Simplify chapter retrieval for new stories

lib/fic_tracker/models/story.rb

@@ -1,5 +1,6 @@
 # frozen_string_literal: true
 
+require 'digest'
 require_relative 'light/tag'
 
 module FicTracker::Models
@@ -80,7 +81,7 @@ module FicTracker::Models
           end
           to_keep << aut unless id
         end
-        to_remove.delete aut.id if id
+        to_remove.delete aut.id
       end
 
       if id
@@ -107,6 +108,7 @@ module FicTracker::Models
       latest_chapter_at = self.published_at || Time.at(0)
 
       to_add = []
+      to_keep = []
       to_remove = self.chapters.map(&:id)
 
       entries.each do |entry|
@@ -117,8 +119,9 @@ module FicTracker::Models
           chapter.set(**entry)
         else
           chapter = FicTracker::Models::Chapter.new(**entry)
-          to_add << chapter
+          to_add << chapter if id
         end
+        to_keep << chapter unless id
         to_remove.delete chapter.id
       end
 
@@ -135,11 +138,13 @@ module FicTracker::Models
 
         update(updated_at: latest_chapter_at) if latest_chapter_at > Time.at(0) && (updated_at.nil? || latest_chapter_at >= updated_at)
       else
-        @chapters = (@chapters || []) + to_add - to_remove
+        @chapters = to_keep
       end
     end
 
     def ensure_fully_loaded
+      return backend.load_full_story(self) unless id
+
       refresh_content
       refresh_metadata
 
@@ -179,7 +184,7 @@ module FicTracker::Models
     end
 
     def etag
-      chapters.select { |c| c.etag }.compact.last&.etag
+      Digest::SHA1.hexdigest(chapters.map(&:etag).join('|'))
     end
 
     def cache_key