Simplify and attempt fix n+1

Author: jamiebenstead

app/controllers/api/school_classes_controller.rb

@@ -90,30 +90,22 @@ def render_student_index(school_classes)
     end
 
     def calculate_unread_counts(school_classes)
-      school_classes.map do |school_class|
-        lessons = school_class.lessons.accessible_by(current_ability)
-        remixes = user_remixes_for_lessons(lessons)
-
-        remixes.count do |remix|
-          remix&.school_project&.feedback&.exists?(read_at: nil)
-        end
-      end
-    end
-
-    def user_remixes_for_lessons(lessons)
-      lessons.filter_map do |lesson|
-        next nil unless lesson&.project&.remixes&.exists?
-
-        user_remix_for_lesson(lesson)
-      end
-    end
-
-    def user_remix_for_lesson(lesson)
-      lesson.project&.remixes&.where(user_id: current_user.id)
-            &.accessible_by(current_ability)
-            &.order(created_at: :asc)
-            &.includes(school_project: :feedback)
-            &.first
+      class_ids = school_classes.map(&:id)
+
+      # Count unread feedback per class in a single query
+      counts_by_class_id =
+        Feedback
+        .joins(school_project: { project: { lesson: :school_class } })
+        .where(
+          read_at: nil,
+          projects: { user_id: current_user.id },
+          school_classes: { id: class_ids }
+        )
+        .group('school_classes.id')
+        .count
+
+      # Return counts in the same order as school_classes
+      school_classes.map { |school_class| counts_by_class_id[school_class.id] || 0 }
     end
 
     def find_or_create_school_class(school_class_params)