creator.name} removed the date."
+        when "card_title_changed"
+          "#{event.creator.name} changed title from '#{event.particulars.dig('particulars', 'old_title')}' to '#{event.particulars.dig('particulars', 'new_title')}'."
+      end
+    end
+
+    def find_replaceable_system_comment
+      previous_comment, previous_event = card.comments.last, card.events[-2]
+      if previous_comment&.creator&.system? && replaceable_event?(previous_event, event)
+        previous_comment
+      end
+    end
+
+    def replaceable_event?(candidate_event, replacement_event)
+      candidate_event && replacement_event &&
+        (candidate_event.action == replacement_event.action || REPLACEABLE_EVENTS.find { |related_actions| related_actions.include?(candidate_event.action) && related_actions.include?(replacement_event.action) })
+    end
+end

app/models/comment/eventable.rb

@@ -12,6 +12,10 @@ module Comment::Eventable
   end
 
   private
+    def should_track_event?
+      !creator.system?
+    end
+
     def track_creation
       track_event("created", collection: card.collection)
     end

app/views/cards/_comments.html.erb

@@ -1,6 +1,6 @@
 <% if card.messages.comments.any? %>
   <div class="card__detail card__comments">
-    <span aria-hidden="true"><%= card.messages.comments.count %></span>
-    <span class="for-screen-reader"><%= pluralize(card.messages.comments.count, "comment") %></span>
+    <span aria-hidden="true"><%= card.comments.count %></span>
+    <span class="for-screen-reader"><%= pluralize(card.comments.count, "comment") %></span>
   </div>
 <% end %>

test/models/card/closeable_test.rb

@@ -1,6 +1,10 @@
 require "test_helper"
 
 class Card::CloseableTest < ActiveSupport::TestCase
+  setup do
+    Current.session = sessions(:david)
+  end
+
   test "closed scope" do
     assert_equal [ cards(:shipping) ], Card.closed
     assert_not_includes Card.open, cards(:shipping)